Don't know if you read my commentary on the last brake gmbn video, but I explained how brake rotor size has nothing to do with braking power- as far as bigger = more power. A brake rotor in essence is like a heat sink. Surface Friction creates heat which is then absorbed and dissipates heat, converting kinetic energy to thermal energy. What a bigger rotor will do is stave off brake fade more efficiently than a smaller rotor. Thermal conductivity is the goal. You want pads that can absorb and dissipate the proper amount of heat from the friction to the rotor and still be within an operating range that will optimize braking power. Once the pads have surpassed their efficiency operating temperature they will begin to glaze from overheating and no longer be able to transfer the heat energy to the rotor and vice versa. If the rotor becomes overheated the pads will absorb excess heat from the rotor as well as heat from the applied forces of friction. And the result is that the friction coefficient will diminish- I.E.- brake fade
Once the tyres lock up you are still testing the brakes in real conditions. The back wheel can still jack on trail, especially on a full sus, if the brakes are poor they may not remain locked, also you will modulate to just before the lock up, better modulation and power means your hands won't get as fatigued on longer descents.
A couple of other things to consider here are brake pad composition and how that relates to the rotor temperature ramp up. Disc brakes need some temperature to function and that temperature is dependent on pad material; resin vs. sintered. The stopping distance test showed that the rear just locks at the pad "bite point", where the pad makes initial grip, and the 220mm rotor took longer to heat and provide the needed stopping power to slow down then the 200mm. The bite point is different between pad materials as is how quickly they heat the rotor up. If you watch most types of car racing you will notice that the teams change the brake duct sizes to keep their rotor temps in the optimum range. Formula 1 is a good example. If the driver lets the brakes get too cool, they are useless. What it all comes down to is experimenting to find the best combination of pad material and rotor size that works for the rider and their terrain. On my hardtail with 2 piston calipers and sintered pads I never felt I needed bigger then a 180/160 front & rear.
Formula 1 brakes are carbon rotors and are designed to operate at high temperatures. Bike brakes are designed with normal riding conditions in mind and will be operational at cooler temperatures. They may not be optimal. The same reason normal car's brakes are metal rotors; they need to work straight away.
@@lenolenoleno can't imagine being so lame you have time to comment on a 5 month old reply. No wonder you have time to read that novel, you have nothing else to do it seems
I have the same Shimano MT6100 breaks on my Trek Roscoe with 200mm front and 180mm rear rotors. I also noticed an improvement in breaking and feel from the stock MT200’s and 180mm front rotor it came with. I dont do any downhill trails so this setup works very well for me and didn’t break the bank upgrading. Thanks for the video! 🙏
Interesting video. Definitely do a part two with a longer test track. Also add in a heat dissipation time. Like heat of rotor right after then another minute after to see how much heat it lost.
Lean back when braking. Also. I've seen tests that were done multiple times in each of your categories and the ones that responded better, was after the first initial braking. As if heating them up at a certain point seems more effective. Excellent job yes
My Trek Fuel EX has 203/180 with TRP 4 piston calipers and they’re perfect for me but when my wife who’s 100 lbs lighter than me rode my bike she hated the brakes because it was so difficult for her to modulate them. She much prefers the Shimano MT200 180/160 on her Polygon Siskiu D7 that feel like mush to me…it’s all very personal.
On my 2015 trek Remedy 7, the stock parts were Shimano deore 2 piston; 180/160 rotors. When I raced and the descent was greater than 5 minutes, I had brake Fad ( big loss of power). I switched to 203/180 seven years ago and have not had one moment of power loss or fad inside and outside of racing!
As heat builds up in the rotors and pads the "capacity" of the brake system gets filled up and tires get more and more prone to locking up as the energy finds it easier to skid the tires than to turn kinetic energy into heat where there's already a lot of heat built up. I like to think of the rotors as pools in which I can dump my kinetic energy as heat. The rotor size is the volume of the pool, the heat dissipation is the sink of the pool. The bigger the sink the faster it drains (duh.) and the larger the volume the more speed I can dump into it at once. It is surprising how many riders are willing to let go of that braking performance for the measly gain of a few grams. Better braking means higher overall speed through confidence, control and safety. Tire grippiness is what determines how full the pool can get before I start skidding which is to be avoided if we want efficient braking. Just my 2c.
I think for lighter riders like her 220mm doesn't make any sense. As she noticed, they lock up on her too quickly especially in the rear and thus reduce braking efficiency. For me personally a 220mm in the front is the way to go on my Enduro bike, but I'm also quite a bit bigger and heavier than she is. So essentially 220s do for me what 200s do for her her.
7:12 "perhaps the 220's where too powerful, we skidded" that is what happened. Once the wheels lockup the tires are no longer able to extract its maximum grip/braking capabilities. 180mm had no skid. 200mm skidded just a bit. 220mm skidded too much to stop maximally. The larger rotors also have a higher thermal capacity and thus requires higher temps to be optimal. Just as the video concluded, the bigger the rotor the higher loads are required to get the most benefit(heavier rider and/or DH applications)
My trails are very short descents and punchy climbs. I could be entirely wrong but I've found that a 160 on the rear spins up heat faster and grabs a lil harder for me in the short braking spurts i deal with at my local trails. I think on a long decent I'd melt it and fly into the trees though. (I'm a wheel bending 285lbs) Something to think about if your descents aren't long at your local trails!
You are correct a smaller rotor will heat up quicker thereby transferring the kinetic heat energy into thermal energy into the pads. For a short period of time a smaller rotor will be more efficient but on any sort of prolonged usage the smaller rotor will no longer be thermally efficient
You should try to descend Khardungla in Ladakh. It's a 5300 m mountain pass which descends to 3500 m on a distance of 40 km. A full hour of descending. Riding it up is a good training
Drag test would be a good test. Your trail test, yes make it longer, but also do different trails one being a fast flow trail and the other being a slower tech trail.
I'm pretty sure they did but, just in case, were the rotors bedded in properly? That can dramatically affect the performance of the brakes. Also, it would be nice if you could mark the braking point and not only the stopping point. Maybe you did Mark it but it wasn't told in the video. Finally, don't take your foot out of the pedal before the stop has been completed, Anna! That can affect the result as well. Maybe go flat next time, so that you can focus on the braking only. Just a few suggestions. Love it, guys. Keep'em coming and go Anna!
I think drag brake test on a down hill will be more realistic for the bigger rotor. Great test anyway to show but replacing the rotor itself can really change the entire dynamic of the stopping power & feel.
I've got 3 different bikes with 3 different brake discs, and I never felt like I didn't have enough brakes. I haven't ridden my new Pivot Switchblade yet, but it's got the biggest brakes of the three with 203mm in front and a 180mm rear, but with 4 piston STX calipers front and back. I'm sure the braking will be ruthless. I have no desire to change rotors on any of them. The front brake is supposed to be doing like 70% of the power, you definitely seem to favor your back brake. I've had quite a few motorcycles, and the last one I owned had dual 320mm rotors up front with 4 piston Brembo calipers on it, and just a single 220mm rotor in back with a two-piston caliper because the front is where the power comes from. During the panic stop testing, you could have used the front brake harder instead of locking up the rear and dragging the tire. I know in the loose stuff you're worried about losing the front end, but there's more front squeeze to be had IMO. ;)
Size makes such a difference I remember way back when I saw one of the bigger boys light a fag/cig off his160mm hope mini after his lighter died then years later a rider who was also there found 180mm just didn't get hot enough to pull off the tame trick
Stay tuned for the next videos within the series "is physics even real?" featuring bangers such as "does gravity affect descending?" and "will more suspension travel result in more suspension travel?"
I would think that your idea of science doesn't match this video. Larger rotor size does in fact affect braking performance. It all depends on how you ride and your equipment.
