The Myth of Suspension Preload (FM Live)
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- Опубліковано 23 січ 2020
- This week on FM Live, our resident suspension guru, Keith Tanner, talks to us about suspension preload and the nuances of coilover suspension for our favorite roadster.
Original live video recorded 1-23-20. Join us every Thursday at 2:00 PM Mountain time for new live content!
Flyin' Miata is the world leader in Miata performance. We offer a wide range of parts for all years of the Mazda MX-5 Miata.
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These videos are hidden gems...for now. 🏎💨
Still hidden
And still hidden.
im so glad i watched this before purchasing my suspension. great information
Glad we could help!
Awesome video. I used to argue endlessly over on Honda Tech about spring preload and how it does nothing once the car weight is on it. Love the comparison of one vs 2 piece shocks. For years I’ve thought the 2 piece was better as ride height adjust without changing travel. And that may be okay on Honda’s but on Miatas it’s obviously a different story.
You guys helped me diagnose coil bind - much thanks!
this video really helps me to get a better understanding on how coilovers work. followed advice and my ride quality significantly improves. goes to show that most people(including me) dont know what were really doing when 1st "tuning" coilovers. tq very much.
We're really glad it helped you improve your car! That's the whole point.
Just placed an order for my NC miata!!! (Track version) can't wait!!!
This is crazy scary correct info. I just installed a set of coilovers and tried to set ride height both ways. Guess which one turned out with a more predictable result? Using the spring perch instead of shock body. The amount of sag with the common preload of 3-5mm was almost making the coilover useless. It just makes sense.... every strut I've seen taken apart required the spring to be compressed. The amount of people setting up all of these two piece coilovers wrong is crazy to think about.
thank you! Excellent explanation!
Great explanation...currently looking to revamp my "tired" coilover setup (Tokico Illuminas/Groundcontrol/Eiback springs-375/250).
FM V-Maxx(?) of similar rate are calling me...
Great info because I need to get off these racelands, and this summer I want to daily my 90 NA in north New Jersey/nyc.
That's funny, the upstate NY streets i'm on has lead me here as well.
i.m not a suspension guy but the lessons I've gotten in the past few days has nearly sold me on the FOX.
@@miatafan I'm no expert but on on the softer ground control coilovers and they work great for me on the street/bit of autocross. Comfortable enough to daily even with a lotus seat with almost no padding.
y'all put out a lot of great informative content but this is one of the best and most eye opening ones
Thanks! We were getting a lot of questions about this and figured we'd try and clear the air some.
This is really good. Coming from far east, i always thought the bodyshift is only to adjust ride height with effecting preload. Didnt know it have quite an effect with the shock travel
8:26 "It's a way to market a design choice..." Wow, I'm absolutely stunned that this is what we have to deal with as consumers. I'm so glad i watched this video. Thanks so much!
I'm still astonished, and getting a little pissed haha Fast and furious commercialism at its finest!
Additionally, the two piece shock... THE ENTIRE PREMISE IS TO BE ABLE TO EASILY REPLACE THE SHOCK. But the design likely causes premature shock failure to begin with AND have you ever seen these people in the product review comments calling these manufacturers trying to get a replacement shock? CRICKETS. Queue the middle finger/get over it memes.
I'm in the market for some coilovers for my nc... you just answered my questions, oh&&%, vs fox... thanks! Soon I will call you guys to order mine.
Thanks! Let us know if there is anything else we can help with!
awesome explanation
Would be neat to explain preferred spring rate in relation to performance street tires vs 200 treadwear vs 0 treadwear vs additional downforce maybe :) ps awesome presentations as always!! Thanks for the resourcefulness
Agreed
Gotta get me a set of those fox ,thanks mate
I always loved the Mazda RX8 that I owned because despite being a sporty car it rode brilliantly because it was designed to have a relatively long suspension travel. It made the handling very forgiving too, especially on bumpy and narrow British backroads. I'm 100% convinced that it makes all the difference.
The rx8 has the same design as miatas, therefore the rear suffers just as miatas do. Ask me how I know.
I drive c6 z06s, one of them set up for road racing...(I know what legit good handling is)...and I was VERY surprised at how well an rx-8 I once fixed up performed on curvy backroads. The rx-8s are impressive handling cars in stock form. Too bad the engines are...ya know... "like that" 😏 Maybe my reference point could be a little skewed...but that car was brutally underpowered. Like, shockingly so.
But hey, good handlez tho ¯\_(ツ)_/¯
I just learned so much. My lowering springs on stock length struts choice makes me feel like I made the right decision. 😂😂
We're very glad to hear that!
Great info. So glad you decided to build this channel out. I'm sure it'll pay dividends to your buisness
This explanation is gold.
Coming from the offroad industry where coils are almost always progressive rate, I'm so used to making ride height adjustments through the spring collar.
Now that I'm putting coilovers on a car, I didn't even consider how the coils are single rate and won't make any difference to ride height.
So at the end of the day, when installing coilovers for a car, the only thing to be concerned about when setting the spring is coil bind... which would take a pretty hefty amount of preload and should be easy enough to avoid anyway lol.
Thanks for the video! But I do have a couple questions...
Do cars ever use progressive rate springs?
And if not, why not? Seems advantageous when it comes to road racing with higher or lower g turns and handling characteristics throught said different turns on the course.
Some cars do use progressive rate springs. It's harder to get the damping right as the spring rate is always changing, and the increase in spring rate with bumps can lead to some odd handling at the limit. They're most likely to be used when ride quality is the primary focus.
Interesting video. The lesson about suspension travel was learned many years ago by Colin Chapman who endowed his Lotus cars with soft springing, firm damping and lots of travel when everyone else in that era was making everything solid in the vintage fashion. Re preload, is it not the case that it does affect ride quality to some degree on bumpy roads? With a little preload, the spring will work in both directions, and follow the contour of the road better. The Lotus Elans and Europas all had preload in their springs back in the day. On racing motorcycles they are always playing with preload!
The only time preload comes into play on the road is when the wheel has been completely unloaded (lifted off the ground). The preload will affect how much load will be required to start the suspension moving again. But as long as your wheels stay grounded, it has no effect. The load of the car on the springs makes them "work in both directions".
Motorcycles, of course, have massive weight transfer and will unload front (and rear!) wheels regularly. So the preload will have an effect on how the bike behaves when the wheel comes back to earth.
@@FlyinMiataVideo Thanks for the explanation, I get it a little better now.
I wish I had seen it earlier!
