I like your enthusiasm for investigating cycling technology and the use of first principles. I own a company that needed to design and qualify (to ISO Std) a QR interface so I am well versed in these interfaces and the forces tested for design approval. I agree that these parts shouldn't be called axles, as they are solely retainers. Based on my experience, the Thru Axle style interfaces do not solely rely on friction to prevent the hubs sliding relative to the dropouts. A quick friction calc would show that there is not enough resultant friction to prevent the hub sliding into contact with the bottom surface of the Thru Axle under mid to high loads. At this point the Thru Axle will be loaded in plain shear. The friction force at the hub interface only really needs to resist axial twisting against bearing forces (which are negligible) and cornering forces, hence why they have low torque figures compared to their thread capacity. The big vertical hits (from jumps or potholes etc) will overpower the clamping friction force created by the TA and simply load it in vertical shear. QR retainers have a greater factor of safety compared to TAs as they have a less safe open dropout design and as such have huge clamping loads to compensate. But the clamping loads are not created from the thread geometry, they are created from the lever and its pull ratio. From memory, Industry standards requires QRs to prevent wheel pullout by around a 200kgf force. This is a huge force! QRs also have hi tensile stainless steel male and female threads to cope with this high loading. Personally, I wouldn't recommend going beyond the TAs torque spec based on QR data as the clamping requirements are completely different and may jeopardise the TAs threads. This is my second alternative opinion on your videos and I am not the type of person to troll videos lol. I think that on all but the basic parts there is usually more going on than meets the eye. Cheers
Thank you for your salient 'common sense based' input.... And proving the old adage that, 'A little knowledge is a dangerous thing'... The different retention characteristics between TA and QR, makes it an apples versus oranges comparison. And secondarily the cross-sectional dimensions of a TA skewer, allows it to 'easily' serve alternative purposes, such as an attachment point for a bicycle trailer, which is not possible with a QR skewer. Lastly it's not trolling when you're making relevant counterpoints. Have a nice day.
Nice comments. I have a feeling that the wider the thru axle the more capable it is at taking axial loads. This does keep the bike stiffer in the wheel and probably let's the wheel perform at its best too.
I think you are leaving a lot on the table - does a Thru axle make your wheel stiffer - No I agree- wheel stiffness predominantly comes from lacing pattern, hub flange width and diameter, spokes, rim design, and some inner hub-bearing design as you pointed out. But what you have left out is that a thru axle is more used as a frame structure than a wheel structure. Where the wheels attach to a frame is a open area that was traditionally not supported and relied on the hub to make it stiff relying on bearing interface - tolerances ect. Many parts working together... therefore a weak spot. The thru axle becomes an extension of the frame as one part - no bearings just one part to secure the drop outs together. This stiffness in the frame from a rider perspective can feel like the wheel is stiffer because it is not flexing under load. your steering tracks better, the back of the bike feels planted. An easy test is to take an old QR fork with a wheel and hold the wheel between your legs and turn the bars - see how everything flexes .. its shocking how much fork legs flex- do the same with a similar fork but thru axle and you will find it flexes much less. Does a Thru Axle make your wheel stiffer? no - but it does make your frame stiffer allowing you to harness more or your wheel stiffness that was always there. YES
the interesting part of marketing is, while they're telling you a 'good news', underneath the rosy garden they are actually trying to clear their shit. Thru Axle is never a predominant factor to achieve stiffness. Thru Axle is important for saving life. But not thru the Thru Axle itself, but the importance comes from fork end with closed loops (no more dropouts) so that your wheel still hang on to fork to the least when your wheel is trying to escape under serious disc-braking or fork twisting. Now then we can talk about stiffness. i'm 100% with you, that 'wheel stiffness' is provided by hub, from bearing setup, to hub, to lacing, to rim and then to tyre. Thru Axle has very minimum contribution to wheel stiffness. In reality, Thru Axle is a camouflage to a long existing problem: disc rubs and unwanted friction loss which is critical for road race and professional cyclists. putting a disc brake fork (for Thru Axle) and a rim brake fork (with dropouts) side by side, it is not exaggerating to say the fork end on disc brake fork is at least double the thickness of the later. The fork itself has to be beefed up for a significant stiffness improvement, that simply can't be achieved by a larger pipe without thicker fork end. In addition, the beefed up portion on a forks is concentrated at one third lower length till disc caliper mount. Still, that's as much as fork manufacturer can do, latest shimano flagship disc brake claimed to provide wider caliper opening (they claimed it is for quick wheel change yes that is very believable). all in all, i'll consider Thru Axle for safety. rest are just complimentary.
It is my belief that disc brakes must have 12,15 or 20mm thru axles in order to get proper structure stiffness for disc brakes. Loads of cheaper bikes still come with open dropout QR. With heavy braking the axle can be pulled from its seat regardless of how hard you go on the QR lever.
Genuinely love all these myths deconstructions, it truly helps in deciding what to buy/use and sort out all the bullshit. I'm kind of a torque maniac on my bike, so each and every bolt is torqued to spec, with my M12 "axles" at 11Nm; it's good to get a bit of confirmation on your part.
Talked about this with Cy from Cotic a few years back when they were considering thru axles for their next hardtails. His take was along the lines of "most people who buy our frames are using hubs with stiff axles so it's a non-issue". Only real benefits are slightly better disc brake caliper alignment stability and safety (as in the wheel can't fall out). Thru axle rear hubs brought smaller bearings with them so reduced durability.
i found that the hub options for 141mm qr are really limited though, so you are forced to use through axles if you want better hubs, for mountain bikes at least
135qr and 141qr hub options are extremely limited, unless you want to drop $500 for a rear hub. That, knurled end caps messing up the dropouts, and brake misalignment are the only issues with 135
Thanks!! I was a little worried that my QR mountain bike with added mid-drive motor might be not as safe as a thru axle, but this video clears that up!
So it doesn't affect wheel stiffness, what about frame and fork stiffness? Axle becomes a structural element of the fork or rear triangle and resists twisting forces. Compare Manitou Circus dropouts, or modern Fox 38 with open dropouts for QR wheels
I think you guys are missing his point. He focuses on the need for clamping tightness throughout the vid for a reason... because the "spot" where the endcap or axle nut (older assemblies) is pressed up against the dropout is the actual theoretical "position" were the integrity of the assembly (wheel mounted by either QR or TA) interacts with the whole system for stiffness (ie fork and frame)...NOT the larger dia of the TA to the outside of that. In the caveats near the end, he points out the TA does provide "extra bracing" against asymmetrical brake loads. So basically what this means is: With dropout torsion, the larger diameter of the TA does help a small amount TO THE OUTSIDE of the clamping surfaces of the fork or frame drop outs...which are usually only 6 to 25 mm in thickness...so again, a very small amount aiding stiffness. The majority of the stiffness, however, is produced at and to the INSIDE of these points.
@@justpedal65 I think you're underestimating the effect of the diameter of the axle (not the clamping bolt) and it's contribution to the stiffness of the whole wheel mounting construction. Motorcycle axles used to be 12 - 15mm in the old days, now they're more like 25mm, this absolutely increased the stiffnes of the construction. Increasing the diameter increases the angular momentum the construction can resist, so the clamping force might not need to be so high as Peak Torque claims. In any case it's bad advice to tell people to use longer tools than advised by the manufacturer, it might cause very expensive damage to your bike.
On my old MTB in the front I have 20mm through axle (RockShox Maxle) and bearings (6804) directly touches the axle. Front wheel also have 15mm and QR adapters and those adapters just press in the bearing from the sides. And the rear wheel is 12mm through axle like in your drawing. Regarding sheer forces on MTB suspension forks usually one leg has spring (metal/air) and other leg has damper and both of them are connected with the thin arch which may flex on rough terrain. And in case of inverted suspension forks axle is the only thing that connects both fork legs.
The problem is that with both an Engineering Degree and a reasonable ability to write meaningful sentences with semi correct spelling and grammar, you can get a much higher paying job elsewhere...
One place I can see a benefit to a large diameter through axle is in the more extreme MTB application, where the axle is also clamped by pinch bolts on the drop out, which should (I think) increase the rigidity of the fork assembly. Also, the latest axle design on RS forks combines a 15mm axle with a cam action QR lever which should help increase clamping load. Awesome video though, thanks.
Great job explaining and illustrating how this all works. Kind of amazing that a lot of people don't understand how the hubs themself are designed to take the load and the thru-axles just clamp.
@@imperialspy3457 thats why i am limitting this argument to people like myself. Generally if theres no (healthy) room for improvement in weight or power or position on the bike, then go for dura ace, 1000g wheelset and ee brakes and so on. But we all know that is mostly not the case.
Peak Torque, thanks for your content! Having seen lots of your videos debunking marketing claims, I've got a question: what would be your perfect bike from engineering point of view, if it were up to you to design such? Could you make a video on that, please?
Perfect for what, whom, when, and at what cost? Engineering is balancing those questions (and many others) for specific outcomes. there's no one right answer to any engineering problem.
@@sepg5084 for what tho? He's shown in his vids he's interested in road, TT and MTB. I'm just trying to highlight the issue with the words 'perfect' and 'engineering' in the same sentence.
I don't think that's case closed. Just done a back of envelope calc and it showed that the thru axle or QR is seeing a higher axial load than the pre tensions you were calculating with your bolt spreadsheet. Once you overcome the pretension the QR will stretch more than the thru axle so in this case the thru axle will make the wheel feel stiffer. With the QR the hub axle end caps will pull away from the inner faces of the dropouts more and allow the wheel to twist.
Weren’t through axles introduced in response to disc brakes pulling wheels out of dropouts? Once you change from a dropout to a hole in the fork end, then the utility of the skewer-type QR is lost: you can’t just drop the wheel out. The through axle simplifies the whole arrangement by making the “skewer” just a single piece of “pipe”.
Thru-axles make a huge difference in resistance to twist. If you've ever ridden a mountain bike with a ~150mm+ QR fork, you absolutely feel the "noodliness" that journos go on about. The extra axial surface from a "thru-axle" makes a difference there...and similarly on rear-sus MTBs, you used see lots of designs where you'd have a four-bar linkage with two disconnected parallel members at the shock which could easily counterrotate, or a train of a million side-loaded bearings to create an esoteric shock curve - there were (and I think still are?) lots of situations where the big 20mm thru-axle formed a proper component of the structure of the frame itself. On a road bike with proper rear triangles, that factor's pretty moot, but a twist-resisting thru-axle fork is still a good idea. I've a Merlin Inferno, which is a weird Chinesium frame with great geometry, and its thru-axle fork actually has a rubber-bunged hole drilled for a rim brake. You'd have to have a custom hub machined, but think of the sheer stance you could get on the spokes with a full-width pair of flanges on a thru-axle!