No matter the size I keep warping rotors. But some reasons for that can be sticky pistons, so lube the pistons. Rebuild caliper with new seals if needed. Only do that hwen they leak and get stuck even with lubing. I gone side is sticking there will be a bad brake feel and pad will have a gap between the rotor. And other sid eiwll bend the rotor. But even with perfectly working brakes I keep bending rotors. I run 223mm rotors front and rear. In warp rotors less with bigger rotors but still do it. I ran 180mm rear, 203mm front Hope Tech floating rotors. Now I run 223mm Trickstuff rotors. I opted for rotor with no rivets for no creaking, got them second hand offered to me for half of retail so had to try it. Hope floating rotors defenitly perform much better than resin only rotors in same size, I've had 160 rear 180 front on my previous bike. So massive upgrade. But after years of use it creaked in the rivets.
I would take this test with a very large grain of salt, braking performance on dirt is almost always limited by grip, not by how big your rotors are, I've gone from 200mm down to 180mm and my braking performance hasn't changed, the only thing that has changed is the smaller disc requires slightly more squeeze from the lever on very steep descents, maybe the issue is the weak 2 piston calipers? they probably can't get away with running a 180mm rotor.
I have two similarly equiped bikes, but one is a hardtail, the other a fullsus. Both have 203 up front. The fullsus also has a 203 rear I kept the rear down to 180. One of the hardtails biggest drawbacks is braking on lose, chattery terrain because the rear starts to bounce and skid. I feel a larger rear rotor would make it skid more.
I agree... You could try harder pads to decrease grip to the rear... I still think that rear brakes are overrated and you can be a better rider the less you can force yourself to use them.. but that comes from years of motorbike riding where onroad rear brakes are actually dangerous (a lot of racers make them near useless so they don't accidently use them in a race) and on the trailbikes I became faster on my old bike when the drum rear failed and I learnt how to brake hard upto a corner and no brakes through it (to the point where I was entering corners with the rear in the air (which is why I say rear brakes are useless (Except for stopping at slow speeds like lights.
Thanks for the video, Stop distance, heat & times are always going to be 'rubbery', you'd have to go a brake dyno & thermal camera, FEEL - or modulation - i think is key, the harder you have to squeeze - the less FEEL, so go bigger Also you taught us we need to bed-in the rotors with pad material??
Upgraded my Slash 8 180/200 to 200/220 after my brakes were overheating on longer runs. 10 minutes plus. Made a huge difference, with no overheating. I also like the sensitive braking, which some people may not like.
Sounds spot on! You can always switch to a braking system like Srams where the modulation is far greater giving a less sensitive lever feel, but easier to modulate power.
The distance test is subject to far too many variables such as initial speed, surface temp and modulation of the brake and as such can be misleading, to understand which brake produces the most braking you need to do a G force test with a G meter and do multiple runs to produce a bell curve, this way you get a clearer picture of the brakes performance. the braking limit of the bike is not the brake disc and caliper but the coefficient of friction of the tyre to surface, a small brake can lock up on mud for instance. you also have to factor in the weight of the rider bike combination, a 60kg rider on the same weight bike as a 100kg rider produces vastly less kinetic energy at the same speed, so to produce the same G rating under braking a heavier rider will require a larger brake. Some riders will prefer a more sensitive brake lever that is lighter to modulate and control, that lends itself to a bigger brake whereas other prefer a brake they can grab without lock up, opposite requirements. Then we get into the kinetic issues such as weight transfer, a taller rider will have a higher center of gravity than a shorter rider and therfore transfer more weight to the front wheel under braking requiring a larger brake, all of which is subject to our initial starting point of the coefficient of the tyre, which as mentioned earlier is the limiting factor. suffice to say you have to tailor your brake sizing to your own requirements, the only given factor is, due to weight transfer to the front you can reliably use a smaller disc at the rear to control lock up as weight and therefore friction is reduced by weight transfer under heavy braking. On my own bike I use a 203mm disc and 4pot caliper on the front and a 160mm with 2pot on the rear, this is because I am 6ft 2" tall and weigh 105kg,
I've put a bigger rotor on the front and a smaller one on the rear than the stock setup. There was too much power on the rear for the amount of grip that wheel has, making it hard to modulate to the point of lock up. I suspect bikes coming with too much rear braking power is why we have so many braking bumps at trail centres!
Horses for courses. On my enduro bike I'm happy with 203mm front and 180mm rear. Tried 203mm rear with a four piston Zee and it was actually too much brake for me on pretty steep trails. Finger rest on the lever in the air would start locking up the rear and then dip your nose on jumps. Combination of quality caliper and adequate rotor size makes more sense than just upspeccing rotors. On DH bikes, or enduro racing, then by all means, 203 or 220 makes sense, but I think there is a thing like too much brake for purpose.
I don't think brake size would help in this test other than lever effort. The main advantage of big rotors is their ability to absorb and dissipate heat in multiple stops
There is no change in lever effort at all because that would mean you'd have to change the ratio in the master cylinder as it pushes the hydraulic fluid through the caliper into the Pistons. It's a fallacy. It's simply psychological perception
@@rider65 A bigger diameter rotor is moving faster through the caliper (or has more leverage on the hub). Therefore, you need to squeeze the lever less for the same level of braking force.
Next time avoid locking the rear tire specially on asphalt, that situation show that brake balance is not well performed and modulation is not executed properly. Removing those mistakes will provide more accurate results
I would love to see a drag brake test, especiallyon the rear. Get it up tp speed in a controlled Environment and drag the same distance. Maybe also how quick the rotor is cooling down in 15, 30 seconds.
Nothing was noted about tire grip. Your tires have a lot to do with how effective your braking is. GALFER makes a 243mm rotor. Overkill unless you're doing a bomb run down Pikes Peak. IMO, 220/203 is a good combo for aggressive enduro/DH riding for riders over 180lbs. Why would anyone gage their bike performance on EWS or XC racers. It's all about feel and performance on the trail.
I used to think always bigger the better but I came back to 203 up front and 180 rear for optimal balance of raw power. That would be a fun test, playing with size combinations like 160 up front 220 rear! Drift machine?
If you really want to get an idea of heating and cooling, The Bike Sauce channel put a data logger on his disc and did testing on a road for consistent, hard braking. I've been meaning to repeat this to compare Ice Tech to cheap rotors... Heat dissipation rate. 50C is nothing to be excited about. Heck, sometimes the ambient temperature is 38C. I've measured 100C without fade. Pretty sure pads and oil are rated well above that.
If you temper stainless steel it gets different colours. It gets the same colours if it heats up at braking. If parts of the disc reach 200° they get yellow, if they get blue they are more near 300 °. My disc rotors are yellow beside the braking surface.
Love you anna.just had a s-works epic ht built for me,and these are always 160,mm rotors with xt brakes,find myseld doing a traffic copper running commentry,stop stop stop,this has made me think.maybe look to go to 180 mm front and rear,bit surely brake compounds play a part too❤
@GMBNtech..... Hi guys. at 12.09 caption said "REAR DIC BRAKE" (220mm rotors) ???? Wasn't this proofread before posting? Was this overlooked? It's the first time that this happened!
@gmbntech could we hear a little more about the hardtail you were using for the test, I noticed you didn’t have a fox or rockshox fork. Great job Anna as always!
as @floydblandston108 said - while braking you didn't really change the way you modulate (or did not modulate at all) nor your body position. There was very little gain in braking if you don't actually use the grip of tires. I was surprised that you didn't pay attention to that more, you know better! :) Braking distance should be measured ONLY if you did not skid. also forth mentioning that not all discs have same surface and is not acting same with all types of pads + include the 'bed in' period required and etc... there are quite a few variables, but for the purpose of this video - the point was made! :) Very interesting video anyway! I am happy with my Magura MT5 with 203 up front
Realistically, you can lock your wheels with either size, so the braking power is there in all cases and it's limited by traction, i.e. tyre/terrain combo. The size difference matters technically only as far as heat management is concerned. Dissipation is a function of surface area and one can easily have a minimalistic 203mm rotor with less surface than a bulky 180mm rotor. Regarding heat accumulation, a bigger rotor will always have more braking surface (larger circumference that comes in contact with the braking pads), so it should heat up slower than a smaller rotor. Larger rotors provide different feel due to modulation, which isn't really bike (or rotor) performance, but rather rider performance. Note that in all cases the contact surface is the same since it's determined by the pads' size, so the difference in modulation is only due to the radius, i.e. you are playing with leverage - that's literally like changing the length of your brake levers.