Starting at 7:50, where Keith answers the question about how to set up an adjustable body damper (set it to be as short as possible, while avoiding hitting anything, and then adjust ride height with the spring perch). So, some questions about that response:
- First is regarding the statement about avoiding hitting anything. So, I assume you mean that by making the damper body as short as possible, you’re setting the ride height as low as possible (before adjusting height via the spring perch). Is that correct? So, you’re basically eliminating that ‘gap’ between the bottom of the damper and the bottom of the lower mount?
- Second, regarding the adjustment of ride height via the spring perch. So, when you end up adjusting the ride height to the desired height, what is the desired position of the damper piston at static height? Should it be at 50% (midpoint travel distance, for equal bump and droop travel)? Or should it be positioned for more bump or droop travel (so say, 40% of damper travel distance, or 60% of damper travel distance), to favor more bump or droop travel?
- Third, if you find that, at the shortest damper body length (via the adjustable bottom mount) and with the desired ride height set via the spring perch, that the damper piston position is not in the desired place (as asked in the question above), does that mean that the spring LENGTH needs to be changed (longer or shorter) in order to place the damper position at the right place at static ride height?
1. When you're setting the shock body short, you're not setting the ride height yet. What you're trying to do is get as much bump travel as possible. In the rear, this will mean the shortest length you can manage. In the front, you usually don't bottom out the adjustment as the shock body is considerably longer.
2. Typically, we shoot for about 2/3 bump and 1/3 droop. But for street and track Miatas, what you realistically need is "as much bump as possible" because that's where they're limited. If you're building a rock crawler or a lifted Miata, you may end up with different desired geometry.
3. See above. This isn't really a situation you'll come across unless the damper is tragically short on overall travel, in which case the correct solution is a shock with more shaft travel. The workaround is to give up some of that bump travel to get some droop back - you do that by lengthening the body. You're compromising the car, but it's a matter of compromising one aspect to avoid a complete disaster in another. We have seen it in big name Miata suspension from well-regarded vendors, coilovers that are fully extended at full droop. Changing spring length really only moves the perch position all else being equal.
On a Linear shock, sure. Digressive I feel it may play a little more roll. Recently played with this myself. With a loose preload, it stayed more so in the low speed firmness area of the valving it felt. It was quite rough and a bit harsh, really. Even on the littlest of things. Unpleasant is a great word. Then, I put the shock back at the manufactures recommended preload setting. Or, 'tighter' in lack of better term. Then the valving was perfect! Soaked up everything extremely well. Not unpleasant in any way, shape or form. Quite dramatic of a change, really, from a couple mm change of something advertised to not make a difference. Loose setting, on the same mountain pass with the same valving 'click' adjustment, it was very unsettled. Adjusted back to recommended tolerance, everything else the same in terms of click/rideheight, very confidence inspiring. Idk the exact science that came from this, but I was curious on the topic and explored during a free day. Just commenting my findings 👍
Kyle Gibson shock valving doesn’t come in to it. Once the spring starts to compress, the amount of “preload” ceases to matter. You did adjust the amount of compression travel in your testing and that will definitely have an effect on car behavior. It’s likely that’s what you were experiencing. If I understand your description properly, when you increased your preload without changing ride height, you had to shorten the shock body. That gave you more compression travel and kept you off the bumpstops more. The preload increase wasn’t the real change, that was a side effect.
@@FlyinMiataVideo thank you. That does make sense 👍
Good vid.
Or, what if the left front and right front of the vehicle have a weight difference of 200 pounds in a transversely mounted engine type car or otherwise? Are the spings on Left and right different?
what kind of ride height could you expect out of the FOX ON an NA/NB setup like you said with some preload and no helper springs?
That's not really the way to look at it. What you need to do is decide where you want the car to be, then select the springs accordingly for rate and length. Or choose your spring rate and then choose an appropriate ride height.
The Fox can run above stock ride height. If you're looking to build an offroad car, you'll want long, soft springs. It's probably best if you give us a call to figure out the best setup for your goals.
How do u adj. Preload when Eibach pro2 are installed on the vehicle?
Coming from the motorcycle world it shocks me (haha) how 99% of car enthusiasts dont understand that a shock should have a static sag of around 30% its available travel. Preload is the only way to achieve this considering your spring rate is at least roughly correct for your vehicles weight.
Too much preload = not enough static sag = wheel not able to drop into potholes and such = loss of traction
Too little preload = too much static sag = loss of available travel for compression impacts and hitting the bump stop = loss of traction
30% is standard because its a good compromise.
I loved your video on corner balancing, i used it to build an Excel doc that does all the calculations automatically for corner balancing the sprung weight on my s15 (because i didnt have scales) but im highly surprised you think preload doesnt matter
Id be happy to send you my doc so you can input some basic measurements for the miata and see how preload affects things
You’re making the common mistake that preload is what is affecting your sag. Really, it’s perch height, spring rate and spring length which means ride height. Preload is sort of a sideways way to measure that under one specific condition - full shock extension. The effects you’re attributing to “preload” are actually compression vs droop travel, and they hold regardless of what the preload on the spring is.
Cars have a limited range of suspension travel. Sports cars like the Miata generally need as much compression travel as they can get, so sacrificing it for droop is not an effective setup. One big difference between bikes and cars is the extreme amount of longitudinal weight transfer in a bike - short wheelbase and a high center of gravity means the bike is far more likely to be at full droop. So the fact that preload affects the way that the suspension starts to move off full droop - and only then - is why it can be used as a motorcycle tuning tool as long as you don’t forget there are other factors involved.
The fact that adjusting the travel range of a two-piece shock also happens to affect preload is why so many people attribute the change in behavior to the wrong measurement. Changes in behavior attributed to preload are almost always due to the change in suspension travel range. As noted in the video, you can change the preload on a spring without affecting ride height, spring rate or compression travel on a car by installing a longer shock shaft, and then car’s behavior will not change unless it was critically short on droop to start with.
All I know is that I didn't preload my coilover springs the first time I installed them and the car was extremely bouncy. After preloading them the ride was much better. As good as it can get with coilovers.
That’s a common line of thinking.
What you really adjusted was your compression travel. To get more preload, you shortened the shock body. This gave you more compression travel so you didn’t hit the bump stops as often. The preload is a side effect of this adjustment, not the cause of the change in behavior.
Quick Question. I brought a Set of Maxpeedingrod coilover for my 2007 infinti G35s Sedan the ride is so stiff when you hit a bump you can here the stuff in the trunk this is fine for a track car etc not for a Daily is there a way that you can soften the ride a bit i think they have preload settings
If the springs are not well matched to the dampers, or if you don't have enough travel, or if the springs are just too stiff, or if your dampers are poorly valved - you will have a poor quality ride. No amount of adjustment on a poorly designed suspension will fix these issues.