Exactly my feelings. Author of video, in all respect to his work, unfortunately analyzed incorrect situation around hub, should around the fork. But the bike designers just wanted to match clamping force of QR with TA. They implemented TA to stiffen fork
@@jimbo4203 exactly, this giys far cleverer than i am, but sometimes you look into something so much that you find fault whwn fault simply isnt there Manufacturers spent millions changing to bolt through, they wouldnt have done all the R&D, redesigned everything, bought new machines to make these things it wasnt making their bikes better..simple fact I mean technology gets better, F1 cars dont use steel brakes anymore
When's ths last time you rode trails on your road bike? And then put a 150mm thru axle fork on it and rode the same trail and said yeah that's a way stiffer fork!😂
Surely thru axles are about combatting the huge amount of twist torque that discs exert on the interface between the QR/TA and the dropouts? This can pull the axle out of the open end of the dropout, so that is closed and stiffened with thru axels.
Another amazingly informative video - one which I have sent to a number of people who I failed to convince that the skewers offered no part in the mechanical loading (other than clamping). I still prefer thru "axles" though. They're a little more fiddly for thieves, but mainly because they make it impossible to misalign a wheel. I've seen QR clamped wheels offset numerous times where the owners have not seated the actual axle properly in the dropout. You can't do this with a thru shaft. And whilst a 5mm QR might be able to offer more clamping force, any thru shaft can provide sufficient amount of clamping.
My word...GREAT to hear someone use the crucial lexicon "load path" with facility. My first professional days on the job (1976) I heard a bearded, grizzled vet use that term in dismissing poorly thought out structural reviews.
One advantage of 'through axles' is your wheel doesn't fall off if they come loose. Much prefer the allen bolt type than qr bolts. They may not add stiffness to the interface between the hub and the frame but they seem to improve frame and fork stiffness especially on inverted forks and Horst link frames. I wouldn't want to go back to 9mm qr on an mtb.
Thanks for the education. First was under the impression that the axle provided load bearing and then I upgraded from a QR specific wheel to a 12mm wheel with end caps and realised that was bunk. I was finding that this set up was loosening up by itself over time but I guess I wasn't applying enough clamping force. Was worried I would break it or mess it up if I put too much load on the QR skewer
What about the fact that in a thru axle interface the dropout is enclosed as opposed to open with qr, would that not limit slippage too resulting in a stiffer interface?
How do quick release and thru axles compare to lateral loading of the fork? I seemed to always get disc rub with an older QR fork I had, but with a thru-axle it's less. Not a good comparison by any means, but I'm still curious of your thoughts on this. Thanks for the content!
How about a standard 15mm end cap hub on a Rockshox fork with the oversize Torque Cap drop outs? When the smaller (standard) end caps are seated into the over size (Torque Cap) drop outs the whole thing flops around until the 15mm thru-axle is located, so in this case, is it fair to say that the axle is taking the vertical loads because the end caps do not mesh in any way with the fork drop outs?
Sure would be nice to see a compression load cell set up to show what kind of clamping forces are actually generated, across TA and QR. Cams are most definitely not all made the same; please consider an appendix with some demonstration, pls? It'd be really nice to have a table of clamping force to brand/model of QR skewer. Those of us with alu endplates would be most appreciative. Also, I've a QR disc frame yet to build and would love to be armed with the facts.
Thank you for a thoughtful and useful analysis. Your point is taken re stiffness of hub but my thought has been similar to other commenters that the TAs improved geometric stiffness of the fork and also but to a lesser degree the rear triangle. I would be very interested in seeing you apply the same orderly presentation format to fork and frame behaviors with the various "axle" types. I stumbled upon this vid on my quest to replace front and rear hubs on the matched pair of hard tail MTBs that my wife and I have. The MTB market has become so segmented that I don't see anything new that is adequate across the versatile range of riding we do. Certainly see new bikes superior at specific things but we need adequate at everything. Anyhow, all else was spec'd well except the cone bearing hubs. We don't need high end hubs but we do need upgrade to sealed cartridge bearings. Some of our riding encounters contamination that too easily bypasses seals of a cone system. Even when new these hubs had the sounds and friction as if the bearings were river pebbles. If anyone has a recommendation for a cartridge bearing hub set that isn't priced like aircraft parts I'd be very appreciative for the input. Bike is 100 front and 135 rear QR. Rims are 32 hole. Brake disks are 6 bolt. Cassette is 9 speed Shimano/SRAM. Sorry for moving off topic but the community attracted to this vid includes the people I think would have good recommendations.
I see through axles primarily as locating the disk precisely so that the pads don't rub. It would be rubbish if every wheel install required a caliper adjustment. I didn't know about the DT 350. They must have been desperate to save weight at the bearing's expense.
Even with a 12 mm through axle you can insert the wheel at an angle and get disc rub. So the solution is simple and applies both to QRs and thru axles - before tightening the axle, set the bike on the ground to fully engage the dropouts. That way you get very simple repeatability and the same wheel location every time. Which affects not just the (disc) brakes (it will affect rim brakes as well of course, they are just a bit more quiet when rubbing), but your shifting too.
@@Primoz.r exactly. i never understood how exactly people don't have the repeatability of brake location with qr. you just sit the wheel to the ground tyhe rear axle sits on the dropouts and you tighten. this rubbing problem didn't seem to exist befora thru axles came around, so i consider this rubbing old issue, just a marketing hype to sell the new type of product
I have 4 bikes with QR and disc brakes and no issues in locating the wheel for rub free brakes. 2 have front through axles and have had both rattle loose, I have to force tgem so tight I'll need a rock as a hammer to get them loose if I have a puncture that tge tubeless and plugs don't sort. My FS Epic is QR front but has big diameter end caps and this is stiffer than my rigid MTB with a front through axle. Most small developments are just to get you to spend on a new bike.
@@moo4rich I'm no engineer. That's why I kept my opinion to myself. But I kept thinking throughout this discussion why one would not simply place larger diameter end-caps on the quick release skewers. Does that make sense in any way? Were told, don't you dare use quick release frames with disk brakes. Doesn't seem to hold water, that argument.
I really appreciate your effort in your videos I have got a question. Where do you geht the CAD Models? Do you measure them and build them yourself? Or do you get them from the Web? Best regards Ballermän
you should have more views. Finally someone that says everything as they trully are.I myself have found that actually the old threaded axle provide the most clamping force and actually adds rigidity to the frame. Well done.
Dont mistake clamping force for stiffness of the fork. Anyway, i love my fox floating axles. Very precise wheel alignment, same clamping force as a QR, and fast removal (approx 5secs). On an MTB they make a lot of sense!
The through axle is designed to make the fork or frame stiffer, regardless of the hub. Greater fork or frame stiffness is transferred to the hub for better tracking of the wheel. The small axle end area of a qr combined with narrow dropouts and flexible qr allows the hub/fork to flex in relation to one another. It's not about vertical movement of the mating surface, it's about flexibility. Apply a side load to a rim and measure deflection.
Thru axle: it is a part that goes through the axle... Misleading name? Not an axle itself but is does describes what the part does... (or am I just being smart now....)
If that's what the name means, then a quick release is also a through axle. But since a quick releases aren't called "through axles", that must not be what the name means.
A number of years ago I was repairing a carbon mtb frame for one of the local jr racers. He had crashed on it and broken a seat stay clean through. When he brought the bike to me with the wheel installed 12X48 Boost the two parts of the seat stay did not line up. When I removed the thru-axle and wheel the two parts lined up perfectly. That told me that the actual thru-axle system had enough beef to it for it to correct any mis-alignment in the drop outs not being parallel to each other. So just another way for the manufacturers to hide their poor quality control. Overall you are so correct in a larger bolt needing a higher amount of torque to achieve the same clamping force. As well as the axle not being part of the load path. Thank you. I have been preaching all of this for a while now.
30 years ago linkage forks were a thing. The attempted goal being to keep the fork arms parallel and even. The molded crowns on the one piece lowers were getting bigger and bigger but one sided springs made everything sloppy. When thu-axles appeared it was a game changer to add some moment distribution at the lower fork.
Did you know that all modern high end telescoping suspension forks, single crown, double triple crown all have their spring media in one leg and their damping systems in the other? One side trying to always extend and the other side damping slow speed, high speed compression and rebound circuits. 30 years later we have got the sloppy out of single sided springs. And all that is old is new again, crazy huge carbon leading and trailing link forks are trying to come back. www.pinkbike.com/news/structure-cycleworks-linkage-fork-crankworx-whistler-2017.html and now killed by covid19 bikerumor.com/2018/10/25/trust-performance-sends-the-message-brings-linkage-suspension-forks-to-the-forefront/
The next test should be to measure the axle deflection while mounted in an mtb fork. Not sure that it would matter on a rigid fork. I like thru-axle on my road bike because I can put the wheels on when it is in the workstand. Makes me happy every time.
I like TA over QR because I think it does a much better job at holding the disc brake interface in place, so you get much less brake pad/rotor rubbing and scratching, especially when cornering.
Question: Ti skewers are often said to give a "noodly feeling" and cause more brake rub due to the lower Young's modulus compared to steel, but if there are no signs of slipping in the dropouts, how can this be so? I suspect it's bs but, is it possible that the lower clamping force allows a bit of movement so that the the end-caps are momentarily off parallel with the drop out, but without full blown slippage occuring.
I stopped using a Ti QR skewer on the rear wheel on my bikes and the brake rub is away. Don’t think it’s the titanium’s fault used in the axle but the lack of material/strength in the aluminium end caps (I used PlanetX Ti skewers). I’m able to wobble the rear wheel with my hand after doing them up fairly tight (try it). If so go back to standard manufacturer spec, where there’s a lot more material in the end caps, which spreads the load better and clamping force is stronger. It doesn’t pose a problem at the front though...
This is a good question. I always assumed it was because of the lower Young's modulus combined with a the higher elastic limit of titanium. Once Young's modulus is exceeded through lateral stress, the rider feels a "noodly" change at the axle, but once the stress is removed (such as straightening out after a hard turn or slowing after a hard sprint) the titanium skewer returns to its original dimensions and the "noodly" feeling goes away. Would be difficult to test in a laboratory setting tho, considering the magnitude of the forces involved.
I use titanium 5mm skewers and have had no issues whatsoever, but they have an Allen end on them, not a QR lever. The titanium hex head is annoying actually because it's softer than steel so I'm always worried about rounding it if I overtighten. Been using them over a year, no problem. I weigh over 85kg and can put out a fair bit of power in a sprint.
@@yonseimatt yeah, you can probably achieve the same clamping force as a steel skewer but the problem would be resisting any additional load in the skewer. As monsterinyourcloset says it may be difficult to test. A camera fixed on the rear stays for some sprints might reveal something.