The main reason for bigger discs is for higher speed tracks,DH types & heavy bikes & riders....eg; e-mtb's ..I'm 78kgs on a 25kg e-mtb so 223mm front & rear give me a lot more control.....steering & braking.
You need to do this on a full suspension bike for real reaults to compare to why enduro racers use 220mm rotors. Hand farigue, especially with basic brakes makes a big difference on longer runs too.
I run 180 Ice Techs on both my Trail and AM bike with the AM bike getting 4 piston calipers. I've tried a 203 in front on the AM bike and not a huge difference for me.
If you are a heavier rider, like 85/90 kilos and more and you ride steep and long tracks bigger is better, I changed from 200mm center line in the front to 220 hs2 rotor, I don't feel much more braking power, but there is a difference, and a thicker rotor is a good thing too 🙂
Would be smart to mention, that the 220mm rotors for YOU were inconclusive compared to the 203mm ones. I say for YOU, because you weigh (let's say) 50kgs, but for a 100kg rider, a 220mm rotor may be even less "powerful" as the 203mm for you. Also you (pretty nicely nailed) mentioned the grip of the wheels (tires) that you need for those bigger rotors to "shine". On tarmac, with that knobby tires you have everything, but grip. And the last one: you compared some "bedded in" discs to some brand new ones. The brake pads needs to "wear together" with the discs, which needs a bit more time (miles) to offer the maximum of their potential. Ultimately: the "heat check" was also inconsistent. If you're curious about that, you should not ride them on a trail, then you measure 'em yourself, hopping down from the bike. For this test should be more accurate a longer and steep descent (for even more consistency a paved road), where you brake your bike to a certain speed, and maintain that speed (for example 25 km/h) from top to bottom. Then someone should wait for you with a switched on heat measurement tool at the "finish line", for immediate "reading". As you've noticed, these rotors cools down pretty quickly, so every second counts. Recommendation for a future, even more accurate test: be more constant in measurements, speeds, disc/brake pad conditions, and you could involve (at least) 2 more riders (a 75kg, and a 100kg one) for demonstrate which rotor is the best for your audience. Cheers! PS: switching from a 203mm rotor to a 220mm one is a 8.78% increase of braking surface area (you have to calculate the contact surface with a brae pad, not just a line -> circumference of a circle). And yes, I said 203mm, because Shimano SLX rotors are available in 160, 180, 203, and 220mm variants. There's no 200mm option.
#askgmbntech Can 4 piston calipers be used with Acera levers? The nut on the valve stem to tighten it to the rim are instructed to only finger tighten, but what happens if you can't get a seal. I noticed that Problem Solvers has a wing nut looking nut to put more tourq on the nut. Why would this be any different then carefully using plyers to tighten the nut
Thanks Anna, good info. I'm trying to get into doing my own bike work. If i upgrade my 180 rear to 200 to match the front is anything more required than just bolting it on?
It depends if your frame uses post-mount or flat-mount brakes (Different bolt distances), you would need a specific adapter depending on the mount type and rotor.
If your not getting the pads up in temp due to excessive power for the riders weight, style, tire grip and speed then they wont perform as well as say a 180mm.
So, here's a quick tip - not always need to Size Up in rotor diameter - try just getting one of the ticker ones, same size. I changed from 200mm diametr SRAM Centreline - 1.85mm thick to SRAM HS2 2mm thickness - same pistons and callipers - massive stopping power differnce. You don't always need to go larger diameter - so no extra adapter needed either. simples. 🙂
I like my rotors big, but keeping them true, clean, and non-mooing becomes harder with size. A set of 160's run hot with grippy pads wears out faster, but every metric but maximal braking power is more enjoyable. Brakes *like* some heat...
Old car guy here....if you are going to track day your car, the first thing you did was mount the biggest brakes you could fit on the car. my e bike and my mountain bike both have 220 rotors.
I love you guys, but I rly miss the more science based approach where you take out variables. Anna is only human so how about we equip the bike with abs, do every test indoors, on clean tarmac, same weight distribution etc. Thn maybe we can see exactly where a bigger disc is making the biggest difference aside from finger feel. I'm a super lightweight rider that just uses cheap shimano mt400 stuff on 160mm discs and I haven't encountered a situation where I needed more braking power (in the Netherlands) but I also have higher than average grip strength...the strength that can pull v-brake cables out (happened a few times) and it's personally a big reason to go for hydraulics, the extra modulation is also rly nice..but yes, I never experienced high end brakes and I can heat up a disc in about 30 seconds to the point it might burn you when touching
I love this channel very much, however this test is unfortunately inaccurate considering the rear tyre was sliding almost the full duration of each brake test, the idea of testing rotors is not to see if it will lock up the wheels but to see how quickly they will take you from whatever speed down to zero with the least amount of wheel lock up possible. With proper braking technique you should be able to apply just enough brake force on each wheel to just where the wheel is about to lock up but never actually does to give you maximum braking force with each lever pull.
You were clearly locking up the rear with 220 whereas the 200 was acting like ABS during emergency braking. Didn't look like you locked the front at any time and could use more power there. A wet test would be good to see how easy you can modulate the front without locking it up.
I can feel engineer and technicians crying at the use of the term science 😂 I run what my LBS Sensei mechanic suggests. FYI I run 220 F&R on my e-bike, 203 F&R on my enduro and 180 on DJ bike. I’m 6’5”, 96kgs 🤘❤️🌈🕊️🌎
No they don't. Why would a larger rotor affect or change the ratio of the hydraulic fluid in the master cylinder and the Piston behind the lever. It wouldn't and it doesn't. 🤦♂️😂
Aw come on.... Has gmbn run out of content since Doddy left? Doddy did a comprehensive video on this 12mths ago? Like with Blake and the ridiculous 36" wheel. Doddy covered that 2 maybe three years ago.... Gcn+ closed, think gmbn will be following suit shortly 😢
Thanks for the cool test! Even without a performance benefit, I like the bigger rotors for the lower force needed on lever pull. This equates to less arm pump on a long descent.
@@MBj1703 Totally agree, locking the rear wheel isn't the most efficient way of stopping. I think the combination of Anna being a light rider and the extra stopping power up front (which would load the front wheel more) meant there wasn't much weight on the rear tyre so it is difficult to stop it from locking up. Next time we will try it with a heavier rider and see how that affects it!🤘
No such thing that is a fallacy. It takes the same amount of lever Force no matter what size the rotor is what you're referring to is torque. Not lever pressure. This is simply your perception but not reality in terms of the laws of mechanical physics
@@rider65 Whatever "you" say. Fact, you need less lever pressure on bigger rotors to generate the same braking power which leads to less fatigue of the fingers and arm pump. It's simple physics 🙂
This is a cool test. Would consider the 220s now for less arm pump. Currently running a 200 and the difference from the 180 is huge even a casual rider like myself was able to notice.
That was the least scientific test ive ever seen. Run on different days, looked to be travelling visually slower on 200s before braking. Since you could lock the 180s at will on any surface there shouldnt be any difference in stopping distance, its just practice and what youre used to. Larger rotors should just give better feel, thats it.
Yep, it didn't even look like she braked very hard, even on the tarmac, I've gone from 200 to 180 and my braking performance hasn't changed, the smaller rotors still have more than enough power to lock the wheel, they just require slightly more squeeze from the lever on very steep descents, just look at the difference in stopping distances on the tarmac between the 180 and 200, there's no way that should ever happen.