Hey Keith, these videos you did are some of the best on UA-cam for suspension stuff! Quick question, could preload become a factor on the inside/unloaded wheels if a light production car is experiencing high levels of load transfer in a corner?
If you completely unload a wheel, the suspension won't start to compress again until it's reached the same load as the preload - ie, if there is 50 lbs of preload on the spring it won't start to compress any further until you have 51 lbs on the wheel. This isn't really a factor unless you've got extremely high levels of preload, as that unloaded wheel isn't really doing much for you. But it's probably why motorcyclists use preload as a tuning tool, as they see much higher levels of weight transfer and weigh less overall.
@@FlyinMiataVideo Thanks man!
The problem I have with your explanation is that the spring, say rated at 100 lbs per inch, if compressed/preloaded 2 inches is storing 200 lbs of restoring force. If a corner of a car weights only 100 lbs (as example), that corner with a 200lbs of spring restoring force will feel over sprung. In a linear spring to compress a spring 2 inches you need to add 2x the lbs/in of what it is rated, not 1x. I have a problem with Ohlins on my M3 in front where spring preload and height adjustment are the same adjuster. I have to preload a soft long spring several inches to achieve the ride height I want. And once you jam several inches of preload into a spring it no longer functions as what it is rated as it functions as x multiple of that and the ride is a bit jarring. I also try to make sure I have enough bump vs droop since the piston shaft is super short, and it requires me to preload the spring quite a bit.
If your preload is higher than your corner weight, then your suspension will be fully extended at your static ride height. This is a real problem, and will lead to unpredictable handling and poor ride quality. In your example, the suspension wouldn't start to compress further until you'd hit a 1g bump. And of course, you'd have zero droop travel. Most of the time, you wouldn't have a functioning suspension at all.
It sounds like your springs are too long in your example. The biggest problem is your short shaft travel, but in order to deal with that you'll need springs that are correctly sized.
About what you say at 8:24, that you adjust the perch to set the ride height. I think this is inaccurate, because in order to get advantage of the full shock travel you would 100% need different spring lengths. So if you have a spring that makes the car sit high, and you want it lower, you adjust the perch lower and then you lose travel - full droop (ie the shaft is not fully extended as the car sits still). On the other hand if you use a short spring and you want to get the car higher, you would then have to get the perch higher up the shock body, leading to reduced compression travel, as the spring colis would bind at some point. So in order for your setup to work, i believe you have to get the springs exactly right for the desired ride height, enabling the shock to full droop and compress. Otherwise you simply get the multi piece coilover result.
That would be partially true if you're reaching the spring's limits - either having it go loose at full droop or reaching coil bind. There's a range in between that allows you to adjust the perch height without having to change the spring. Generally speaking, you want to use the longest spring you can package as that will give you the greatest working range.
Coil bind is a very bad thing and should be avoided at all costs. Since it effectively turns your suspension into a solid piece of steel, it is very hard on suspension components and mounting points. A spring that goes loose at full droop is less of a problem, it simply means you're not making full use of possible travel.
The shaft should never be fully extended when the car is at rest - that means you have no droop travel available at all.
Spring preload is miss used/misunderstood. Preload is used to hold spring in place so if you're airborne from bumps, spring is not flopping. If it is then you've got too short of springs also. And if you end up binding your springs. Should consider adding longer bump stops.
if you have adjustable length coil-overs you can just lengthen the strut body. The length of the strut only becomes a concern when shortening it too much (because you may contact the wheel well under full bump compression).
If you don't have adjustable length coil-overs then yeah... to avoid coil-bind you'll need to either lower the lower spring perch as much as possible (you'll end up lowering the car) or change to a spring with more travel. i would not sacrifice bump travel to prevent bind. Riding on bump stops will not produce a well handling vehicle unless you tune specifically around that intention.
Interesting that the ohlins r&t coils are multipiece. For NA/NB at least. Idk about others.
I have Tein flex Z, which is also a multipiece. Both the Tein's and Ohlins are twin tube dampers, so they have a bit more internal travel compared to most mono tube designs, but they are still a bit short on travel compared to a "single piece" damper. I personally like the lower brackets, and I use them to set ride height, after I adjust the preload/bump/droop ratio the same on the left and right, (with weight in the drivers seat) This is the opposite of what Keith teaches here, and I really don't know which way is "correct". On a single piece, there is no doubt, but on a multi piece, who knows? All I can say is that it worked for me, and many do it the same way. I will have to do a bit more research and head scratching :)
Need a video for , "do i need more or less dampening?" For knowing how to adjust for different conditions. I have the fox coilovers with the standard spring rates on an nb2 and use for street and track use
Noted! I've added your suggestion to our list.
@@FlyinMiataVideo you guys rock!!
Hello from sweden! I have the standard v-maxx coilovers for NB. I bought them before I knew about the existence of a FM version.
I have not installed them yet, Is there someone exchangeable parts that I should buy from you to modify them to FM spec?
The biggest difference is our custom springs on our FM V-Maxx set-ups. You can get those separately from our site, but this will void your TUV certification.
Great discussion sir, my confusion. 5mm preload will react the same as 40mm preload, once the car is on load. Correct?
Does 40mm preload will tend to get coil-bind more compare to 5mm preload. Cause of 40mm preload has less shaft travel. Is it correct?
What are the pro & con of using low preload & high preload.
Mine currently set to 30mm preload, and I have noticed coil-bind mark on the lowest ring of the coil. Appreciate your replies.
You're using preload as a measurement of something else. I'm guessing you're equating it to the adjusted length of a two-piece shock, as preload itself has no effect on the amount of shaft travel.
Coil bind happens when the spring runs out of travel before the shock does. There are a number of factors involved in the geometry, but if you are experiencing coil bind you need to deal with it. The correct solution is to go to a longer spring but packaging doesn't always allow that. If you can't increase the amount of travel in the spring, then you have to limit the amount of travel in the shock or lower the car.
Pro and con of high preload? Watch the video. It's not a thing. Again, you're equating "preload" with something else, probably shock geometry.
If you only have marks on the lowest coil, you're not putting the spring into full bind. The little half-coil at the top and the bottom of the spring will always close up first.
@@FlyinMiataVideo in that case I'm going to reset my preload to a "normal" position and test how the feel of the ride. Still wondering why the guy that tune it put so much preload on my coils, Thanks.