Very interesting, in essence then the advantages of TA are more precise alignment and MAYBE some increased frame stiffness due to the precision of the interface which does not rely solely on the clamping force to keep the axle in position. If you forget to tighten your QR things can be pretty dire but even a slightly under tensioned TA will still keep your wheel from falling out.
Hi. Could you please explain how is the clamping torque affected by the Rockshox screw-in + lever "through-axle" system for front forks? The bolt torque itself is quite low as there is only a short lever, but then the lever cam is used to push a wedged element into the "through axle"'s non-disc side interior, and this expands the through-axle and makes a pressure-contact with the non-disc fork leg's "thru-axle hole". I was wondering if this cam system's purpose is only to prevent accidental unscrewing of the "through axle" (which could be possible due to the rather low clamping force attained from the threads due to the short lever) by creating a "friction lock", or if it maybe also provides additional clamping force? I always screw it in quite hard, but the way the rotating lever interfaces with this alu slot in the thru axle suggests that the axle is intended to be screwed in with quite low torque (sort of let's say a few Nm), and then somehow clamped... I guess I could always make an experiment - screw it in so that the wheel has some play and then set the cam up so that it will lock it in place, and see if the play is reduced/gone - but I never tried that yet.
I really love smart people. It is how we all learn and discover and advance. Although in this case I think some cyclists think of stiffness in the fork differently . I understand the vertical force. We get reminded with every bump in the road. I think when some cyclists refer to stiffness it is in the idea of rotational forces. Feeling the fork twist? That wiggle wabble? Sure I understand with load and force and directions but as much as forks and or dropouts skewers, axles and such, how can the twisting feel be improved and will a axle improve strength or resistance in that direction. Should we steer more towards hub upgrade? Especially for the swarm of adventurers strapping loads to the front of forks. Thank you.
Peak Torque, can you make another America's Cup video please? Some good engineering analysis on the Mozzy Sails channel but keen to see another Peak Torque video on their aero packages now the boats have all added new fairings and shrouds.
Through axle doesn’t make the wheel/hub stiffer. It makes the fork stiffer. The chassis flexes less therefore you track better. Axles would bend constantly if they took weight on a mtb it’s only job is to clamp the wheel to the bike. Very good and scientific overview!
You sir are my hero. Subscribed! I have designed automotive beam axles and use joint calculators alot! Just getting more into bikes and was hearing alot of misinformation on thru axles vs QR. I agree with you that they are just a bolt to provide clamp load on the joint and not part of the load path.
Thanks to youtube algo and your yet another cycling myth busting. It saved me from from diving into through axle part. I have RAF 13 front hub. I don't like QR hanging around. What would be the impact on stiffness if I just use small bolts to tighten instead of QR please
Hey love your videos! Just wondering, is the real axle of thru axle hubs larger in diameter than the axle on a qr? If so why would that not make it stiffer? I'm not personally invested, seeing as I'm sticking to qr either way, I'm just curious. I'm also curious about bolt on axles? Where do they lie in this comparison?
I'm an electrical engineer, not a mechanical engineer, so this was extremely helpful and insightful. Your analysis all makes sense. I had visualized what you have described here as the possible strength dilution but I didn't have the formulae or analysis to prove it to myself, so thank you. BUT given this awesome analysis, would the forces on wheels, the rigid fork, and the seatpost be unidirectional enough to make the use of carbon fiber in these parts a good place to save weight?
Fascinating explainer, I have questions. Understanding that the end cap/dropout interface needs to be well clamped and accepting that the 4nm clamping force provided by the DT key in the field is going to be far less that of a QR skewer, have manufacturers already factored this in? eg at 4nm hand tight are we getting as stiff as is required, the end cap is not loose in the dropout and will not shift, and it is limited gains beyond this? Secondly, is there any effect on material fatigue, do higher clamping forces tension the forks or rear stays in a different way that may be worth considering?
I'm old school and still use Shimano QR as I believe they give the highest clamping pressures. Always thought thru axles were a con unless they could be tightened enough. Need to carry a FO Snap-On/Park torque wrench in your saddle bag just in case you need to get the wheel out and then refit out on a ride.
I really like watching your videos, you know what you’re talking about 👍. 2 pointers for future experiment/video to mention.1st - the lever in thru axle is quite small to put a lot of torque through it (you mention 4NM), but are the threads in the fork blade really strong enough to take more than 10-15 NM. Perhaps the small lever provided is protecting the threads from being over-tightened by the user and hence shredding the threads and the need to replace the whole fork. Could you investigate what load would the treads take without damage... 2nd - it’s a fact that many cyclists do their quick release skewers to different tension (some - too loose and some - too tight, that you struggle to even undo the lever) and this affects preload on bearings/end caps/fork etc. differently, but also affects brake pad clearance in a hydraulic disc brakes. I converted my TRP Spyre mechanical disc brakes to BR RS785 hydraulics and I can notice that the pad clearance in hydraulic disc brakes is much much smaller with less adjustability compared to old setup. It’s therefore very sensitive to QR skewer preload tension and repeatability of the same tension... Hope this makes sense, keep up the good work 👍
I know it is an old comment. The common misunderstanding of function of QR leads people to false conclusion that amount of tension put in skewer somehow affect alignment of disc brakes. QR is there only to put enough preload to hold the wheel in droupouts by friction, the alignment is done by geometry of fork/frame itslef. Bike manufacturers fucked up the concept and made the surface of vertical faces of droupouts and/or hubs serrated. They've probably thought it is a good way to add extra friction into equation. However, this cause misalignment everytime you dismount and mount your wheel because you are unable to hit the previous configuration of dents.
Incredible. I love this video thanks so much. Can I ask, why do you think thru axles are more popular with major brands? Is it actually just more safe because it cant fall out of the drop outs? (Like if you are stupid enough to not tighten your qr and do a jump).
Great video! One comment on the cross section of the rear hub: this is NOT like DT designed their 240. In my opinion it is for a 240 like so: the axial clamping force there is transfered from (right to left): - right endcap - inner race of 1st freehub bearing - spacer ring between the freehub bearings - inner race of 2nd freehub bearing - another spacer ring inner race of right hub bearing - right shoulder of hub axle (so no play there) - left shoulder of hub axle - inner race of left hub bearing - left endcap. There is a gap between the endcaps and the face sides of the hub axle.
Thanks for the video! But could you explain why the same 4nm torque on the M5 QR generates twice the clamping force as the M12 thru-axle? That seems very counter-intuitive.
The 4Nm torque that PT refers to, should be QR lever torque, not a screw tightening torque. This torque on QR, is taking advantage of a cam in the QR, ramping the axial pull on skewer up many folds hence the clamping force. But I believe PT is using the same calculation as M12. For M12 Thru Axle, it is a direct screw torque, hence you really need to tighten it as per suggested by manufacturer to achieve the same and desired clamping force. However, it's a broken system for many niche and unreliable manufacturers, because they either they don't know what they are doing, or they are closing one eye, or both.
@@willo7979 Thanks. I was wondering about that. When I re-played the part where he did the calculation, the only thing he changed was the screw diameter. I don't recall him making any other calculation changes. But I can see what you wrote is the only plausible explanation.
Yes, but with QRs you can have the wheel pull itself out of the drop-outs, if you're unlucky and lock up the brakes (at least on the front), so I'd still say Thru-axles are probably the better choice in that respect.
@@dalailambda9420 unless it's a shitty dropout it's very unlikely to happen. Most of the dropouts for disc brakes with qr have little flanges around the area where the skewer cap goes. Simply said: thats not just flat thing with cutout on the bottom. So even of it's not tight enough the wheel cannot be pulled out. Most of the cases - those flanges are too small (shitty fork/ frame) or non existing (even worse manufacturer or some improper conversion to disc brakes) - or (worst case) somebody didn't check if the skewer are clamped properly.
The main problem with QRs not clamping wheels strongly enough, is that so many people don't know how to tighten them properly, in the way they were meant to.
If you do them up to the recommended 10Nm then yep. If you get the ones with the built in lever, the lever clicks round once you hit 10Nm, it’s effectively a built in torque wrench. Clever design.
I tend to agree with the theory that a thru axle , and the bracing needed now on the front fork due to needing a stronger fork mount for the force placed on that area by the braking calipers in that area , has now removed the natural springing in the front fork which really has a lot to do with ride comfort. My vintage Raleigh Super Course had an amazing ride. I gave it away and now recently bought a vintage Raleigh Super Course MK ll with beautiful curved fork. I am servicing all the hubs, crank, head set and looking forward to the ride. The bike industry is just to geared towards changing things right now.
Really make sense M12 decreases the force amplification of the built-in clamp lever compared to M5 to get the desired or max torque. Thank you for sharing your technical knowledge. Great content!
So what would be the ideal solution? Here's my suggestion: 5mm solid thru axle. You get the increased clamping force and repeatability of locating the rotor, with a more easily manufacturable skewer - people could even use their old skewers. Suspect easier to align the frame during manufacturing. Would love to see a follow up also talking about fork stiffness -- the fact that lefty forks exist suggests to me that the thru axle doesn't do much here.
What would be the point of using a qr as a TA? 🤔And why would anyone ever want to use their ancient qr skewers on a brand-new bike? 😂 That makes no sense whatsoever, as it’s the frame and forks which determines if a TA is used. 🤪Moreover, I very much doubt a 5mm TA will have sufficient ability to locate the wheel and disc as there’s just too much play in the threads themselves when they’re such a small diameter.😱
The stiffness that I found with a 12mm bolt vs the qr was actually in rear triangle flex. It’s harder to twist the rear triangle then previously. That was the stiffness I was after. Basically you are calculating just the side to side load on the axle not the whole bike. While I agree you are right when only keeping the axle/wheel loads in mind overall frame the smaller diameter doesn’t seem to provide as much. I don’t know I felt it did more in the department of changing how the rear triangle behaved because the larger diameter prevented frame flex to a degree. The same goes for the forks as well. The “thru axle” is more for connecting the legs then making the tire stiffer.
This video completely missed the frame/fork interface and how a fork with a 10-20mm overlap of the axle will be stiffer than compressing a slotted dropout between the at head and the axle. There is a clever caveat at the end “ not stiff in the way most people think they are” so the actual subject of thru-axles benefits can be ignored
What exactly do you mean when you say a “10-20mm overlap of the axle”? 🤔Exactly which part of the fork is different from currently and what is overlapping what and where? Also, the only person who’s ignoring the benefits of TAs is you. 🤨This video is NOT about the benefits of said axles, it’s whether a TA is stiffer than a qr, which as we’ve seen, it isn’t, in the vast majority of cases. 😳The only thing which has been completely missed is your understanding of what this video is about. 😱It definitely didn’t miss out on anything.🤓
Great material. I always wondered why hub companies do not use the TA as the real axle and put bigger bearings (12mm ID instead of 15mm ID) as the hub axle and TA seem redundant and I did not know DT actually had one hub designed like that. But you are right about the fact that doing it that way you need a very sloppy fit to be able to remove the wheels in the field... Now, I fear that we may see plastic bushings like in the Shimano BB making their way into hubs (or hopefully the Mavic experience with plastic bushings in freehubs was painful enough...)