Great test! I went to 220 front and rear for a long time now and I’m a light weight rider. Less finger and arm fatigue and fade resistance on long (10min+) steep runs are the main reasons. Also when I ride a ridiculous amount per week it keeps my body get beat up as much. It takes a while to get used to how powerful it is but once your brain adapts the grabbiness is manageable.
Ya Get To Use The ADVANCED Braking Techniques Like Feathering And Trail Braking . I ride Whistler ALL Day Without Arm Pump .... of course im fit and Ride Alot So I dont Brake as much as most riders . Makes For Very Fast Flow
@@rinky_dinky Funny thing... you can get a 180 rotor to lock up on tarmac down a hill... any thing beyond lock up is ... well still locked up... So riding a 180 near locked up down a tarmac hill until you come to a stop is EXACTLY the same load as a 220mm near locked up... so the rating is really a bit of a joke unless they expect you to use brakes on that fork that cannot force the wheel to near stall. I can load my forks on my old Vee Brakes as well as the 200's I run... the Vees just don't have the feel and fade/burn away quicker. The big difference is the Vees required an entire vice grip of fingers vs the 1 finger braking I get with the XT's. (And I ran a Schwalbe Nobby Nic with the vee's so there was a good amount of force back from the tyre grip.
@@rinky_dinky Because you want to go bigger on the rotor, so they want you to go bigger on the forks... and guess who just happens to be selling the next model up... the same people that rated their cheaper ones... There is a point... Bigger rotors, more ease to overload the forks... Like a lot of base $ forks that you could destroy with a good tyre and Vee brakes... I think the big thing is a hard landing with a handfull of big rotor brake will give huge torque to a set of forks where a smaller rotor will be forced into rotating... THEN you will see meaning to the fork rating... If you just ride DH without big air to flat under hard braking... I'll go with my 1st 'theory'. (I used to load the front of the trailbike when I needed to get a bit more 'Stop' without reaching a lockup but generally I was too mediocre to really push a YZ250 to any real limit.. Plenty of big air to flat but always with plenty of runoff.
"For me, bigger is better. I'm using 203 on the front and 180 at the back. It took me some time to get used to the stronger brakes, but the upside is I can brake for much longer. Going down, more material takes longer to heat up, delaying the onset of brake fade." this is a much cheaper way than to invest on Ice tech rotors and finned Pads.
For me, the only real difference I've noticed in going from 180 front to 203 is that my 203s are noisier and I can't figure out why. The only thing I haven't tried at this point is swapping out the pads or rotor entirely. I don't notice any difference in stopping power for my needs, but then again my 180 was on a 27.5 and my 203 is on a 29, so that could be the difference.
I really liked your video, thank you . I would really like to see this test using perhaps a heavier bike with a bigger tire like a full power ebike, I think the benefits of a 220 brake should be very noticeable there.
The brakes should be hotter but cool quicker with increasing radius. The velocity of the disc that contacts the brake is greater as the radius of the brake gets larger, making for greater temps. But the increase in surface area enables them to cool quicker. The ideal larger brake would be if the surface area of the friction pad was increased, not the rotor. Or have dual parallel discs and pads. They are probably on the way
Dual parallel disc would be cool to see! 👀But a bit heavy for MTB I think we could see them appear first on an E-bike but is there really a need for them? 🤷♂
@@floydblandston108 I love my Gustav's on my old Foes Weasel (made it to GMBN mention a couple of times now, see my walkaround vid for a view of the Gustav up front.)...
Not sure your right with the hotter bit... Take it to an extreme (caliper the size of the rim... The disk will have cooled by the time the wheel has done full rotation, but the pads will be hot... but not necessarily as hot as a small rotor as the force will be so much less required.... so less force, more heat dissipation... the rotors should be cooler... The problem I see is that with less modulation, I think Anna may have been riding the brakes a little more to keep 'feel' for them. ( found myself doing that for the few days after getting my 200mm brakes clean and running (when I 1st got them) before switching to 1 finger.. and literally overnight never went back after the 1st 1 finger ride. (which I got on film on about my 3rd U-toob video)
I dont think your area increase calculations are quite right as you dont appear to have worked out how much metal is missing due to all the holes. Because the less metal you have ( because of the holes) the harder you have to 'work' it to obtain the stopping power and then the harder you work it the hotter it gets ! It would be interesting to see different rotas the same size with smaller or even no holes. A easy way to put more metal between the pads. In addition to all this i always use sintered bronze pads ( wet often muddy conditions in the UK) i found them to be better than the fiber originals. I have also swapped the front disc for a solid rota. This gives more feel and power under the heaviest of braking in the dry but does require a turn of the wheel to dry off in the pouring rain. So a 'few' holes are probably preferable.
What size brake discs do you have on your MTB? Do you have the same size for both or mix it up?
200 front 180 rear seems fine with 4 pot xt
Don't know if you read my commentary on the last brake gmbn video, but I explained how brake rotor size has nothing to do with braking power- as far as bigger = more power. A brake rotor in essence is like a heat sink. Surface Friction creates heat which is then absorbed and dissipates heat, converting kinetic energy to thermal energy. What a bigger rotor will do is stave off brake fade more efficiently than a smaller rotor.
Thermal conductivity is the goal. You want pads that can absorb and dissipate the proper amount of heat from the friction to the rotor and still be within an operating range that will optimize braking power. Once the pads have surpassed their efficiency operating temperature they will begin to glaze from overheating and no longer be able to transfer the heat energy to the rotor and vice versa.
If the rotor becomes overheated the pads will absorb excess heat from the rotor as well as heat from the applied forces of friction. And the result is that the friction coefficient will diminish- I.E.- brake fade
@@rider65 - you forgot about leverage. Remember; physics believes in you even if you don't understand it.
@@floydblandston108 😂 nice try their Fredo... leverage can only change from the master cylinder pressure itself. Go back to school Sonny Boy
@@rider65 - it's called 'angular momentum', look it up.
Important point; once your wheel is sliding, you're not testing brakes, but tires.
Exactly. A lot of people think they need more power. You need better heat dissipation, better tires, etc.
Its A Combo Deal ALL depends where you Ride And Skill Level
Ya, once your tires lock up, the entire braking system becomes irrelevant to the conversation of braking distance and control
Once the tyres lock up you are still testing the brakes in real conditions. The back wheel can still jack on trail, especially on a full sus, if the brakes are poor they may not remain locked, also you will modulate to just before the lock up, better modulation and power means your hands won't get as fatigued on longer descents.
@@MyBetsie - she was measuring stopping distance....on pavement.
I’m more impressed by Little Champery on a hard tail than the brake tests themselves 😮
We had to do a proper stress test 🤷♂
A couple of other things to consider here are brake pad composition and how that relates to the rotor temperature ramp up.
Disc brakes need some temperature to function and that temperature is dependent on pad material; resin vs. sintered. The stopping distance test showed that the rear just locks at the pad "bite point", where the pad makes initial grip, and the 220mm rotor took longer to heat and provide the needed stopping power to slow down then the 200mm. The bite point is different between pad materials as is how quickly they heat the rotor up.
If you watch most types of car racing you will notice that the teams change the brake duct sizes to keep their rotor temps in the optimum range. Formula 1 is a good example. If the driver lets the brakes get too cool, they are useless.
What it all comes down to is experimenting to find the best combination of pad material and rotor size that works for the rider and their terrain.
On my hardtail with 2 piston calipers and sintered pads I never felt I needed bigger then a 180/160 front & rear.
Formula 1 brakes are carbon rotors and are designed to operate at high temperatures. Bike brakes are designed with normal riding conditions in mind and will be operational at cooler temperatures. They may not be optimal. The same reason normal car's brakes are metal rotors; they need to work straight away.
Good lord man nobody is reading that novel
I just did
@@DB-sd3cw You should, you'd learn something. Exactly what @dantuttle2050 said is correct.