@@JTNaise It's not preload. Set the shock geometry so you get the range of travel you need. Then you set the perch height so you get the ride height you need. Don't think of it as setting preload.
Would spring pre-load affect the ride quality in terms of how crashy it is? On my 2005 R53 Mini, I have BC Coilovers (fitted by previous owner) and they are horrenoudously crashy - any kind of broken road surface or slightly sunken grids in the road will make the suspension crash and bang - the whole car shakes and rattles, for a road car it is pretty much unacceptable and embarassing when having passengers in the car. I have been told that this could be due to the BC using a pillowball top mount (metal to metal) with no rubber bush - but I have friends who have different coilovers which are also pillowball that dont have this crashyness?
I know the BC BR series are quite an expensive coilover, so I am kinda surprised at how no one else seems to comment about this.
I've played with the damping settings (full soft to full hard) and it didnt really affect what I am experiencing.
Any help much appreciated, thanks!
It shouldn't have an effect until you get your preload close to the weight on the wheel - in other words, once the suspension doesn't really extend when you jack a wheel off the ground. It's a little difficult to identify exactly what's going on from your description, but we'd start by making sure you currently have enough bump travel. If they're a particularly short travel setup, leave yourself some droop travel as well - you'll want a roughly 2:1 ratio of compression to droop. Given that you've already played with damping settings, it's most likely a geometry problem with the setup. Get yourself the setup instructions for your coilovers and start from scratch.
The pillowball mount might transmit some extra noise, but it shouldn't degrade actual ride quality. Bad end links can also cause noise but not shakes.
Wow, I now understand this. Not that hard. Thanks
I need maximum travel when I take my Miata in the woods.
Also, any time you drive it on public streets and any time you hammer a curb hard on the racetrack! Suspension has to have room to work or it doesn't work.
@@FlyinMiataVideo As Ian Tyrrell says (check his channel, top chap) suspension has to suspend.
Perfect analysis, thank you! Just a question: In a rear torsion beam of a FWD car where damper and spring work separately (not as a coilover), if you use spring spacers in order to raise the ride height at the back, do you affect the spring preload?
Yes, most likely. The shock will likely be the limiting factor at full droop, and thanks to the spacer the spring won't be able to extend quite as far. So the preload will increase.
Will this have any effect on the behavior of the suspension at anything less than full droop? No, not unless the spacer is so big as to put the spring into bind at full bump.
@@FlyinMiataVideo Thank you for your reply! The preload changes the force needed to start compressing the shock, correct? So why this will not have any effect on the behavior of the suspension? I would assume that at least for "small" forces a preloaded spring will be "harder" to compress and therefore harder compress the shock.
@@dinostalieris3998 When the suspension is at full droop, it won't start moving again until the loads on the spring exceed the preload. Once the spring starts to compress, it won't matter if there's any preload or not. So the only time there is any effect is when a wheel is fully unloaded, such as when you're jumping or if you're hanging a rear wheel under hard cornering - something FWD cars may do.
so the tein flex z will be worse than street advance z?
What impact on the length of travel as pertained to twin tube vs. internal floating piston monotube design, and how that impacts the actual performance. Thanks.
For ultimate street ride quality, comparing multipiece coilovers, can a twin tube outperform a monotube because of longer shaft length, ie. longer travel?
It's possible that internal design might affect the amount of shaft travel available for a given shock body size. So mono vs twin tube isn't really a factor, it's just about internal packaging. Twin tubes tend to have valves at the foot of the shock as well so I'm not sure there's necessarily an inherent difference.
Where you're going to see street quality differences is in that high internal pressure with a monotube - but the valving is a lot more important than the tech used.
@@FlyinMiataVideo Thanks. i get that "preload" is an unfortunate and misleading misnomer with respect to coilover, but.... Isn't the 2 piece design in reality allowing you to set the piston height, to determine how much up travel vs. down travel you might choose ,while allowing you to independently get a specific ride height ( aka why u called the universal). Isn't the one piece design based on making to a specific application, but you are thus dictating a narrower range of ride height parameter( which you have tested to give best outcome?). How much up travel to down travel do you want on the FOX set-up. If you adjust the spring perch, aren't you thus changing the piston position...i guess if it never bottoms or tops out, the you are OK. Also, wouldn't going to a reservoir shock give you more packaging room to get even more travel for a given entire shock length, but you don't need that because the one piece has sufficient travel, and keeps cost, complexity down, or not? Thanks, your video is much appreciated.
@@drtone You're right, being able to adjust the length of the shock means you can trade off bump travel for droop travel and vice versa. That sounds like a great ability - until you realize that the correct setting for Miata bump travel is "as much as possible". Unless you're building a lifted offroad Miata with 29" tires, you want as much bump travel as you can possibly package. So any trading of bump for droop is a bad trade. That's what the fixed length shocks are built around - if you are using your Miata as a Miata, a performance road or track car - then you need all of that bump so the only correct length for the shock is to allow for that full travel. Once your shock length is set, then you set the ride height with spring rate and length and perch position.
A remote reservoir is mostly used to increase fluid capacity of the shock or to allow double adjustability of a monotube design. It may or may not provide a little more shaft travel, but at a fair cost and with some real packaging difficulties.
Make sure you know your motion ratios. The fronts tend to be very high relative to your rears.
A 6in travel Front suspension could be 10in travel at the Front wheels.
Good point and for NAs this is why a 3/16" shock top spacer results in a 3/8" height difference at the wheel.
i have fully threaded coilovers and i dont know how to soften the ride its very stiff and unconfortable... pls help
Most fully adjustable coilovers have some sort of damper adjustment knob on the very top of the shock shaft, or near the body on the shock body, but not all coilovers have that capability. Spring rates can also make a huge difference on ride quality, so if your springs are too stiff, your ride may be very harsh, even with the shocks adjusted to the softest setting. If you can, reach out to our customer support team directly via phone or email. They can get some more details on your specific setup and possibly give you some pointers on how to get a better ride.
Wouldn’t adjusting the spring affect the shocks range of usable mostion ? Put the spring too high can’t use all the shock spring too low shocks compressed
That’s one way to look at it. Just remember that there are other limitations to the useable shock motion, such as the control arms making contact with the subframe or tires hitting sheet metal.
Coil overs, where does the long one get installed front or rear of car.?
In the case of the NA/NB Miata, the long shock goes in the front. Just look at the stock ones if you forget.
Great Video, but now I am a little bit confused. I have a 2 piece Coilover made by Tein. I always thought I adjust ride height by breaking the lower collar loose and spinning the whole Assembly. Now you told me ride height is adjusted by the perch location? I know both affect ride height but how should I adjust it best ?