@OmegaMan I have strong hands, anything up to 20Nm is doable with a short allen key. It will leave a nice red tattoo on your handpalm for sure ;) And you can always lean down with your shoe on the allen key...
I thought, like a motorcycle axle, the idea with a bike through-axel is that it's a very tight fit in the dropouts. Such a close tolerance that no slippage is possible and therefore much less clamping force is necessary. The idea being that it's an axel system that does not rely exclusively on friction resulting from high clamping force to maintain axel position in the dropouts and wheel position. If that's not how they work, guess what kind of modification I would make first?
The term stiffness comparison of thru vs qr based on clamping force comparison is selective analysis. The diameter of thru axel hubs vs diameter of qr hub caps against the fork is more relevant. Though contact surfaces of hub cap against mating parts is far more significant for fork, versus the rear dropout. Hence caad qr rear.
Who mentioned friction? Surface area. Torque Caps, for example. Bracing angles? And why are you calling them thru-axles when it’s a bolt through, let’s not perpetuate a myth.
@Pablo Morales qr bikes always have paint chipping off the dropouts... bolt through doesnt.... Amount of times ive had to removed deformed paint from qr dropouts...never had to with BT
@Pablo Morales My QR bikes does have some carbon or metal eaten in the dropouts. not to the point of failure but it has some because there's high pressure in this points. The pressure is more distributed in the case of a thru-axle.
I’m pretty sure the thru axle was never meant to add wheel stiffness or vertical stiffness. It reduces compliance when leaned over as it helps to maintain the 90 angle between axle and fork leg. Basically preventing it from going parallelogram. As the loads on a MTB are often off center because the tire is wider, these side loads are more common and the thru axle is more important. Road bikes become more responsive when really pumping As you’re not twisting the fork.
It took me almost a decade to jump on the thru axle bandwagon in MTB. Going from a dirt jump qr fork (massive crown) to enduro thru axle forks I could not tell the difference. I'm thinking what people were actually feeling were wheel and fork design changes.
Ive had 2 sets of the same wheels 1 was qr one was bolt through BT was far more rigid Forks were the same (qr version amd BT version) BT feels noticeably superior, if you cant tell the difference there is something wrong.... Next people will be saying running a 23mm tire and a 28mm tire feel the same
@@karl8805 While thinking it's the wheel that makes the diff. Have you ever thought that that the fork end on your BT fork is forming a close loop (compared to a QR fork) and that should be given some credit too, if not completely?
Thank you. I always had this suspicion, but never had the knowledge to prove it. Never felt any difference to qr, in fact when I was a bike messenger I had really low atc fork, the 22mm tires the bike came with just barely cleared at the top, soon I had to change tires and I could only get 23s, so I had to lift up the bike a bit before clamping down the qr, so the axle wasn't all the way in the dropout. And I rode like that for months thru cobble stones, endless potholes, speedbumps, jumping up and down curbs, drafting behind buses, doing 90-100 km a day and it didn't move once.
Most normal people wouldnt be able to tell the difference....i can Same with these idiots that say 105 feels the same as ultegra when it clearly doesnt
I think that’s what the clamping is that he’s talking about. The problem is how to get it tight enough. The DT Swiss lever he mentions doesn’t have enough leverage.
@@johnegregg I don't think that's what he's referring to. I think what he's talking about is the ability to create a good interface between one side of the dropout and the hub flange. Not about attempting to unify the dropouts into a single construct. Because with what he's talking about, the QR accomplishes it more effectively to and I'm going to have a really hard time reasoning that a QR more effectively unifies one dropout to the other. Maybe the reason that thru axles can get away with shorter levers is that they don't need to be as tight as QR's to accomplish what I'm talking about as effectively.
I think you misinterpreted the fact that a thru axle provides less clamping force: that means it's stiffer so less force is required, as some have said, it's an extension of the frame and adds structural integrity, keep in mind that it sits flush inside the real axle, with no play, and it remains locked with it.
Great explanation! Any idea what torque setting pro mechanics use on their impact drivers for road disc wheel T-As? I imagine they’ll use the same regardless of whether they’re on the road or in the service course
Totally agree about the load path and how the thru axle doesn't add anything to the stiffness really. But there's something odd about the bolt calculation: why would a larger bolt give a lower clamping force with the same torque?
Does thru axle maybe provide more stiffness in the fork itself as it is screwed into the fork and not just clamping? could that be some stiffness people relate to?
I'd contend that the actual axle on the DT 350 front is a combination of the center sleeve, bearing inner races, and end caps. All are held in position by surface friction and the thru axle still doesn't necessarily contact the bearing or all other parts.
@@n0ch91c3s I agree with you. However this sounds a little bit strange. Something should wear the loads come from the front wheel, I think that friction between the edges of the spacers - bearing inner races - inner spacer - sleeve would be not enough.
A thing I'd like to see addressed though is the stiffness of a suspension fork with 5mm vs 15mm. Surely it's the larger clamping surface diameter you get with a bigger thru bolt that contributes to the stiffness? I'm sure I'm not explaining it very well, but when Marzocchi made their first USD fork (Shiver, IIRC?) they specced a large diameter thru bolt, I think 20mm, because anything smaller made it feel noodly. I guess it makes little difference with the rear dropouts as they're one corner of a triangle anyway so not subject to moving away from each other they way that the more independent legs of a fork are.
Torque caps (the sram standard for MTB) I think “proves” this as well. I imagine the larger surface area of the torque cap helps increase stiffness by making it harder to rock (due to the larger supported diameter). What are your thoughts on torque caps? However I always thought the QR partially relied on the nipple of the end cap sitting in the dropout. Typically when installing the hub in the frame/fork I would make sure these “nipples” were bottomed out on the dropout before tightening the QR. thus the typical vertical-ish loads can be taken by the normal, and the friction. That’s why QRs can be ridden with the QRs being pretty loose. Which is probably one of the things that has lead to the lawsuits and thus the death of qr.
"Lawyer tabs" yes, are there to prevent the wheel falling out in case where the QR is loose. QR's are not going away because they are unsafe, but because the manufacturers and marketing folks are brainwashing us to buy something different.
My brother went to a bike park a few months back. He had a blast ripping his side knobs off his tyres. As he went back home he realized, that his draw bolt came lose. He replaced it afterwards. With a lose QR he probably (almost certainly) would have lost his wheel, and would have been seriously injured. The main benefit to through axles is that you can not lose them so easily and the disc-caliper alignment is really good.
I do own a Chris King hub(disc) R45. So on the rear hub I struggled to find the right torque necessary to make the end cub to the Hub axle. If you leave it to loose it will leave the wheel with a wobbly effect (regardless of the torq applied on T. Axle). But I notice if you apply ther force necessary to not have the wobbly it take quiet a lot of torque but then I feel the bearings being squashed to the point I can turn the cassette in the opposite side just turning the wheel axle with my fingers. For some reason I find this very poor design. Hopefully I am wrong here. Correct me if I am wrong. Is it not better rely on QR or TA torq force on the end caps rather than have two different sistem applying force in the bearings!?.doesn’t affect the performance of the bearings!?
Your joint calculator assumes solid cross section and material properties. Question: Having never built a bike, are thru axle bolts and QR bolts a solid cross section or hollow? And is the material similar to grade 8.8? Just want to make sure.
I like your enthusiasm for investigating cycling technology and the use of first principles. I own a company that needed to design and qualify (to ISO Std) a QR interface so I am well versed in these interfaces and the forces tested for design approval. I agree that these parts shouldn't be called axles, as they are solely retainers.
Based on my experience, the Thru Axle style interfaces do not solely rely on friction to prevent the hubs sliding relative to the dropouts. A quick friction calc would show that there is not enough resultant friction to prevent the hub sliding into contact with the bottom surface of the Thru Axle under mid to high loads. At this point the Thru Axle will be loaded in plain shear. The friction force at the hub interface only really needs to resist axial twisting against bearing forces (which are negligible) and cornering forces, hence why they have low torque figures compared to their thread capacity. The big vertical hits (from jumps or potholes etc) will overpower the clamping friction force created by the TA and simply load it in vertical shear.
QR retainers have a greater factor of safety compared to TAs as they have a less safe open dropout design and as such have huge clamping loads to compensate. But the clamping loads are not created from the thread geometry, they are created from the lever and its pull ratio. From memory, Industry standards requires QRs to prevent wheel pullout by around a 200kgf force. This is a huge force! QRs also have hi tensile stainless steel male and female threads to cope with this high loading.
Personally, I wouldn't recommend going beyond the TAs torque spec based on QR data as the clamping requirements are completely different and may jeopardise the TAs threads.
This is my second alternative opinion on your videos and I am not the type of person to troll videos lol. I think that on all but the basic parts there is usually more going on than meets the eye. Cheers
Thank you for your salient 'common sense based' input.... And proving the old adage that, 'A little knowledge is a dangerous thing'...
The different retention characteristics between TA and QR, makes it an apples versus oranges comparison. And secondarily the cross-sectional dimensions of a TA skewer, allows it to 'easily' serve alternative purposes, such as an attachment point for a bicycle trailer, which is not possible with a QR skewer.
Lastly it's not trolling when you're making relevant counterpoints. Have a nice day.
Nice comments. I have a feeling that the wider the thru axle the more capable it is at taking axial loads. This does keep the bike stiffer in the wheel and probably let's the wheel perform at its best too.
I think you are leaving a lot on the table - does a Thru axle make your wheel stiffer - No I agree- wheel stiffness predominantly comes from lacing pattern, hub flange width and diameter, spokes, rim design, and some inner hub-bearing design as you pointed out. But what you have left out is that a thru axle is more used as a frame structure than a wheel structure. Where the wheels attach to a frame is a open area that was traditionally not supported and relied on the hub to make it stiff relying on bearing interface - tolerances ect. Many parts working together... therefore a weak spot. The thru axle becomes an extension of the frame as one part - no bearings just one part to secure the drop outs together. This stiffness in the frame from a rider perspective can feel like the wheel is stiffer because it is not flexing under load. your steering tracks better, the back of the bike feels planted. An easy test is to take an old QR fork with a wheel and hold the wheel between your legs and turn the bars - see how everything flexes .. its shocking how much fork legs flex- do the same with a similar fork but thru axle and you will find it flexes much less.
Does a Thru Axle make your wheel stiffer? no - but it does make your frame stiffer allowing you to harness more or your wheel stiffness that was always there. YES
the interesting part of marketing is, while they're telling you a 'good news', underneath the rosy garden they are actually trying to clear their shit.