@@lenolenoleno can't imagine being so lame you have time to comment on a 5 month old reply. No wonder you have time to read that novel, you have nothing else to do it seems
I have the same Shimano MT6100 breaks on my Trek Roscoe with 200mm front and 180mm rear rotors. I also noticed an improvement in breaking and feel from the stock MT200’s and 180mm front rotor it came with. I dont do any downhill trails so this setup works very well for me and didn’t break the bank upgrading. Thanks for the video! 🙏
Locking up the brakes and skidding isn't the most effective way to stop a mountain bike.
Interesting video. Definitely do a part two with a longer test track. Also add in a heat dissipation time. Like heat of rotor right after then another minute after to see how much heat it lost.
Lean back when braking. Also. I've seen tests that were done multiple times in each of your categories and the ones that responded better, was after the first initial braking. As if heating them up at a certain point seems more effective. Excellent job yes
My Trek Fuel EX has 203/180 with TRP 4 piston calipers and they’re perfect for me but when my wife who’s 100 lbs lighter than me rode my bike she hated the brakes because it was so difficult for her to modulate them. She much prefers the Shimano MT200 180/160 on her Polygon Siskiu D7 that feel like mush to me…it’s all very personal.
On my 2015 trek Remedy 7, the stock parts were Shimano deore 2 piston; 180/160 rotors. When I raced and the descent was greater than 5 minutes, I had brake Fad ( big loss of power). I switched to 203/180 seven years ago and have not had one moment of power loss or fad inside and outside of racing!
Sounds like you've got the perfect setup! 👍
As heat builds up in the rotors and pads the "capacity" of the brake system gets filled up and tires get more and more prone to locking up as the energy finds it easier to skid the tires than to turn kinetic energy into heat where there's already a lot of heat built up.
I like to think of the rotors as pools in which I can dump my kinetic energy as heat. The rotor size is the volume of the pool, the heat dissipation is the sink of the pool. The bigger the sink the faster it drains (duh.) and the larger the volume the more speed I can dump into it at once.
It is surprising how many riders are willing to let go of that braking performance for the measly gain of a few grams. Better braking means higher overall speed through confidence, control and safety.
Tire grippiness is what determines how full the pool can get before I start skidding which is to be avoided if we want efficient braking.
Just my 2c.
Try using a bicycle computer for speed start to finish in each run or stopwatch for a more accurate reading.
Thanks great video!🇨🇦
I think for lighter riders like her 220mm doesn't make any sense. As she noticed, they lock up on her too quickly especially in the rear and thus reduce braking efficiency. For me personally a 220mm in the front is the way to go on my Enduro bike, but I'm also quite a bit bigger and heavier than she is. So essentially 220s do for me what 200s do for her her.
Yup , plus I like to be able to lock the rear wheel really easy
PAD Compound IS Key
7:12 "perhaps the 220's where too powerful, we skidded" that is what happened. Once the wheels lockup the tires are no longer able to extract its maximum grip/braking capabilities.
180mm had no skid. 200mm skidded just a bit. 220mm skidded too much to stop maximally.
The larger rotors also have a higher thermal capacity and thus requires higher temps to be optimal.
Just as the video concluded, the bigger the rotor the higher loads are required to get the most benefit(heavier rider and/or DH applications)
@@lukedangles-mckenzie2024 what is your point?
My trails are very short descents and punchy climbs. I could be entirely wrong but I've found that a 160 on the rear spins up heat faster and grabs a lil harder for me in the short braking spurts i deal with at my local trails. I think on a long decent I'd melt it and fly into the trees though. (I'm a wheel bending 285lbs) Something to think about if your descents aren't long at your local trails!
You are correct a smaller rotor will heat up quicker thereby transferring the kinetic heat energy into thermal energy into the pads. For a short period of time a smaller rotor will be more efficient but on any sort of prolonged usage the smaller rotor will no longer be thermally efficient
You should try to descend Khardungla in Ladakh. It's a 5300 m mountain pass which descends to 3500 m on a distance of 40 km. A full hour of descending.
Riding it up is a good training
Drag test would be a good test. Your trail test, yes make it longer, but also do different trails one being a fast flow trail and the other being a slower tech trail.
I'm pretty sure they did but, just in case, were the rotors bedded in properly? That can dramatically affect the performance of the brakes. Also, it would be nice if you could mark the braking point and not only the stopping point. Maybe you did Mark it but it wasn't told in the video. Finally, don't take your foot out of the pedal before the stop has been completed, Anna! That can affect the result as well. Maybe go flat next time, so that you can focus on the braking only.
Just a few suggestions. Love it, guys. Keep'em coming and go Anna!
I think drag brake test on a down hill will be more realistic for the bigger rotor. Great test anyway to show but replacing the rotor itself can really change the entire dynamic of the stopping power & feel.
Exactly. People tend to drag the rear and that's why it wears and heats up so much.
I've got 3 different bikes with 3 different brake discs, and I never felt like I didn't have enough brakes. I haven't ridden my new Pivot Switchblade yet, but it's got the biggest brakes of the three with 203mm in front and a 180mm rear, but with 4 piston STX calipers front and back. I'm sure the braking will be ruthless. I have no desire to change rotors on any of them. The front brake is supposed to be doing like 70% of the power, you definitely seem to favor your back brake. I've had quite a few motorcycles, and the last one I owned had dual 320mm rotors up front with 4 piston Brembo calipers on it, and just a single 220mm rotor in back with a two-piston caliper because the front is where the power comes from. During the panic stop testing, you could have used the front brake harder instead of locking up the rear and dragging the tire. I know in the loose stuff you're worried about losing the front end, but there's more front squeeze to be had IMO. ;)
It is not up for debate or doubt. Always the front disc has a larger diameter. Even with cars. A matter of angular velocity
Except on downhill MTB where you use more rear brake
@@janeblogs324 Correct.
I know people that run larger rear brake rotors for downhill or so they can easily lock up the rear fast and easy
Regardless of front or rear disc, the larger diameter disc has better braking capabilities.
Size makes such a difference I remember way back when I saw one of the bigger boys light a fag/cig off his160mm hope mini after his lighter died then years later a rider who was also there found 180mm just didn't get hot enough to pull off the tame trick
Stay tuned for the next videos within the series "is physics even real?" featuring bangers such as "does gravity affect descending?" and "will more suspension travel result in more suspension travel?"
I would think that your idea of science doesn't match this video. Larger rotor size does in fact affect braking performance. It all depends on how you ride and your equipment.
@topcat304 what? That is more than obvious, which is why the video is redundant
No matter the size I keep warping rotors.
But some reasons for that can be sticky pistons, so lube the pistons.
Rebuild caliper with new seals if needed. Only do that hwen they leak and get stuck even with lubing.
I gone side is sticking there will be a bad brake feel and pad will have a gap between the rotor. And other sid eiwll bend the rotor. But even with perfectly working brakes I keep bending rotors.
I run 223mm rotors front and rear.
In warp rotors less with bigger rotors but still do it. I ran 180mm rear, 203mm front Hope Tech floating rotors. Now I run 223mm Trickstuff rotors. I opted for rotor with no rivets for no creaking, got them second hand offered to me for half of retail so had to try it.
Hope floating rotors defenitly perform much better than resin only rotors in same size, I've had 160 rear 180 front on my previous bike. So massive upgrade. But after years of use it creaked in the rivets.
I would take this test with a very large grain of salt, braking performance on dirt is almost always limited by grip, not by how big your rotors are, I've gone from 200mm down to 180mm and my braking performance hasn't changed, the only thing that has changed is the smaller disc requires slightly more squeeze from the lever on very steep descents, maybe the issue is the weak 2 piston calipers? they probably can't get away with running a 180mm rotor.