Set the shock length so you get full compression travel. Then set the ride height using the perch height.
The end.
@@FlyinMiataVideo so set the Shock lenght as short as possible, just watched the Video Again and you also covored my question in the Video, thanks anyway That you answered my question.
@@FlyinMiataVideo is that an mx5 specific reccomendation or could that theory be carried over to a double wishbone Honda? I've read other articles which suggest using a bump droop ratio of 2/3 bump to 1/3 droop and setting the shock body to that point (and then using the springperch for ride height as you suggested). Obviously your suggestion of just setting the shock body to maximum available compression travel is easier than calculating that ratio etc - and hence preferable to an idiot like me!
Many thanks!
What coilovers for the na, are good for preformance?
We have a selection of options that we've tested and can recommend. The right one depends on your budget, your goals and your use. It's probably best to give us a call or email us so we can give you good advice.
Great video, but I still can't adjust my Tein Flex Z for my 2009 Acura Tsx! I dont understand the instructions and one of my spring could move freely after doing some adjustments. I still dont understand what's preload and how my spring should be compressed before installing it on the car! X) more preload will stiffen my suspension? Or it's just marketing and I can install my coilovers with the coil moving freely in the assembly, no preload? Thanks...
More preload will NOT stiffen your suspension. That's a fairly common misunderstanding and one we'd hoped we'd addressed here. You only need enough load on the spring to keep it from flopping around at full extension, although the geometry of the rest of your suspension may demand something different. Can't help with Teins for an Acura specifically, unfortunately.
He literally covers all of this in the video. There's no way you actually watched it.
@@opmike343 i called tein and they told me how to set my suspension.
Keith, there is an important way in which pre-load affects handling. This occurs because preload directly impacts the amount of free travel before the shock top starts to compress the bump stop. This gap is controlled very directly by the preload adjustment on the coil spring. The higher the pre-load the bigger the gap.
As has been discussed on the Forums in detail, a Miata in a corner rides with the two outside bump stops in direct contact with the top of the shock. When bump-stop-to-shock compression occurs the net-effective spring rate becomes that of the coil spring plus the spring rate of the bump stop itself. The length of the gap between the top of the shock with the car at rest, and the bottom of the bump stop, determines just how rapidly bump stop engagement occurs during the entrance to a corner. When the bump stop is engaged the net effective spring rate becomes non-linear and increases quickly under load.
Changing the coil spring pre-load in order to adjust chassis ride height changes the bump stop gap. The more pre-load the bigger the gap. If there is not enough gap, suspension travel down from the neutral position becomes very limited. In the words of Colin Chapman: "Any suspension will work, if you don't let it." It does not matter how much stroke the shock has if the bump stop interferes with your access to it.
I have all of your books, Keith, and they are excellent. They are the 'go-to' texts for Miata tuning. This said, bump stop clearance is a neglected topic in Miata suspension tuning. The task of setting bump stop clearances is worthy of a separate video or a chapter in a book. Shock pre-load settings directly affect bump-stop clearance. Bump-stop clearance determines the point at which the bump stop engages. There is no point in having long shock travel if your bump stop blocks your access to that travel during compression.
In setting up shocks, once you have set the pre-load to obtain the bump stop gap that works for your car, then you need to reach to some other method for setting the front to rear chassis inclination. For this I used a the stainless steel FM shock mount spacers. On my suspension I had to shim with FM spacers. Also to get the gap I wanted I had to use a shorter (stiffer) bump stop in front. I now have a ride height, chassis inclination, and bump stop gap that is optimized for the way I use the car. The bump stops engage neither too soon, nor too late, and I can use all the available shock travel.
That's the common misperception I was trying to address.
There is only one correct setting for the length of the shock on a Miata. Any other length will take away compression travel (bad) or fail to engage your bumpstops before your suspension binds (also bad).
One-piece shocks will already be this length. Two-piece shocks have to be adjusted to this length. Any other length will be incorrect.
Changing the coil spring preload to affect chassis height does not change the position at which the bumpstop engages relative to the chassis. That last bit is the important part. You will retain as much bump travel as the car can manage. It changes how much travel there is between static ride height and that engagement - but since the ideal engagement point is determined by the rest of the suspension geometry that doesn't matter. That ideal shock body length is the same regardless of your static ride height. Note that I am assuming we're talking about Miata designed to be used on paved surfaces, the rules are different for rock crawlers where droop is more important than bump.
Where people get confused is what you're using for a baseline. Looking at bump travel relative to static ride height versus looking at it relative to the chassis baseline can get you tangled up. If you're only looking at bump travel relative to static ride height, you forget that there are other limits imposed by the chassis and that you cannot simply lower the car and get more bump travel - not unless you had it artificially limited in the first place.
In your case, the combination of "extra" travel from a super-short shock body and a spacer on top of the upper shock mount cancel each other out. The short shock body is limiting total wheel travel - if you have maximum bump, you are loosing droop. If you decide you want more droop, the only way to get it is to decrease your bump travel. This tradeoff is pitched as a feature, but really it's a limitation.
@@FlyinMiataVideo All well and good Keith. Consider, if you will the following events which occur as you adjust the pre-load on a coil over. You have done this many times yourself I am sure. I have done this many times as well.
Start with these parts from FM's inventory. 1. Koni sport shocks. 2. Bump stops of the type you sell, and 3. Ground Control adjustable perches for the Koni shock. Install the shock, bump stop and perch in the car with the spring loose. Put the weight of the car on the shock. At this point the weight of the car is carried only through the bump stop compressed against the top of the shock. Initially there is no load in the spring. The spring is loose on the perch.
As you tighten the nut on the loose spring, and the spring starts to compress, the compressed bump stop starts to lengthen as the spring takes the load. As you continue to tighten, a gap between the bump stop and the shock top emerges as the load transfers to the spring. At the point at which a gap emerges all the weight is carried through the spring to the perch. As you continue to tighten the spring the gap between the top of the shock and the bump stop gets bigger. This is simply 'what happens' in your shop and in mine.
My personal experience is that gap between bump stop and shock is very important. It is one of the more important dimensions on the suspension. As you say there are many misconceptions about this.
If the gap between bump stop and shock top is too narrow the car is hits the bump stop too frequently and the ride is unnecessarily harsh, and the travel is limited. When the gap is too wide, the car rolls on to the outer bump stops late as your enter the corner.
This is a practical example from your shop and mine of how a change in the pre-load affects handling.