Thru Axle is never a predominant factor to achieve stiffness.
Thru Axle is important for saving life. But not thru the Thru Axle itself, but the importance comes from fork end with closed loops (no more dropouts) so that your wheel still hang on to fork to the least when your wheel is trying to escape under serious disc-braking or fork twisting.
Now then we can talk about stiffness. i'm 100% with you, that 'wheel stiffness' is provided by hub, from bearing setup, to hub, to lacing, to rim and then to tyre.
Thru Axle has very minimum contribution to wheel stiffness.
In reality, Thru Axle is a camouflage to a long existing problem: disc rubs and unwanted friction loss which is critical for road race and professional cyclists.
putting a disc brake fork (for Thru Axle) and a rim brake fork (with dropouts) side by side, it is not exaggerating to say the fork end on disc brake fork is at least double the thickness of the later. The fork itself has to be beefed up for a significant stiffness improvement, that simply can't be achieved by a larger pipe without thicker fork end. In addition, the beefed up portion on a forks is concentrated at one third lower length till disc caliper mount. Still, that's as much as fork manufacturer can do, latest shimano flagship disc brake claimed to provide wider caliper opening (they claimed it is for quick wheel change yes that is very believable).
all in all, i'll consider Thru Axle for safety. rest are just complimentary.
It is my belief that disc brakes must have 12,15 or 20mm thru axles in order to get proper structure stiffness for disc brakes. Loads of cheaper bikes still come with open dropout QR. With heavy braking the axle can be pulled from its seat regardless of how hard you go on the QR lever.
@@kevinwells1660 walmart bike does not fulfil requirement as mountain bike, although they look like one.
@@willo7979 some of the "leading brands" still sell open dropout MTB shaped bicycles, road bikes also.
@@kevinwells1660 hmm... ok
Let’s demand them to admit their fault, refund or replace shall we?
"Dude, why's it called thru-axle?"
"It goes through the axle of the bike."
"So it kinda like skewers the axle?"
"Yeah pretty much..."
PT makes me the stiffest of any UA-cam bike engineer. Source: Hambini's recent Grindr survey.
I just watched that same video last night as well.
Apparently he packs a big wrench
PMSL
@@Hambini shhhhh Varah
In conclusion a bigger axle isn't always stiffer.
That's 3 years of intensive research on cornhub... Here you go, some have to make sacrifices.
2.2 hundred kilos, also known as 220 kilos haha. Sticking with your chosen unit like a good engineer.
Stubborn twat!
Genuinely love all these myths deconstructions, it truly helps in deciding what to buy/use and sort out all the bullshit.
I'm kind of a torque maniac on my bike, so each and every bolt is torqued to spec, with my M12 "axles" at 11Nm; it's good to get a bit of confirmation on your part.
Talked about this with Cy from Cotic a few years back when they were considering thru axles for their next hardtails. His take was along the lines of "most people who buy our frames are using hubs with stiff axles so it's a non-issue". Only real benefits are slightly better disc brake caliper alignment stability and safety (as in the wheel can't fall out).
Thru axle rear hubs brought smaller bearings with them so reduced durability.
i found that the hub options for 141mm qr are really limited though, so you are forced to use through axles if you want better hubs, for mountain bikes at least
Cotic. Engineers 👍
135qr and 141qr hub options are extremely limited, unless you want to drop $500 for a rear hub. That, knurled end caps messing up the dropouts, and brake misalignment are the only issues with 135
Thanks!! I was a little worried that my QR mountain bike with added mid-drive motor might be not as safe as a thru axle, but this video clears that up!
So it doesn't affect wheel stiffness, what about frame and fork stiffness? Axle becomes a structural element of the fork or rear triangle and resists twisting forces. Compare Manitou Circus dropouts, or modern Fox 38 with open dropouts for QR wheels
you'd just pointed it out, left and right sides of forkends became a rigid piece linking by this rod therefore the forks is stiffer.
when fork is stiffer, left fork twists less upon disc braking, thus caliper will have less chances to cause disc warp perhaps.
Thank you. I was hoping someone would point this out.
I think you guys are missing his point. He focuses on the need for clamping tightness throughout the vid for a reason... because the "spot" where the endcap or axle nut (older assemblies) is pressed up against the dropout is the actual theoretical "position" were the integrity of the assembly (wheel mounted by either QR or TA) interacts with the whole system for stiffness (ie fork and frame)...NOT the larger dia of the TA to the outside of that. In the caveats near the end, he points out the TA does provide "extra bracing" against asymmetrical brake loads. So basically what this means is: With dropout torsion, the larger diameter of the TA does help a small amount TO THE OUTSIDE of the clamping surfaces of the fork or frame drop outs...which are usually only 6 to 25 mm in thickness...so again, a very small amount aiding stiffness. The majority of the stiffness, however, is produced at and to the INSIDE of these points.
@@justpedal65 I think you're underestimating the effect of the diameter of the axle (not the clamping bolt) and it's contribution to the stiffness of the whole wheel mounting construction. Motorcycle axles used to be 12 - 15mm in the old days, now they're more like 25mm, this absolutely increased the stiffnes of the construction.
Increasing the diameter increases the angular momentum the construction can resist, so the clamping force might not need to be so high as Peak Torque claims.
In any case it's bad advice to tell people to use longer tools than advised by the manufacturer, it might cause very expensive damage to your bike.
i think you missed the forest for the trees. isn’t the issue more of the interface of the hub and dropout?
I believe he says the end cap is the interface of the hub in the dropout, and it makes sense, QR couldn't exist otherwise.
Hallelujah! Finally, an engineering analysis not a marketing pitch. Nicely done.
Love the complete lack of fluff and BS in these videos. Breath of fresh air!
Very interesting. Now if you excuse me, I'll be on my way to tighten some axles.
On my old MTB in the front I have 20mm through axle (RockShox Maxle) and bearings (6804) directly touches the axle. Front wheel also have 15mm and QR adapters and those adapters just press in the bearing from the sides. And the rear wheel is 12mm through axle like in your drawing.
Regarding sheer forces on MTB suspension forks usually one leg has spring (metal/air) and other leg has damper and both of them are connected with the thin arch which may flex on rough terrain. And in case of inverted suspension forks axle is the only thing that connects both fork legs.
🤯 Really informative. I wish reviewers knew what they were talking about rather than repeating myths and half-truths. Keep up the great videos!
The problem is that with both an Engineering Degree and a reasonable ability to write meaningful sentences with semi correct spelling and grammar, you can get a much higher paying job elsewhere...
7:16 - people mislead by bike industry B.S.???? NO WAY!!! That NEVERRR happens!
Thanks so much for publishing this very informative video. 👍
One place I can see a benefit to a large diameter through axle is in the more extreme MTB application, where the axle is also clamped by pinch bolts on the drop out, which should (I think) increase the rigidity of the fork assembly. Also, the latest axle design on RS forks combines a 15mm axle with a cam action QR lever which should help increase clamping load. Awesome video though, thanks.
Great job explaining and illustrating how this all works. Kind of amazing that a lot of people don't understand how the hubs themself are designed to take the load and the thru-axles just clamp.
Really, there is no "Tech" in Bike, just stuff got adopted from other industrial applications, that have been there for like 30 years plus.
the only true modern tech in bikes now seems to be BS from sales reps. and marketeers. propelled by UA-cam 'influencers' skilled @ changing tires.
It's all about enabling better power transfer. Standard sales nonsense for shoes, pedals, cranks, bbs, bars, hubs, spokes, rims, saddles ...
@@carlosflanders518 and weight, saving 2kg on equipment while the rider could easy lose a good 10kg (talking about myself here).
@@yourrightiamwrong9643 what if you already weigh 55kg? Much lower and it will be even harder to find clothes.
@@imperialspy3457 thats why i am limitting this argument to people like myself. Generally if theres no (healthy) room for improvement in weight or power or position on the bike, then go for dura ace, 1000g wheelset and ee brakes and so on. But we all know that is mostly not the case.
Thanks for the analysis. Repeatable wheel location is the only reason I need to only use Thru axle frames.
Peak Torque, thanks for your content! Having seen lots of your videos debunking marketing claims, I've got a question: what would be your perfect bike from engineering point of view, if it were up to you to design such? Could you make a video on that, please?
Cracking idea!
+1 to this!
Perfect for what, whom, when, and at what cost? Engineering is balancing those questions (and many others) for specific outcomes. there's no one right answer to any engineering problem.
@@davidmarshall2399 "your perfect bike" means what would be PT's dream bike for himself.
@@sepg5084 for what tho? He's shown in his vids he's interested in road, TT and MTB. I'm just trying to highlight the issue with the words 'perfect' and 'engineering' in the same sentence.
I don't think that's case closed. Just done a back of envelope calc and it showed that the thru axle or QR is seeing a higher axial load than the pre tensions you were calculating with your bolt spreadsheet. Once you overcome the pretension the QR will stretch more than the thru axle so in this case the thru axle will make the wheel feel stiffer. With the QR the hub axle end caps will pull away from the inner faces of the dropouts more and allow the wheel to twist.
Weren’t through axles introduced in response to disc brakes pulling wheels out of dropouts? Once you change from a dropout to a hole in the fork end, then the utility of the skewer-type QR is lost: you can’t just drop the wheel out. The through axle simplifies the whole arrangement by making the “skewer” just a single piece of “pipe”.
Thru-axles make a huge difference in resistance to twist. If you've ever ridden a mountain bike with a ~150mm+ QR fork, you absolutely feel the "noodliness" that journos go on about. The extra axial surface from a "thru-axle" makes a difference there...and similarly on rear-sus MTBs, you used see lots of designs where you'd have a four-bar linkage with two disconnected parallel members at the shock which could easily counterrotate, or a train of a million side-loaded bearings to create an esoteric shock curve - there were (and I think still are?) lots of situations where the big 20mm thru-axle formed a proper component of the structure of the frame itself.
On a road bike with proper rear triangles, that factor's pretty moot, but a twist-resisting thru-axle fork is still a good idea. I've a Merlin Inferno, which is a weird Chinesium frame with great geometry, and its thru-axle fork actually has a rubber-bunged hole drilled for a rim brake. You'd have to have a custom hub machined, but think of the sheer stance you could get on the spokes with a full-width pair of flanges on a thru-axle!
Exactly my feelings. Author of video, in all respect to his work, unfortunately analyzed incorrect situation around hub, should around the fork. But the bike designers just wanted to match clamping force of QR with TA. They implemented TA to stiffen fork
@@MsMihalko and rear end also..but yes your right...