I have two similarly equiped bikes, but one is a hardtail, the other a fullsus. Both have 203 up front. The fullsus also has a 203 rear I kept the rear down to 180. One of the hardtails biggest drawbacks is braking on lose, chattery terrain because the rear starts to bounce and skid. I feel a larger rear rotor would make it skid more.
I agree... You could try harder pads to decrease grip to the rear... I still think that rear brakes are overrated and you can be a better rider the less you can force yourself to use them.. but that comes from years of motorbike riding where onroad rear brakes are actually dangerous (a lot of racers make them near useless so they don't accidently use them in a race) and on the trailbikes I became faster on my old bike when the drum rear failed and I learnt how to brake hard upto a corner and no brakes through it (to the point where I was entering corners with the rear in the air (which is why I say rear brakes are useless (Except for stopping at slow speeds like lights.
Thanks for the video,
Stop distance, heat & times are always going to be 'rubbery', you'd have to go a brake dyno & thermal camera,
FEEL - or modulation - i think is key, the harder you have to squeeze - the less FEEL, so go bigger
Also you taught us we need to bed-in the rotors with pad material??
no 160s? entry level starts there in my eyes. I did go from 160 to 180 in the front and found better power on tarmac
I find with big rotors I set my levers to bite close to the bars. This stops lockups unless you really grab a handful. Way better modulation.
Awesome video love your Nuke Proof hardtail.I use 180mm front 160mm rear.Super strong combo.💯💪🏻🚴♀️
Upgraded my Slash 8 180/200 to 200/220 after my brakes were overheating on longer runs. 10 minutes plus. Made a huge difference, with no overheating. I also like the sensitive braking, which some people may not like.
Sounds spot on! You can always switch to a braking system like Srams where the modulation is far greater giving a less sensitive lever feel, but easier to modulate power.
I Had a similar Problem with my Cube one 77, solved IT with a 200mm Rotor at the rear.
The distance test is subject to far too many variables such as initial speed, surface temp and modulation of the brake and as such can be misleading, to understand which brake produces the most braking you need to do a G force test with a G meter and do multiple runs to produce a bell curve, this way you get a clearer picture of the brakes performance.
the braking limit of the bike is not the brake disc and caliper but the coefficient of friction of the tyre to surface, a small brake can lock up on mud for instance.
you also have to factor in the weight of the rider bike combination, a 60kg rider on the same weight bike as a 100kg rider produces vastly less kinetic energy at the same speed, so to produce the same G rating under braking a heavier rider will require a larger brake.
Some riders will prefer a more sensitive brake lever that is lighter to modulate and control, that lends itself to a bigger brake whereas other prefer a brake they can grab without lock up, opposite requirements.
Then we get into the kinetic issues such as weight transfer, a taller rider will have a higher center of gravity than a shorter rider and therfore transfer more weight to the front wheel under braking requiring a larger brake, all of which is subject to our initial starting point of the coefficient of the tyre, which as mentioned earlier is the limiting factor.
suffice to say you have to tailor your brake sizing to your own requirements, the only given factor is, due to weight transfer to the front you can reliably use a smaller disc at the rear to control lock up as weight and therefore friction is reduced by weight transfer under heavy braking.
On my own bike I use a 203mm disc and 4pot caliper on the front and a 160mm with 2pot on the rear, this is because I am 6ft 2" tall and weigh 105kg,
I've put a bigger rotor on the front and a smaller one on the rear than the stock setup. There was too much power on the rear for the amount of grip that wheel has, making it hard to modulate to the point of lock up. I suspect bikes coming with too much rear braking power is why we have so many braking bumps at trail centres!
That's something to think about! 🤔
Hope floating/ventilated 203 front & rear on both of my V10s. Tech 3 brakes on 1 bike & Tech 4 on other.
I have 180 mm disc brakes on both wheels,with a pair to 2 pot brakes on the Hardtail,is a lot of stopping power
Horses for courses. On my enduro bike I'm happy with 203mm front and 180mm rear. Tried 203mm rear with a four piston Zee and it was actually too much brake for me on pretty steep trails. Finger rest on the lever in the air would start locking up the rear and then dip your nose on jumps.
Combination of quality caliper and adequate rotor size makes more sense than just upspeccing rotors. On DH bikes, or enduro racing, then by all means, 203 or 220 makes sense, but I think there is a thing like too much brake for purpose.
What about rotor thickness and two piece vs one piece rotors? A huge deal with going bigger is that it's easier to warp rotors under hard braking
I don't think brake size would help in this test other than lever effort. The main advantage of big rotors is their ability to absorb and dissipate heat in multiple stops
There is no change in lever effort at all because that would mean you'd have to change the ratio in the master cylinder as it pushes the hydraulic fluid through the caliper into the Pistons. It's a fallacy. It's simply psychological perception
@@rider65 A bigger diameter rotor is moving faster through the caliper (or has more leverage on the hub). Therefore, you need to squeeze the lever less for the same level of braking force.
@@rider65 Another way of saying this is that a given level of lever effort will result in more braking force if you have larger rotors.
Next time avoid locking the rear tire specially on asphalt, that situation show that brake balance is not well performed and modulation is not executed properly.
Removing those mistakes will provide more accurate results
I would love to see a drag brake test, especiallyon the rear. Get it up tp speed in a controlled Environment and drag the same distance. Maybe also how quick the rotor is cooling down in 15, 30 seconds.
Nothing was noted about tire grip. Your tires have a lot to do with how effective your braking is. GALFER makes a 243mm rotor. Overkill unless you're doing a bomb run down Pikes Peak. IMO, 220/203 is a good combo for aggressive enduro/DH riding for riders over 180lbs. Why would anyone gage their bike performance on EWS or XC racers. It's all about feel and performance on the trail.
I used to think always bigger the better but I came back to 203 up front and 180 rear for optimal balance of raw power.
That would be a fun test, playing with size combinations like 160 up front 220 rear! Drift machine?
If you really want to get an idea of heating and cooling, The Bike Sauce channel put a data logger on his disc and did testing on a road for consistent, hard braking.
I've been meaning to repeat this to compare Ice Tech to cheap rotors... Heat dissipation rate.
50C is nothing to be excited about. Heck, sometimes the ambient temperature is 38C. I've measured 100C without fade. Pretty sure pads and oil are rated well above that.
If you temper stainless steel it gets different colours. It gets the same colours if it heats up at braking. If parts of the disc reach 200° they get yellow, if they get blue they are more near 300 °.
My disc rotors are yellow beside the braking surface.
Love you anna.just had a s-works epic ht built for me,and these are always 160,mm rotors with xt brakes,find myseld doing a traffic copper running commentry,stop stop stop,this has made me think.maybe look to go to 180 mm front and rear,bit surely brake compounds play a part too❤
@GMBNtech..... Hi guys. at 12.09 caption said "REAR DIC BRAKE" (220mm rotors) ???? Wasn't this proofread before posting? Was this overlooked? It's the first time that this happened!
@gmbntech could we hear a little more about the hardtail you were using for the test, I noticed you didn’t have a fox or rockshox fork. Great job Anna as always!
as @floydblandston108 said - while braking you didn't really change the way you modulate (or did not modulate at all) nor your body position. There was very little gain in braking if you don't actually use the grip of tires. I was surprised that you didn't pay attention to that more, you know better! :) Braking distance should be measured ONLY if you did not skid.
also forth mentioning that not all discs have same surface and is not acting same with all types of pads + include the 'bed in' period required and etc... there are quite a few variables, but for the purpose of this video - the point was made! :)
Very interesting video anyway! I am happy with my Magura MT5 with 203 up front
Realistically, you can lock your wheels with either size, so the braking power is there in all cases and it's limited by traction, i.e. tyre/terrain combo.
The size difference matters technically only as far as heat management is concerned. Dissipation is a function of surface area and one can easily have a minimalistic 203mm rotor with less surface than a bulky 180mm rotor.
Regarding heat accumulation, a bigger rotor will always have more braking surface (larger circumference that comes in contact with the braking pads), so it should heat up slower than a smaller rotor.