Here is a final paper example. With the same 2,000 pound car and an 8" long 250#/in spring and the corner supported by a jack, dial the perch nut up against the spring until contact is made. Dial the perch nut 2.125 inches further. There is now 531# of preload. The pre-load is 31 pounds greater than the corner weight.
Start to lower the jack, placing the corner load on the spring. There will be no further compression of the spring. The spring is pre-compressed 2.125 inches, by the perch for 531# of preload. The weight of the corner is 500#. The preload is greater than the corner weight. The system in in balance. There is no motion. The corner sits 2" higher than the example with no preload, and 1" higher than the example with 250# of preload. The gap under the bump stop is 2" larger than the example with no preload.
In each of examples the preload regulates the gap between bump stop and the top of the shock. My practical experience is that this is simply the way that you, I and everybody else who cares about this regulates that gap if they have a preload adjustable shock. The weight of the chassis corner has to overcome the preload in the spring before it compresses the spring further.
When there is no preload, only the spring rate is important. When the preload exceeds the weight of the corner there is no compression of the spring by the weight of the car, and the spring rate is unimportant. When preload is in the middle, both the preload and the spring rate regulate the height of the car, and that controls bump stop gap.
There are other dynamic effects, but this is the semi-static balance of forces that determine ride height, and in a suspension in which only the perch height can be adjusted that sets bump stop gap.
@@FlyinMiataVideo Keith you write, above: "In your case, the combination of "extra" travel from a super-short shock body and a spacer on top of the upper shock mount cancel each other out". This is not correct. My case is a Koni Sport or equivalent which is not a short shock. On page 113 of my edition of "How to Build a High-Perfomance Miata", you write, under the topic Spring Preload, "the only thing that our pre-load has done is lift the car." This is correct that the car lifts when pre-load is increased. However this is not the 'only' thing that happens. Consider the consequence in terms of bump stop gap. Lifting or lowering the car changes the bump stop gap. And that gap is a rather sensitive dimension.
There are three targets you are trying to hit in adjusting preload. To first order, you have only one knob to achieve that. The first goal is that the shock needs to be in the approximate center of available stroke with the car at rest. The second goal is that the ride height has to be high enough that the roll center is reasonably close to the center of mass. And thirdly, the bump stop gap needs to be large enough to permit full use of the shock travel in compression, without approaching coil bind. The one knob that you have to hit all three goals is the pre-load nut. You can also change the length of the bump stops. You can use different length bump stops front and rear. Finally you can shim the top of the shock.
When I install shocks, I set the pre-load such the shock is approximately in the middle of the available range of travel. This is one of the more important settings. It is also the easiest target to hit.
After that I swap out bump stops of different lengths and stiffnesses to get the approximate gap I want.
When you lift the car by increasing pre-load, the bump stop, which is attached the chassis, and the upper surface of the shock, which is attached to the control arm, move apart. A small increase in pre-load increases bump stop gap meaningfully. As you tighten the preload nut, with the wheel off, and the control arm supported by a jack, you can measure the change in the gap between shock top and bump stop as that gap opens up.
At this point I look at the static height of the chassis. If everything else is the way I want it, I shim to get the chassis inclination I want. Shimming, does not cancel out anything as you suggest above.\ The load into the coil over is not changed by the shim. The compression of the coil-over does not change. The only thing that happens is that the end of the car that is shimmed lifts slightly. On our cars the factory set up has the rear a little higher than the front. Inserting the FM spacer in the rear increases the ride height in back slightly, or brings up the front if that is what needs to be done.
Since a Miata rides directly on its outside bump stops in a turn, the point in the entrance to the turn at which those bump stops make contact is regulated by gap under the bump stop. This is directly affected by the pre-load. I find that this interdependence of the two is not commonly understood. A change in preload affects handling by affecting one of the more critical dimension in the suspension, the gap, or free movement of the shock before the bump stop engages. This gap determines how much chassis roll has to occur before the chassis settles onto its outside bump stops in a corner.
Getting compressive shock travel balanced with droop travel is important. At rest the shock top need to be in the approximate center of stroke. Getting the timing of the engagement of the bump stop is at least as important. Hitting the end of travel in droop is infrequent. Rolling over on the outside bump stops occurs continuously through every corner taken at speed. Changing the preload changes the gap. In any treatment of preload these other elements need to be considered. Preload does affect handling by changing how early or late in the corner the chassis settles down on the outside bump stops, front and rear. This is fundamental physics.
I frequently see cars where the bump stop gap has been closed up by lowering the car through a reduction in pre-load. When this is done it doesn't matter how many thousand dollars you paid for your coil overs. They have no travel in compression. Those expensive coil overs are doing little that is useful. You could replace them with a piece of oak and the car would handle as well. Preload matters because it affects bump stop clearance.
@@maneki9neko I think the big disconnect between us is that you believe that you want bumpstop engagement at some specific point in the travel, where I want to delay it as long as possible. You want a specific gap, I want as big a gap as you can get. I want the car riding on the springs, not the bumpstops, because that's when the suspension is actually able to move. Years of testing have shown that as you increase compression travel (the distance between the top of the shock and the bumpstop), the car rides better and handles more consistently. When the car is on the bumpstops, the suspension stops moving and you lose the ability to absorb any further pavement imperfections. A big bump will mean a spike in spring rate as you slam into the stops, and that leads unpredictable handling.
Here's how I set up a suspension: set the shock length and upper perch design so the bumpstop engages as late as possible. There are limits to when this can be, imposed by the geometry of the suspension. A one-piece shock that's properly designed will already be at this length. A two-piece shock with "adjustable preload" has to be set at this length. If you make the shock any longer, you will hit the bumpstops too soon and your ride quality, handling and ability to absorb bumps will be compromised. So there's only one correct length for the shock. This means an adjustable body shock can be adjusted one way, and that's to match the length of a well-designed non-adjustable body. Anything else will compromise the car.
Now that you have maximum bump travel, you can move on to ride height and corner balancing and the rest of setup. You need a spring rate that's stiff enough to keep you off the bumpstops at your chosen ride height, but that's the case regardless of if you can adjust shock length or not.
Droop travel is not as important as bump travel to a performance Miata, but if you want droop travel the best way to get that is to package the longest shaft possible in the shock. On a one-piece shock, you have more room for this shaft. So your one-piece, "non-adjustable" shock will have maximum compression travel and more droop travel than a two-piece shock. You can see this illustrated clearly in the video. Setting your shock so that it sits in the middle of the travel is not a good way to start your setup, because you will probably give up that critical compression travel for droop.