My new specialized e bike came with thru axles and boost spacing front and back ! Super stiff and rides great
@@jimbo4203 exactly, this giys far cleverer than i am, but sometimes you look into something so much that you find fault whwn fault simply isnt there
Manufacturers spent millions changing to bolt through, they wouldnt have done all the R&D, redesigned everything, bought new machines to make these things it wasnt making their bikes better..simple fact
I mean technology gets better, F1 cars dont use steel brakes anymore
When's ths last time you rode trails on your road bike? And then put a 150mm thru axle fork on it and rode the same trail and said yeah that's a way stiffer fork!😂
Surely thru axles are about combatting the huge amount of twist torque that discs exert on the interface between the QR/TA and the dropouts? This can pull the axle out of the open end of the dropout, so that is closed and stiffened with thru axels.
Another amazingly informative video - one which I have sent to a number of people who I failed to convince that the skewers offered no part in the mechanical loading (other than clamping).
I still prefer thru "axles" though. They're a little more fiddly for thieves, but mainly because they make it impossible to misalign a wheel. I've seen QR clamped wheels offset numerous times where the owners have not seated the actual axle properly in the dropout. You can't do this with a thru shaft. And whilst a 5mm QR might be able to offer more clamping force, any thru shaft can provide sufficient amount of clamping.
My word...GREAT to hear someone use the crucial lexicon "load path" with facility. My first professional days on the job (1976) I heard a bearded, grizzled vet use that term in dismissing poorly thought out structural reviews.
One advantage of 'through axles' is your wheel doesn't fall off if they come loose. Much prefer the allen bolt type than qr bolts. They may not add stiffness to the interface between the hub and the frame but they seem to improve frame and fork stiffness especially on inverted forks and Horst link frames. I wouldn't want to go back to 9mm qr on an mtb.
Thanks for the education. First was under the impression that the axle provided load bearing and then I upgraded from a QR specific wheel to a 12mm wheel with end caps and realised that was bunk. I was finding that this set up was loosening up by itself over time but I guess I wasn't applying enough clamping force. Was worried I would break it or mess it up if I put too much load on the QR skewer
Analysis from first principles, at least first engineering principles, always provides clarity, big up to you Peak Torque.
What about the fact that in a thru axle interface the dropout is enclosed as opposed to open with qr, would that not limit slippage too resulting in a stiffer interface?
How do quick release and thru axles compare to lateral loading of the fork? I seemed to always get disc rub with an older QR fork I had, but with a thru-axle it's less. Not a good comparison by any means, but I'm still curious of your thoughts on this. Thanks for the content!
How about a standard 15mm end cap hub on a Rockshox fork with the oversize Torque Cap drop outs? When the smaller (standard) end caps are seated into the over size (Torque Cap) drop outs the whole thing flops around until the 15mm thru-axle is located, so in this case, is it fair to say that the axle is taking the vertical loads because the end caps do not mesh in any way with the fork drop outs?
Sure would be nice to see a compression load cell set up to show what kind of clamping forces are actually generated, across TA and QR. Cams are most definitely not all made the same; please consider an appendix with some demonstration, pls? It'd be really nice to have a table of clamping force to brand/model of QR skewer. Those of us with alu endplates would be most appreciative. Also, I've a QR disc frame yet to build and would love to be armed with the facts.
I agree. My Shimano QR's are so much better than my Novatec and SRAM branded ones which sometimes ended up slipping on the dropouts (road riding)
Thank you for a thoughtful and useful analysis. Your point is taken re stiffness of hub but my thought has been similar to other commenters that the TAs improved geometric stiffness of the fork and also but to a lesser degree the rear triangle. I would be very interested in seeing you apply the same orderly presentation format to fork and frame behaviors with the various "axle" types.
I stumbled upon this vid on my quest to replace front and rear hubs on the matched pair of hard tail MTBs that my wife and I have. The MTB market has become so segmented that I don't see anything new that is adequate across the versatile range of riding we do. Certainly see new bikes superior at specific things but we need adequate at everything. Anyhow, all else was spec'd well except the cone bearing hubs. We don't need high end hubs but we do need upgrade to sealed cartridge bearings. Some of our riding encounters contamination that too easily bypasses seals of a cone system. Even when new these hubs had the sounds and friction as if the bearings were river pebbles. If anyone has a recommendation for a cartridge bearing hub set that isn't priced like aircraft parts I'd be very appreciative for the input. Bike is 100 front and 135 rear QR. Rims are 32 hole. Brake disks are 6 bolt. Cassette is 9 speed Shimano/SRAM. Sorry for moving off topic but the community attracted to this vid includes the people I think would have good recommendations.
I see through axles primarily as locating the disk precisely so that the pads don't rub. It would be rubbish if every wheel install required a caliper adjustment. I didn't know about the DT 350. They must have been desperate to save weight at the bearing's expense.
Even with a 12 mm through axle you can insert the wheel at an angle and get disc rub. So the solution is simple and applies both to QRs and thru axles - before tightening the axle, set the bike on the ground to fully engage the dropouts. That way you get very simple repeatability and the same wheel location every time. Which affects not just the (disc) brakes (it will affect rim brakes as well of course, they are just a bit more quiet when rubbing), but your shifting too.
@@Primoz.r exactly. i never understood how exactly people don't have the repeatability of brake location with qr. you just sit the wheel to the ground tyhe rear axle sits on the dropouts and you tighten. this rubbing problem didn't seem to exist befora thru axles came around, so i consider this rubbing old issue, just a marketing hype to sell the new type of product
I have 4 bikes with QR and disc brakes and no issues in locating the wheel for rub free brakes. 2 have front through axles and have had both rattle loose, I have to force tgem so tight I'll need a rock as a hammer to get them loose if I have a puncture that tge tubeless and plugs don't sort. My FS Epic is QR front but has big diameter end caps and this is stiffer than my rigid MTB with a front through axle. Most small developments are just to get you to spend on a new bike.
@@moo4rich I'm no engineer. That's why I kept my opinion to myself. But I kept thinking throughout this discussion why one would not simply place larger diameter end-caps on the quick release skewers. Does that make sense in any way? Were told, don't you dare use quick release frames with disk brakes. Doesn't seem to hold water, that argument.
I really appreciate your effort in your videos
I have got a question. Where do you geht the CAD Models? Do you measure them and build them yourself? Or do you get them from the Web?
Best regards
Ballermän
you should have more views. Finally someone that says everything as they trully are.I myself have found that actually the old threaded axle provide the most clamping force and actually adds rigidity to the frame. Well done.
.....but there is still potential for movement because the dropout is open on a QR system.
Dont mistake clamping force for stiffness of the fork.
Anyway, i love my fox floating axles. Very precise wheel alignment, same clamping force as a QR, and fast removal (approx 5secs). On an MTB they make a lot of sense!
The through axle is designed to make the fork or frame stiffer, regardless of the hub. Greater fork or frame stiffness is transferred to the hub for better tracking of the wheel.
The small axle end area of a qr combined with narrow dropouts and flexible qr allows the hub/fork to flex in relation to one another.
It's not about vertical movement of the mating surface, it's about flexibility.
Apply a side load to a rim and measure deflection.
I’m new to MTB and thought throw axles was the answer, after hearing your examples make sense
Thank you sir
"I pack a big wrench" ... no need to brag! LOL
😂
Thru axle: it is a part that goes through the axle... Misleading name? Not an axle itself but is does describes what the part does... (or am I just being smart now....)
If that's what the name means, then a quick release is also a through axle. But since a quick releases aren't called "through axles", that must not be what the name means.
A number of years ago I was repairing a carbon mtb frame for one of the local jr racers. He had crashed on it and broken a seat stay clean through. When he brought the bike to me with the wheel installed 12X48 Boost the two parts of the seat stay did not line up. When I removed the thru-axle and wheel the two parts lined up perfectly. That told me that the actual thru-axle system had enough beef to it for it to correct any mis-alignment in the drop outs not being parallel to each other. So just another way for the manufacturers to hide their poor quality control.
Overall you are so correct in a larger bolt needing a higher amount of torque to achieve the same clamping force. As well as the axle not being part of the load path. Thank you. I have been preaching all of this for a while now.
30 years ago linkage forks were a thing. The attempted goal being to keep the fork arms parallel and even. The molded crowns on the one piece lowers were getting bigger and bigger but one sided springs made everything sloppy. When thu-axles appeared it was a game changer to add some moment distribution at the lower fork.
Did you know that all modern high end telescoping suspension forks, single crown, double triple crown all have their spring media in one leg and their damping systems in the other? One side trying to always extend and the other side damping slow speed, high speed compression and rebound circuits. 30 years later we have got the sloppy out of single sided springs. And all that is old is new again, crazy huge carbon leading and trailing link forks are trying to come back. www.pinkbike.com/news/structure-cycleworks-linkage-fork-crankworx-whistler-2017.html and now killed by covid19 bikerumor.com/2018/10/25/trust-performance-sends-the-message-brings-linkage-suspension-forks-to-the-forefront/
The next test should be to measure the axle deflection while mounted in an mtb fork. Not sure that it would matter on a rigid fork. I like thru-axle on my road bike because I can put the wheels on when it is in the workstand. Makes me happy every time.
Brilliant mind of engineering. Excellent truth. Thanks
I like TA over QR because I think it does a much better job at holding the disc brake interface in place, so you get much less brake pad/rotor rubbing and scratching, especially when cornering.
I have never noticed any issue when cornering. The only advantage I can see with TA is when reinstalling that it’s bang on each time with alignment
Question: Ti skewers are often said to give a "noodly feeling" and cause more brake rub due to the lower Young's modulus compared to steel, but if there are no signs of slipping in the dropouts, how can this be so? I suspect it's bs but, is it possible that the lower clamping force allows a bit of movement so that the the end-caps are momentarily off parallel with the drop out, but without full blown slippage occuring.
I stopped using a Ti QR skewer on the rear wheel on my bikes and the brake rub is away. Don’t think it’s the titanium’s fault used in the axle but the lack of material/strength in the aluminium end caps (I used PlanetX Ti skewers). I’m able to wobble the rear wheel with my hand after doing them up fairly tight (try it). If so go back to standard manufacturer spec, where there’s a lot more material in the end caps, which spreads the load better and clamping force is stronger.
It doesn’t pose a problem at the front though...
This is a good question. I always assumed it was because of the lower Young's modulus combined with a the higher elastic limit of titanium. Once Young's modulus is exceeded through lateral stress, the rider feels a "noodly" change at the axle, but once the stress is removed (such as straightening out after a hard turn or slowing after a hard sprint) the titanium skewer returns to its original dimensions and the "noodly" feeling goes away. Would be difficult to test in a laboratory setting tho, considering the magnitude of the forces involved.
I use titanium 5mm skewers and have had no issues whatsoever, but they have an Allen end on them, not a QR lever. The titanium hex head is annoying actually because it's softer than steel so I'm always worried about rounding it if I overtighten. Been using them over a year, no problem. I weigh over 85kg and can put out a fair bit of power in a sprint.