Larger rotors provide different feel due to modulation, which isn't really bike (or rotor) performance, but rather rider performance. Note that in all cases the contact surface is the same since it's determined by the pads' size, so the difference in modulation is only due to the radius, i.e. you are playing with leverage - that's literally like changing the length of your brake levers.
Amazing test. Thanks for share.
Interesting ...what about cheap cable brakes with bigger discs ? ( more likely what I'd do 😊 lol )
The main reason for bigger discs is for higher speed tracks,DH types & heavy bikes & riders....eg; e-mtb's ..I'm 78kgs on a 25kg e-mtb so 223mm front & rear give me a lot more control.....steering & braking.
You need to do this on a full suspension bike for real reaults to compare to why enduro racers use 220mm rotors. Hand farigue, especially with basic brakes makes a big difference on longer runs too.
I run 180 Ice Techs on both my Trail and AM bike with the AM bike getting 4 piston calipers. I've tried a 203 in front on the AM bike and not a huge difference for me.
Anna ist die Beste! 😊
180s work for me but would like to have a 4pot on the front
If you are a heavier rider, like 85/90 kilos and more and you ride steep and long tracks bigger is better, I changed from 200mm center line in the front to 220 hs2 rotor, I don't feel much more braking power, but there is a difference, and a thicker rotor is a good thing too 🙂
Would be smart to mention, that the 220mm rotors for YOU were inconclusive compared to the 203mm ones. I say for YOU, because you weigh (let's say) 50kgs, but for a 100kg rider, a 220mm rotor may be even less "powerful" as the 203mm for you.
Also you (pretty nicely nailed) mentioned the grip of the wheels (tires) that you need for those bigger rotors to "shine". On tarmac, with that knobby tires you have everything, but grip.
And the last one: you compared some "bedded in" discs to some brand new ones. The brake pads needs to "wear together" with the discs, which needs a bit more time (miles) to offer the maximum of their potential.
Ultimately: the "heat check" was also inconsistent. If you're curious about that, you should not ride them on a trail, then you measure 'em yourself, hopping down from the bike. For this test should be more accurate a longer and steep descent (for even more consistency a paved road), where you brake your bike to a certain speed, and maintain that speed (for example 25 km/h) from top to bottom. Then someone should wait for you with a switched on heat measurement tool at the "finish line", for immediate "reading". As you've noticed, these rotors cools down pretty quickly, so every second counts.
Recommendation for a future, even more accurate test: be more constant in measurements, speeds, disc/brake pad conditions, and you could involve (at least) 2 more riders (a 75kg, and a 100kg one) for demonstrate which rotor is the best for your audience.
Cheers!
PS: switching from a 203mm rotor to a 220mm one is a 8.78% increase of braking surface area (you have to calculate the contact surface with a brae pad, not just a line -> circumference of a circle). And yes, I said 203mm, because Shimano SLX rotors are available in 160, 180, 203, and 220mm variants. There's no 200mm option.
#askgmbntech Can 4 piston calipers be used with Acera levers? The nut on the valve stem to tighten it to the rim are instructed to only finger tighten, but what happens if you can't get a seal. I noticed that Problem Solvers has a wing nut looking nut to put more tourq on the nut. Why would this be any different then carefully using plyers to tighten the nut
Thanks Anna, good info. I'm trying to get into doing my own bike work. If i upgrade my 180 rear to 200 to match the front is anything more required than just bolting it on?
It depends if your frame uses post-mount or flat-mount brakes (Different bolt distances), you would need a specific adapter depending on the mount type and rotor.
If your not getting the pads up in temp due to excessive power for the riders weight, style, tire grip and speed then they wont perform as well as say a 180mm.
So, here's a quick tip - not always need to Size Up in rotor diameter - try just getting one of the ticker ones, same size. I changed from 200mm diametr SRAM Centreline - 1.85mm thick to SRAM HS2 2mm thickness - same pistons and callipers - massive stopping power differnce. You don't always need to go larger diameter - so no extra adapter needed either. simples. 🙂
Who remembers those horseshoe shaped stiffening things for cantilevered brakes? We’ve come a ways since then…
I like my rotors big, but keeping them true, clean, and non-mooing becomes harder with size.
A set of 160's run hot with grippy pads wears out faster, but every metric but maximal braking power is more enjoyable. Brakes *like* some heat...
You seem to be stating percentage increase of rotor diameter, not actual surface size, which would be greater than the % you stated.
Old car guy here....if you are going to track day your car, the first thing you did was mount the biggest brakes you could fit on the car. my e bike and my mountain bike both have 220 rotors.
I love you guys, but I rly miss the more science based approach where you take out variables.
Anna is only human so how about we equip the bike with abs, do every test indoors, on clean tarmac, same weight distribution etc. Thn maybe we can see exactly where a bigger disc is making the biggest difference aside from finger feel. I'm a super lightweight rider that just uses cheap shimano mt400 stuff on 160mm discs and I haven't encountered a situation where I needed more braking power (in the Netherlands) but I also have higher than average grip strength...the strength that can pull v-brake cables out (happened a few times) and it's personally a big reason to go for hydraulics, the extra modulation is also rly nice..but yes, I never experienced high end brakes and I can heat up a disc in about 30 seconds to the point it might burn you when touching
I’m 100kgs in my birthday suit and my 220s are great. The SRAMs I have were so weak even with 200s it felt like I had no power. 240s next 😂
Code r 4 pots by the way
Do you normally ride without gloves?
It's physically impossible for larger rotors to cool down faster (all things being equal)
I'm pretty sure, that is not a heat gun. A heat gun would increase the temperature in the rotors and not measure it.
I love this channel very much, however this test is unfortunately inaccurate considering the rear tyre was sliding almost the full duration of each brake test, the idea of testing rotors is not to see if it will lock up the wheels but to see how quickly they will take you from whatever speed down to zero with the least amount of wheel lock up possible. With proper braking technique you should be able to apply just enough brake force on each wheel to just where the wheel is about to lock up but never actually does to give you maximum braking force with each lever pull.
High speeds are where more power brakes make the difference. Think 20 mph +
You were clearly locking up the rear with 220 whereas the 200 was acting like ABS during emergency braking. Didn't look like you locked the front at any time and could use more power there. A wet test would be good to see how easy you can modulate the front without locking it up.
223 front with 203 rear with 4 pot is the sweetest spot 😊
An IR themometer cannot give accurate measurements of a shiny surface.
Those are 203mm discs not 200 as stated. Jus sayin.
Hasn't all this been tested and verified already?
I can feel engineer and technicians crying at the use of the term science 😂 I run what my LBS Sensei mechanic suggests. FYI I run 220 F&R on my e-bike, 203 F&R on my enduro and 180 on DJ bike. I’m 6’5”, 96kgs 🤘❤️🌈🕊️🌎
What happened to dody?
He works now for a bike company. He was not fired, he got the job offer and chose to do it.
Larger rotors allow for a lighter lever pull, less aggressive pads, and faster heat dissipation. There really is no down side other than cost
No they don't. Why would a larger rotor affect or change the ratio of the hydraulic fluid in the master cylinder and the Piston behind the lever. It wouldn't and it doesn't. 🤦♂️😂
@@rider65 I will refrain from snarking and just say you need to learn how a lever works.
Your cables are driving me crazy going down hill . They need a trim ✂️.
If only we could bath the rotors in nitrogen and use magnetic braking using eddy currents. 😂
Pretty soon rotors will be half the size of the wheel.
Or fully the size of the wheel. Called rim brakes.
@@dicktiionary hydraulic rim brakes lol
@@RedWingsninetyone lol, and nice heavy stainless steel rims so they don't get crushed
@@dicktiionary to cut down on the weight and help increase the length of the contact patch they'll make the tires narrower
@RedWingsninetyone got you! Dh on my road bike. It will be Amazing!