Of course, there are edge cases. Having preload that is equal or greater to the corner weight as measured at the shock (not the wheel) means there is zero droop travel. This is a failure in the design of your suspension, not a setup problem. It's very difficult to get into this situation, but I have seen it on a Miata with a very, very short travel shock. Obviously the car did not work well at all. You can't manage it with parts sold by Flyin' Miata unless you combine them in a way that was not intended. If you run a very, very high ride height you may find yourself getting into this situation as well.
Spec Miatas should not always be taken as the correct way to do things, as they are given some very specific limitations on components by the rule set and builders have to do the best they can with those components. And even then, there have been changes in that rule set specifically designed to allow for more movement before the bumpstop is engaged.
For any given shock, does the droop travel depend on how low your ride height and how high your spring rate is? It seems to me that is the case, as your car sits lower, the shocks will be compressed more at ride height so there will be more droop (less compression travel). On the other hand, if the spring rate is higher for any given ride height, the shocks will compress less and therefore take away some droop travel (but increase compression travel). This seems to make sense to me but I am not sure. So is it always a compromise between droop/compression travel and ride height/spring rates?
That's half right.
Ride height is definitely involved in the amount of compression vs droop travel available for a given shock. It's the primary factor.
Spring rate itself won't change the amount of travel. It's all about ride height and the shock geometry. If you increase the spring rate but want to keep the ride height the same, you have to change some other geometry such as the perch position (this has no effect on travel ranges) or the length of the shock body, which can have a considerable effect on shock travel range. The shocks on a Miata should be set to give as much compression travel as the suspension will allow, so there's really only one correct shock length regardless of ride height unless it's some offroad lifted mutant or you have a shock that is poorly designed and extremely limited in shaft travel.
@@FlyinMiataVideo Thanks!
How do you pre load a coilover with a helper spring?
We don't prefer multipiece coilovers that would require that adjustment. Sorry.
What if your springs are too short
Preload would make a difference when working with a progressive rate spring correct?
It would not. The amount of force being put into the spring is exactly the same regardless of the preload at full droop.
@@FlyinMiataVideo I had a car with double progressive, tapered spring and one of my cars uses a progressive variable diameter and in both cases the amount of spring preload could change the initial crack(movement) of the spring. In the latter case it needs to run quite a bit of preload to get the ride height I need. A lot of people ran these lower as it was simply more comfortable but bump steer could emerge. This was because there wasnt a lot of droop in the shock body before topping out. If I get these rebuilt I will get the shaft modified. This is an old ohlins japan coil over and made to suit their roads, they dont have a lot of bumps, good surface and is pretty old tech by todays standards but the valving is ok. it just doesnt work anywhere else
The other example is a rally length shock but with less spring preload to run more of a street car set up. While comfortable enough on the street the lack of preload made the chassis transfer weight more then I liked. It wasnt as linear as it should have been. Exiting a corner on the track it would squat and unload the front causing understeer (awd car) and really needed a linear spring in the back. I never used this car for track it was a street car that I took due to my track car being undrivable.
Preload does not change spring rate but will change dynamic chassis attitude as it goes through its travel in the case of progressive springs. It will also change the range, so if you have a 7-10kg/mm spring adding preload might make it 7.5kg-10kgmm in an extreme example. Rate hasnt change but the effective working range has and you will feel it different in the drivers seat.
Of course linear springs eliminate that problem which is why not a lot of aftermarket companies use them. As you can see, they are harder to set up
Also the vmaxx you said you lengthened the springs. Can I still go low if I want to?
You can go low. Can you slam it to the point of uselessness where you're dragging the oil pan? Not so much. At that point, just take the springs off.
I didn't mean that low I just don't want much gap left. I have very good roads here in north Georgia mountains. Do you know when the classics will be back in stock? Thanks for the reply!!
tommy dvorak you might want to do ALOT of research on the forums, specifically the suspension threads. There you will find pictures of miatas with different suspension set ups along with reviews. But if you are just now learning, you might want to try the FM VMAX coil overs which can bring you very low or very stock and are comfortable/ better than stock. It’s a starting point, once you learn more, you can gauge what you want a little better.
www.miata.net
www.clubroadster.net
www.mazdaroadster.net
So how do you lower a single body coilover? I just loosen it down and let the shock go down on its own? Wouldn't it be bad for the coilover to always bottom out?
That's what bumpstops are for, taking the hit when you run out of travel. And a properly designed single body coilover has a shock length that will bottom out just about the time the suspension binds up, so a two-piece wouldn't be able to offer any extra bump travel past that point. This last piece is one that is often overlooked. There are limits to how much bump travel is available.
@@FlyinMiataVideo i see, so bumbstops plus a helper spring are need if i intend to lower my car on a single body coilover? Sorry it's my first time using a single body coilover and was wondering how I can lower it without compromising the shocks.
quick question... Is the additional 4 mm on preload required and or a must… On factory bought proper OEM spec coil overs for an every day driver… Meaning 7:36 once a spring is tight in the cradle do you really need that additional four or am I just hindering ride quality?? thank you for a response
Preload does not affect ride quality. Not sure where the "required" 4mm of preload came from, but that may be a manufacturer making sure various hardware does not come loose. Set the shock length first (if applicable), then set the ride height with the perches.
@@FlyinMiataVideo Thank you for your response👍
@darksolara6750 You are welcome and thank you for watching!
I am curious with do harder the spring rate is the less travel it need? For example a stock 5k spring and have 10mm droop travel, it’s that mean a 10k spring only need 5mm droop travel? It’s that how it work?
We usually think of it the other way around. How much spring rate do you need given the travel available. But you can look at it this way.
A 5k spring will compress twice as far as a 10k spring for the same load. So you need twice as much travel available if you want to stay off the bumpstops. And we're paying more attention to compression travel than droop travel.
@@FlyinMiataVideo thx for your reply
@@FlyinMiataVideo I just clear my mind. Just make sure my assumption is correct. Droop travel don’t affect by the spring rate a lot because it’s not compress the spring, bump travel does.
Ride height will not be the same if there is pre load on the spring. Öhlins have coilovers where height and pre load are intertwined, like me e46 M3. By dialing in pre load, you’re reducing the amount that she suspension will compress when car is static
The ride height is determined by the distance between the upper and lower perches, the spring rate, the spring length and the weight on the springs. That's it. Preload doesn't change that - but changing the perch height can change the preload, which is why people get it mixed up so much.
@@FlyinMiataVideo if you’re only changing the bottom spring perch height, effectively increasing pre load, how can you explain that the car height increases? You’re not changing the overall position of the spring, solely the bottom part.
It would make since if the whole spring was higher, which it isn’t.