@@yonseimatt yeah, you can probably achieve the same clamping force as a steel skewer but the problem would be resisting any additional load in the skewer.
As monsterinyourcloset says it may be difficult to test. A camera fixed on the rear stays for some sprints might reveal something.
Very interesting, in essence then the advantages of TA are more precise alignment and MAYBE some increased frame stiffness due to the precision of the interface which does not rely solely on the clamping force to keep the axle in position. If you forget to tighten your QR things can be pretty dire but even a slightly under tensioned TA will still keep your wheel from falling out.
Hi. Could you please explain how is the clamping torque affected by the Rockshox screw-in + lever "through-axle" system for front forks? The bolt torque itself is quite low as there is only a short lever, but then the lever cam is used to push a wedged element into the "through axle"'s non-disc side interior, and this expands the through-axle and makes a pressure-contact with the non-disc fork leg's "thru-axle hole". I was wondering if this cam system's purpose is only to prevent accidental unscrewing of the "through axle" (which could be possible due to the rather low clamping force attained from the threads due to the short lever) by creating a "friction lock", or if it maybe also provides additional clamping force? I always screw it in quite hard, but the way the rotating lever interfaces with this alu slot in the thru axle suggests that the axle is intended to be screwed in with quite low torque (sort of let's say a few Nm), and then somehow clamped... I guess I could always make an experiment - screw it in so that the wheel has some play and then set the cam up so that it will lock it in place, and see if the play is reduced/gone - but I never tried that yet.
when its described as a "thru axle" its just saying its going thru the axle , not an axle.
QR skewer goes through the axle too.
@@willo7979 yep but they have been called quick release to explain what they do.
@@patthewoodboy So through axles should be called "slow release" then! We have definitely seen a lot of that in road races since they were adopted ;)
I was looking for this comment. Exactly as you say, it's not an axle, it a thing that goes thru the axle and the dropouts
@@willo7979 Right, but that already had a name.
I really love smart people. It is how we all learn and discover and advance. Although in this case I think some cyclists think of stiffness in the fork differently . I understand the vertical force. We get reminded with every bump in the road. I think when some cyclists refer to stiffness it is in the idea of rotational forces. Feeling the fork twist? That wiggle wabble? Sure I understand with load and force and directions but as much as forks and or dropouts skewers, axles and such, how can the twisting feel be improved and will a axle improve strength or resistance in that direction. Should we steer more towards hub upgrade? Especially for the swarm of adventurers strapping loads to the front of forks. Thank you.
Peak Torque, can you make another America's Cup video please? Some good engineering analysis on the Mozzy Sails channel but keen to see another Peak Torque video on their aero packages now the boats have all added new fairings and shrouds.
Through axle doesn’t make the wheel/hub stiffer. It makes the fork stiffer. The chassis flexes less therefore you track better. Axles would bend constantly if they took weight on a mtb it’s only job is to clamp the wheel to the bike. Very good and scientific overview!
You sir are my hero. Subscribed! I have designed automotive beam axles and use joint calculators alot! Just getting more into bikes and was hearing alot of misinformation on thru axles vs QR. I agree with you that they are just a bolt to provide clamp load on the joint and not part of the load path.
Thanks to youtube algo and your yet another cycling myth busting. It saved me from from diving into through axle part. I have RAF 13 front hub. I don't like QR hanging around. What would be the impact on stiffness if I just use small bolts to tighten instead of QR please
Ah the power of placebo. Excellent update and clear description thanks.
Well done, what a great explanation of these two different technologies.
Hey love your videos! Just wondering, is the real axle of thru axle hubs larger in diameter than the axle on a qr? If so why would that not make it stiffer? I'm not personally invested, seeing as I'm sticking to qr either way, I'm just curious. I'm also curious about bolt on axles? Where do they lie in this comparison?
My Koozer XM490 pro QR hub has the same exact axle as the 12mm TA. in most cases the axle on the hub stays the same and only the end caps change
I'm an electrical engineer, not a mechanical engineer, so this was extremely helpful and insightful. Your analysis all makes sense. I had visualized what you have described here as the possible strength dilution but I didn't have the formulae or analysis to prove it to myself, so thank you.
BUT given this awesome analysis, would the forces on wheels, the rigid fork, and the seatpost be unidirectional enough to make the use of carbon fiber in these parts a good place to save weight?
Fascinating explainer, I have questions. Understanding that the end cap/dropout interface needs to be well clamped and accepting that the 4nm clamping force provided by the DT key in the field is going to be far less that of a QR skewer, have manufacturers already factored this in? eg at 4nm hand tight are we getting as stiff as is required, the end cap is not loose in the dropout and will not shift, and it is limited gains beyond this? Secondly, is there any effect on material fatigue, do higher clamping forces tension the forks or rear stays in a different way that may be worth considering?
I'm old school and still use Shimano QR as I believe they give the highest clamping pressures. Always thought thru axles were a con unless they could be tightened enough. Need to carry a FO Snap-On/Park torque wrench in your saddle bag just in case you need to get the wheel out and then refit out on a ride.
I really like watching your videos, you know what you’re talking about 👍.
2 pointers for future experiment/video to mention.1st - the lever in thru axle is quite small to put a lot of torque through it (you mention 4NM), but are the threads in the fork blade really strong enough to take more than 10-15 NM. Perhaps the small lever provided is protecting the threads from being over-tightened by the user and hence shredding the threads and the need to replace the whole fork.
Could you investigate what load would the treads take without damage...
2nd - it’s a fact that many cyclists do their quick release skewers to different tension (some - too loose and some - too tight, that you struggle to even undo the lever) and this affects preload on bearings/end caps/fork etc. differently, but also affects brake pad clearance in a hydraulic disc brakes. I converted my TRP Spyre mechanical disc brakes to BR RS785 hydraulics and I can notice that the pad clearance in hydraulic disc brakes is much much smaller with less adjustability compared to old setup. It’s therefore very sensitive to QR skewer preload tension and repeatability of the same tension...
Hope this makes sense, keep up the good work 👍
I know it is an old comment.
The common misunderstanding of function of QR leads people to false conclusion that amount of tension put in skewer somehow affect alignment of disc brakes. QR is there only to put enough preload to hold the wheel in droupouts by friction, the alignment is done by geometry of fork/frame itslef. Bike manufacturers fucked up the concept and made the surface of vertical faces of droupouts and/or hubs serrated. They've probably thought it is a good way to add extra friction into equation. However, this cause misalignment everytime you dismount and mount your wheel because you are unable to hit the previous configuration of dents.
Glorious to have somebody doing videos like these
Incredible. I love this video thanks so much. Can I ask, why do you think thru axles are more popular with major brands? Is it actually just more safe because it cant fall out of the drop outs? (Like if you are stupid enough to not tighten your qr and do a jump).
Great video!
One comment on the cross section of the rear hub: this is NOT like DT designed their 240. In my opinion it is for a 240 like so: the axial clamping force there is transfered from (right to left):
- right endcap
- inner race of 1st freehub bearing
- spacer ring between the freehub bearings
- inner race of 2nd freehub bearing
- another spacer ring inner race of right hub bearing
- right shoulder of hub axle (so no play there)
- left shoulder of hub axle
- inner race of left hub bearing
- left endcap.
There is a gap between the endcaps and the face sides of the hub axle.
Thanks for the video! But could you explain why the same 4nm torque on the M5 QR generates twice the clamping force as the M12 thru-axle? That seems very counter-intuitive.
Probably thread pitch / angle differences.
The 4Nm torque that PT refers to, should be QR lever torque, not a screw tightening torque.
This torque on QR, is taking advantage of a cam in the QR, ramping the axial pull on skewer up many folds hence the clamping force.
But I believe PT is using the same calculation as M12.
For M12 Thru Axle, it is a direct screw torque, hence you really need to tighten it as per suggested by manufacturer to achieve the same and desired clamping force.
However, it's a broken system for many niche and unreliable manufacturers, because they either they don't know what they are doing, or they are closing one eye, or both.
@@willo7979 Thanks. I was wondering about that. When I re-played the part where he did the calculation, the only thing he changed was the screw diameter. I don't recall him making any other calculation changes. But I can see what you wrote is the only plausible explanation.
There'rs been QR Axles with disc brakes! Thru-axles wasn't invented because of discbrakes!
Yes, but with QRs you can have the wheel pull itself out of the drop-outs, if you're unlucky and lock up the brakes (at least on the front), so I'd still say Thru-axles are probably the better choice in that respect.
@@dalailambda9420 unless it's a shitty dropout it's very unlikely to happen. Most of the dropouts for disc brakes with qr have little flanges around the area where the skewer cap goes. Simply said: thats not just flat thing with cutout on the bottom. So even of it's not tight enough the wheel cannot be pulled out. Most of the cases - those flanges are too small (shitty fork/ frame) or non existing (even worse manufacturer or some improper conversion to disc brakes) - or (worst case) somebody didn't check if the skewer are clamped properly.
@@dalailambda9420 Nope, not if you install it right and tight. It's going nowhere. Not with lawyer lips on the fork. It's simply impossible.
The main problem with QRs not clamping wheels strongly enough, is that so many people don't know how to tighten them properly, in the way they were meant to.
@@dalailambda9420 have you ever seen a qr wheel pop off place cause of disk brakes? I my self haven't seen this, like ever.
Really interesting. Warmed the heart of this retrogrouch.
Very informative. How about the Mavic Speed release axles? Do they clamp tight enough?
If you do them up to the recommended 10Nm then yep. If you get the ones with the built in lever, the lever clicks round once you hit 10Nm, it’s effectively a built in torque wrench. Clever design.
I tend to agree with the theory that a thru axle , and the bracing needed now on the front fork due to needing a stronger fork mount for the force placed on that area by the braking calipers in that area , has now removed the natural springing in the front fork which really has a lot to do with ride comfort. My vintage Raleigh Super Course had an amazing ride. I gave it away and now recently bought a vintage Raleigh Super Course MK ll with beautiful curved fork. I am servicing all the hubs, crank, head set and looking forward to the ride. The bike industry is just to geared towards changing things right now.
Really make sense M12 decreases the force amplification of the built-in clamp lever compared to M5 to get the desired or max torque. Thank you for sharing your technical knowledge. Great content!
So what would be the ideal solution? Here's my suggestion: 5mm solid thru axle. You get the increased clamping force and repeatability of locating the rotor, with a more easily manufacturable skewer - people could even use their old skewers. Suspect easier to align the frame during manufacturing. Would love to see a follow up also talking about fork stiffness -- the fact that lefty forks exist suggests to me that the thru axle doesn't do much here.