Get some basic understanding of the principles of physics first Anna. This test is so wrong in so many ways.
Aw come on.... Has gmbn run out of content since Doddy left? Doddy did a comprehensive video on this 12mths ago?
Like with Blake and the ridiculous 36" wheel. Doddy covered that 2 maybe three years ago....
Gcn+ closed, think gmbn will be following suit shortly 😢
ppl call me crazy to run my bike with 246mm Rotors. I'm 120kg ... when 60kg riders think 220mm are fine ... I'm def allowed to run my 246mm :D
Thanks for the cool test! Even without a performance benefit, I like the bigger rotors for the lower force needed on lever pull. This equates to less arm pump on a long descent.
Agreed this is my reason as well.
same here, went to 223 for less force needed and less arm pump. PS: blocking rear wheel makes no sense for a breaking test ;-)
@@MBj1703 Totally agree, locking the rear wheel isn't the most efficient way of stopping. I think the combination of Anna being a light rider and the extra stopping power up front (which would load the front wheel more) meant there wasn't much weight on the rear tyre so it is difficult to stop it from locking up. Next time we will try it with a heavier rider and see how that affects it!🤘
No such thing that is a fallacy. It takes the same amount of lever Force no matter what size the rotor is what you're referring to is torque. Not lever pressure. This is simply your perception but not reality in terms of the laws of mechanical physics
@@rider65 Whatever "you" say. Fact, you need less lever pressure on bigger rotors to generate the same braking power which leads to less fatigue of the fingers and arm pump. It's simple physics 🙂
This is a cool test. Would consider the 220s now for less arm pump. Currently running a 200 and the difference from the 180 is huge even a casual rider like myself was able to notice.
That was the least scientific test ive ever seen. Run on different days, looked to be travelling visually slower on 200s before braking. Since you could lock the 180s at will on any surface there shouldnt be any difference in stopping distance, its just practice and what youre used to. Larger rotors should just give better feel, thats it.
Yep, it didn't even look like she braked very hard, even on the tarmac, I've gone from 200 to 180 and my braking performance hasn't changed, the smaller rotors still have more than enough power to lock the wheel, they just require slightly more squeeze from the lever on very steep descents, just look at the difference in stopping distances on the tarmac between the 180 and 200, there's no way that should ever happen.
We’re all rotors bedded exactly the same?
Great test! I went to 220 front and rear for a long time now and I’m a light weight rider. Less finger and arm fatigue and fade resistance on long (10min+) steep runs are the main reasons. Also when I ride a ridiculous amount per week it keeps my body get beat up as much. It takes a while to get used to how powerful it is but once your brain adapts the grabbiness is manageable.
Very few forks and frames are rated past 203 mm you're not worried about things breaking?
Ya Get To Use The ADVANCED Braking Techniques Like Feathering And Trail Braking . I ride Whistler ALL Day Without Arm Pump .... of course im fit and Ride Alot So I dont Brake as much as most riders . Makes For Very Fast Flow
@@rinky_dinky Funny thing... you can get a 180 rotor to lock up on tarmac down a hill... any thing beyond lock up is ... well still locked up...
So riding a 180 near locked up down a tarmac hill until you come to a stop is EXACTLY the same load as a 220mm near locked up... so the rating is really a bit of a joke unless they expect you to use brakes on that fork that cannot force the wheel to near stall.
I can load my forks on my old Vee Brakes as well as the 200's I run... the Vees just don't have the feel and fade/burn away quicker. The big difference is the Vees required an entire vice grip of fingers vs the 1 finger braking I get with the XT's.
(And I ran a Schwalbe Nobby Nic with the vee's so there was a good amount of force back from the tyre grip.
@@TheButlerNZ wow I've never thought of it like that , you've got a good point , but why do bike manufacturers put a max rotor size though ?
@@rinky_dinky Because you want to go bigger on the rotor, so they want you to go bigger on the forks... and guess who just happens to be selling the next model up... the same people that rated their cheaper ones...
There is a point... Bigger rotors, more ease to overload the forks... Like a lot of base $ forks that you could destroy with a good tyre and Vee brakes...
I think the big thing is a hard landing with a handfull of big rotor brake will give huge torque to a set of forks where a smaller rotor will be forced into rotating... THEN you will see meaning to the fork rating... If you just ride DH without big air to flat under hard braking... I'll go with my 1st 'theory'.
(I used to load the front of the trailbike when I needed to get a bit more 'Stop' without reaching a lockup but generally I was too mediocre to really push a YZ250 to any real limit.. Plenty of big air to flat but always with plenty of runoff.
"For me, bigger is better. I'm using 203 on the front and 180 at the back. It took me some time to get used to the stronger brakes, but the upside is I can brake for much longer. Going down, more material takes longer to heat up, delaying the onset of brake fade." this is a much cheaper way than to invest on Ice tech rotors and finned Pads.
For me, the only real difference I've noticed in going from 180 front to 203 is that my 203s are noisier and I can't figure out why. The only thing I haven't tried at this point is swapping out the pads or rotor entirely.
I don't notice any difference in stopping power for my needs, but then again my 180 was on a 27.5 and my 203 is on a 29, so that could be the difference.
I really liked your video, thank you . I would really like to see this test using perhaps a heavier bike with a bigger tire like a full power ebike, I think the benefits of a 220 brake should be very noticeable there.
The brakes should be hotter but cool quicker with increasing radius. The velocity of the disc that contacts the brake is greater as the radius of the brake gets larger, making for greater temps. But the increase in surface area enables them to cool quicker. The ideal larger brake would be if the surface area of the friction pad was increased, not the rotor. Or have dual parallel discs and pads. They are probably on the way
Dual parallel disc would be cool to see! 👀But a bit heavy for MTB I think we could see them appear first on an E-bike but is there really a need for them? 🤷♂
@@gmbntech - We'd be better off first going back to Magura's 'Gustav' sliding caliper system.
@@floydblandston108 I love my Gustav's on my old Foes Weasel (made it to GMBN mention a couple of times now, see my walkaround vid for a view of the Gustav up front.)...
Not sure your right with the hotter bit... Take it to an extreme (caliper the size of the rim... The disk will have cooled by the time the wheel has done full rotation, but the pads will be hot... but not necessarily as hot as a small rotor as the force will be so much less required....
so less force, more heat dissipation... the rotors should be cooler...
The problem I see is that with less modulation, I think Anna may have been riding the brakes a little more to keep 'feel' for them.
( found myself doing that for the few days after getting my 200mm brakes clean and running (when I 1st got them) before switching to 1 finger.. and literally overnight never went back after the 1st 1 finger ride. (which I got on film on about my 3rd U-toob video)
The rider is going to be a big factor as well as just getting use to how they feel
Reducing the fatigue in your forearms and losing brake fade were the two things on my mind with this.
Ive had my discs glowing red in the alps
Same experience here. Running 203s. 220 is too strong, I find myself locking the wheels too often.
I’m just here for the weird sounds coming out of her mouth… thought I was the only one who did that. 😂😂😂
I run 180 front and rear on both bikes
I dont think your area increase calculations are quite right as you dont appear to have worked out how much metal is missing due to all the holes. Because the less metal you have ( because of the holes) the harder you have to 'work' it to obtain the stopping power and then the harder you work it the hotter it gets ! It would be interesting to see different rotas the same size with smaller or even no holes. A easy way to put more metal between the pads. In addition to all this i always use sintered bronze pads ( wet often muddy conditions in the UK) i found them to be better than the fiber originals. I have also swapped the front disc for a solid rota. This gives more feel and power under the heaviest of braking in the dry but does require a turn of the wheel to dry off in the pouring rain. So a 'few' holes are probably preferable.
You have to account for the hole's friction, think cheese grater 😂
Psi, pounds per square inch. Less metal= more force
@@LaurentiusTriarius 🧀😂
@@janeblogs324=Greater rate of wear.