What would be the point of using a qr as a TA? 🤔And why would anyone ever want to use their ancient qr skewers on a brand-new bike? 😂 That makes no sense whatsoever, as it’s the frame and forks which determines if a TA is used. 🤪Moreover, I very much doubt a 5mm TA will have sufficient ability to locate the wheel and disc as there’s just too much play in the threads themselves when they’re such a small diameter.😱
The stiffness that I found with a 12mm bolt vs the qr was actually in rear triangle flex. It’s harder to twist the rear triangle then previously. That was the stiffness I was after.
Basically you are calculating just the side to side load on the axle not the whole bike. While I agree you are right when only keeping the axle/wheel loads in mind overall frame the smaller diameter doesn’t seem to provide as much. I don’t know I felt it did more in the department of changing how the rear triangle behaved because the larger diameter prevented frame flex to a degree. The same goes for the forks as well. The “thru axle” is more for connecting the legs then making the tire stiffer.
Thanks for that video, made me understand the engineering of hubs and "axles"
This video completely missed the frame/fork interface and how a fork with a 10-20mm overlap of the axle will be stiffer than compressing a slotted dropout between the at head and the axle. There is a clever caveat at the end “ not stiff in the way most people think they are” so the actual subject of thru-axles benefits can be ignored
What exactly do you mean when you say a “10-20mm overlap of the axle”? 🤔Exactly which part of the fork is different from currently and what is overlapping what and where? Also, the only person who’s ignoring the benefits of TAs is you. 🤨This video is NOT about the benefits of said axles, it’s whether a TA is stiffer than a qr, which as we’ve seen, it isn’t, in the vast majority of cases. 😳The only thing which has been completely missed is your understanding of what this video is about. 😱It definitely didn’t miss out on anything.🤓
Great material. I always wondered why hub companies do not use the TA as the real axle and put bigger bearings (12mm ID instead of 15mm ID) as the hub axle and TA seem redundant and I did not know DT actually had one hub designed like that. But you are right about the fact that doing it that way you need a very sloppy fit to be able to remove the wheels in the field... Now, I fear that we may see plastic bushings like in the Shimano BB making their way into hubs (or hopefully the Mavic experience with plastic bushings in freehubs was painful enough...)
I have a flush (no lever) 12mm Thru axle on my Cannondale that has a 9 ~ 13.5Nm rating. I used a torque wrench and torqued it down to 11Nm.
congratulations, You have the same clamping force as me on my shitty QR's
@OmegaMan I have strong hands, anything up to 20Nm is doable with a short allen key. It will leave a nice red tattoo on your handpalm for sure ;)
And you can always lean down with your shoe on the allen key...
I thought, like a motorcycle axle, the idea with a bike through-axel is that it's a very tight fit in the dropouts. Such a close tolerance that no slippage is possible and therefore much less clamping force is necessary. The idea being that it's an axel system that does not rely exclusively on friction resulting from high clamping force to maintain axel position in the dropouts and wheel position.
If that's not how they work, guess what kind of modification I would make first?
The term stiffness comparison of thru vs qr based on clamping force comparison is selective analysis. The diameter of thru axel hubs vs diameter of qr hub caps against the fork is more relevant. Though contact surfaces of hub cap against mating parts is far more significant for fork, versus the rear dropout. Hence caad qr rear.
My super X dale is qr rear, no where near as stiff as my road bike which is bolt through....
Friction does not depend on surface area. F=mu.R
You can look it up!
Who mentioned friction? Surface area. Torque Caps, for example. Bracing angles? And why are you calling them thru-axles when it’s a bolt through, let’s not perpetuate a myth.
@Pablo Morales qr bikes always have paint chipping off the dropouts... bolt through doesnt....
Amount of times ive had to removed deformed paint from qr dropouts...never had to with BT
@Pablo Morales My QR bikes does have some carbon or metal eaten in the dropouts. not to the point of failure but it has some because there's high pressure in this points.
The pressure is more distributed in the case of a thru-axle.
I’m pretty sure the thru axle was never meant to add wheel stiffness or vertical stiffness. It reduces compliance when leaned over as it helps to maintain the 90 angle between axle and fork leg. Basically preventing it from going parallelogram. As the loads on a MTB are often off center because the tire is wider, these side loads are more common and the thru axle is more important. Road bikes become more responsive when really pumping As you’re not twisting the fork.
It took me almost a decade to jump on the thru axle bandwagon in MTB. Going from a dirt jump qr fork (massive crown) to enduro thru axle forks I could not tell the difference. I'm thinking what people were actually feeling were wheel and fork design changes.
Ive had 2 sets of the same wheels 1 was qr one was bolt through
BT was far more rigid
Forks were the same (qr version amd BT version)
BT feels noticeably superior, if you cant tell the difference there is something wrong....
Next people will be saying running a 23mm tire and a 28mm tire feel the same
@@karl8805 While thinking it's the wheel that makes the diff. Have you ever thought that that the fork end on your BT fork is forming a close loop (compared to a QR fork) and that should be given some credit too, if not completely?
@@willo7979 my point wasnt the wheels, it was the BT set up as a whole was far better
Thank you. I always had this suspicion, but never had the knowledge to prove it. Never felt any difference to qr, in fact when I was a bike messenger I had really low atc fork, the 22mm tires the bike came with just barely cleared at the top, soon I had to change tires and I could only get 23s, so I had to lift up the bike a bit before clamping down the qr, so the axle wasn't all the way in the dropout. And I rode like that for months thru cobble stones, endless potholes, speedbumps, jumping up and down curbs, drafting behind buses, doing 90-100 km a day and it didn't move once.
Most normal people wouldnt be able to tell the difference....i can
Same with these idiots that say 105 feels the same as ultegra when it clearly doesnt
What about the argument that through axles unify the dropouts to create a stiffer construct inside of which the wheel lives?
Exactly right. He just glosses over this. I don't think anyone has been saying the wheel itself would be any stiffer?
I think that’s what the clamping is that he’s talking about. The problem is how to get it tight enough. The DT Swiss lever he mentions doesn’t have enough leverage.
@@johnegregg I don't think that's what he's referring to. I think what he's talking about is the ability to create a good interface between one side of the dropout and the hub flange. Not about attempting to unify the dropouts into a single construct. Because with what he's talking about, the QR accomplishes it more effectively to and I'm going to have a really hard time reasoning that a QR more effectively unifies one dropout to the other. Maybe the reason that thru axles can get away with shorter levers is that they don't need to be as tight as QR's to accomplish what I'm talking about as effectively.
I quite like the Suntour quick lock thing, it's essentially a QR Skewer in the form of a thru axle
I think you misinterpreted the fact that a thru axle provides less clamping force: that means it's stiffer so less force is required, as some have said, it's an extension of the frame and adds structural integrity, keep in mind that it sits flush inside the real axle, with no play, and it remains locked with it.
Great explanation! Any idea what torque setting pro mechanics use on their impact drivers for road disc wheel T-As?
I imagine they’ll use the same regardless of whether they’re on the road or in the service course
Totally agree about the load path and how the thru axle doesn't add anything to the stiffness really. But there's something odd about the bolt calculation: why would a larger bolt give a lower clamping force with the same torque?
Does thru axle maybe provide more stiffness in the fork itself as it is screwed into the fork and not just clamping? could that be some stiffness people relate to?
I'd contend that the actual axle on the DT 350 front is a combination of the center sleeve, bearing inner races, and end caps. All are held in position by surface friction and the thru axle still doesn't necessarily contact the bearing or all other parts.
That's the point.
@@Gyikhuszar88 video suggests that this design places shear loads on the thru axle. My description suggests it does not.
@@n0ch91c3s I agree with you. However this sounds a little bit strange. Something should wear the loads come from the front wheel, I think that friction between the edges of the spacers - bearing inner races - inner spacer - sleeve would be not enough.
A thing I'd like to see addressed though is the stiffness of a suspension fork with 5mm vs 15mm. Surely it's the larger clamping surface diameter you get with a bigger thru bolt that contributes to the stiffness? I'm sure I'm not explaining it very well, but when Marzocchi made their first USD fork (Shiver, IIRC?) they specced a large diameter thru bolt, I think 20mm, because anything smaller made it feel noodly. I guess it makes little difference with the rear dropouts as they're one corner of a triangle anyway so not subject to moving away from each other they way that the more independent legs of a fork are.
Torque caps (the sram standard for MTB) I think “proves” this as well. I imagine the larger surface area of the torque cap helps increase stiffness by making it harder to rock (due to the larger supported diameter). What are your thoughts on torque caps?
However I always thought the QR partially relied on the nipple of the end cap sitting in the dropout. Typically when installing the hub in the frame/fork I would make sure these “nipples” were bottomed out on the dropout before tightening the QR. thus the typical vertical-ish loads can be taken by the normal, and the friction. That’s why QRs can be ridden with the QRs being pretty loose. Which is probably one of the things that has lead to the lawsuits and thus the death of qr.
"Lawyer tabs" yes, are there to prevent the wheel falling out in case where the QR is loose. QR's are not going away because they are unsafe, but because the manufacturers and marketing folks are brainwashing us to buy something different.
Next do Flat Mount vs Post Mount comparison. Would like to know how much the mount style affects torque and alignment under load
Isn't the main selling point aero gains.
My brother went to a bike park a few months back. He had a blast ripping his side knobs off his tyres. As he went back home he realized, that his draw bolt came lose. He replaced it afterwards.
With a lose QR he probably (almost certainly) would have lost his wheel, and would have been seriously injured.
The main benefit to through axles is that you can not lose them so easily and the disc-caliper alignment is really good.
Excellent. Learned something counterintuitive.
Hi I’m using GRX wheelset, how much should I tighten for rear and front? Is a cup cone bearing, front 12x100 & rear 12x142. Thank you
I do own a Chris King hub(disc) R45. So on the rear hub I struggled to find the right torque necessary to make the end cub to the Hub axle. If you leave it to loose it will leave the wheel with a wobbly effect (regardless of the torq applied on T. Axle).
But I notice if you apply ther force necessary to not have the wobbly it take quiet a lot of torque but then I feel the bearings being squashed to the point I can turn the cassette in the opposite side just turning the wheel axle with my fingers. For some reason I find this very poor design. Hopefully I am wrong here.
Correct me if I am wrong. Is it not better rely on QR or TA torq force on the end caps rather than have two different sistem applying force in the bearings!?.doesn’t affect the performance of the bearings!?
Nice, thank you. My 15mm front is a QR through axle and now seeing this I’m glad I have this set up
My 2013 Devinci has a rear through axle but its just a longer skewer. Same diameter as qr.
Your joint calculator assumes solid cross section and material properties. Question: Having never built a bike, are thru axle bolts and QR bolts a solid cross section or hollow? And is the material similar to grade 8.8? Just want to make sure.