@@DriftingSquirrel The spring sits on that bottom perch, the car sits on the spring. You move the perch up, the car has to move up. The spring will be the same length for a given load, so you can consider it a fixed length.
Preload can only be measured with the suspension fully extended, because that's exactly what it is - the amount of load on the spring with the shock extended. Once the force on the spring exceeds the preload, the spring will compress - BUT IT DOESN'T COMPRESS DIFFERENTLY BECAUSE OF THE PRELOAD. That's important and it's where many people get tripped up, they think the spring somehow "remembers" what happens at full extension. It doesn't. If a spring has a 400 lb/in spring rate and 400 lbs of load, it will compress 1" from its free length. It doesn't matter if it has 50 lbs of preload or 75 lbs or 0, it will be compressed by 1" with that 400 lb load. And that's what will determine the ride height.
When your preload exceeds the corner load - if we had 600 lbs of preload on that example - then your spring does not compress until you hit a big bump and you have zero available droop. I've seen cars set up this way by people who don't know what they're doing, it's not functional. But it is possible to do.
@@FlyinMiataVideo The spring sits on the bottom perch - that did it for me. Very well, I have understood the logic, and I'm thankful that you've taken the time to explain everything properly to me. Most other people (channels) would've sent me on a hike right about now.
I do have another question however: you say that if the pre load exceeds the cornar load, then the spring will not compress. But, if the spring will compress the same amount (given by the spring rate) regardless of the pre load, how does this work like that?
I don't know if this is a semantic thing in the example presented, but the bit I'm still confused about (and other comments only added to the confusion) is the mention that "the ride height will be the same" around 2:35. When people talk about "applying preload" aren't they doing so by raising the spring perch while the shock is at full extension, which I've understood should be raising ride height? Or are we assuming that they'd somehow be adjusting preload without raising the spring perch in that example?
Edit: never mind, I found an argument below that suggests we agree that the ride height will change if you "adjust preload" by moving the spring perch up. It seems like your main contention is that the preload is a side-effect there and not the main thing we're adjusting, but it seems a tad nitpicky to make that the distinction since the only way I could imagine anyone out there reasonably changing the preload IS by moving the perch at full extension-- I feel like that is the basis of a lot of the misunderstanding/disagreement in this comment section.
The point being made there is that preload is only measured with the shock at full extension. It does not directly affect ride height. It's possible to build two shocks with different shaft lengths but that are otherwise identical. One will have more preload than the other with the perches at the same place, but they'll have identical ride height and travel. This isn't something you can do without disassembling the shock, so it's more of a thought exercise for most people.
With two piece shocks, it's possible to change the perch position - change the preload - and then adjust the shock body length so that the ride height stays the same. This is where all the confusion comes from, the concept that changing the preload is changing the handling or ride quality. This sort of adjustment has the side effect of changing the range of travel in the shock, which is what people are really reacting to.
@@FlyinMiataVideo Makes sense, thanks for clarifying!
How do MeisterR compared to yours?
We generally don't comment on other brands, as we don't know them well enough. Conversely, we've found that comments from other vendors on our parts are usually inaccurate.
That said, if the MeisterR coilovers are two-piece bodies, they share the same attributes of all two-piece shock implementations.
Doesn’t a 250lb/in spring mean that if you preload 2 inches the initial 500lbs of force go straight to the chassis with no damping and absorption by the shock?
No, because there's already the weight of the car on the spring. You're not starting from 0 unless you're jumping the car. This is a common oversight.
There is an edge case where your preload is higher than the cornerweight of the car. It this happens, there are some fundamental problems with the specification if your suspension. It's possible to get it that wrong - we've seen it a few times - but it's only possible if the springs are far too long or if the shock has minimal droop travel.
Flyin' Miata so if I jump or lift a wheel a lot while say hitting gutters or rumble strips it could be an issue?
@@monkeypainter808 It's not a black and white line. Lifting a wheel is a sign of not enough travel for your intended use. If you are jumping a lot, you'll probably set up your suspension differently including valving differences. Our friends at Paco Motorsports have probably done more work on off-road Miatas than anyone else.
500 lbs of preload is pretty extreme. In reality, it's not liable to be more than maybe 10-20% of your corner weight. 500 lbs is more like 80%.
Why is preload important in bike suspension setup?
Probably because bikes are more likely to completely unload their suspension, which is the only time preload becomes a factor in how the suspension moves. In that situation, the preload affects much load is required on the suspension before it starts moving again - but once it starts moving, preload is no longer a factor. Cars very rarely lift wheels off the ground.
It's also possible that it's poorly misunderstood in the bike world like it is with cars, and that people are confusing preload with other factors such as range of motion or static ride height.
Drooping a coilover to slam ride height low, destroys the shock...Correct?
I don't believe so. I think where that story comes from is the fact that dropping too low means too much time on the bumpstops, and the shock does not have the damping to control the high spring rate they have. So it acts severely underdamped which means it acts like a blown shock.
Now, taking bumpstops out and allowing a shock to bottom out internally - THAT can damage a shock.
@@FlyinMiataVideo Thanks for your time.
I need less then an inch of droop to get the ride height I want. After maxing out coilovers & using shorter strut forks....Still not low enough with out drooping the spring a lil.
I just got adjustable dampners. I'm assuming Ill start with full hard then click my way softer...
@@Cliffjumper We recommend starting soft and increasing the damping. It's a lot easier to tell when you get it right.
Droop is useful both for dealing with things like driveways and when going over crests at speed. Less than an inch is not enough.
Ofcourse its shorter ! if you want your car Lower you have to use the coilover version of you want the option to raise or lower your car when ever you want but its alsow harder or adjustable in hardnes so it dosent mather if its shorter , you can use a singlepiece but then you have to use a shorter spring but then you cant adjust anything more
How low on an na can you go with the fox???
Buy it and find out lol 😆
As low as you can with any suspension. The limitation is the tradeoff between spring rate and travel. If you run a lot of spring, you can run very low - we do that on our track cars. But if you're going to run street rates, you need to set the car taller so you're not on the bumpstops all the time. This is true of any suspension.
the preload isnt for that . its for the travel that it has when u ride over a pot hole for example. if you have preload on it the strut will travel faster or slower downward .
It doesn't work like that - the spring rate is unchanged.
The only time there is a difference is when the spring is loose at full droop, at that point the shock will stop extending when the spring is fully extended. But once you get past that, it doesn't matter how much preload there is at full droop, the shock will extend in exactly the same way and at the same speed.
How can you set the required preload to keep the system stationary?
Not sure I follow the question. It’s all about the weight of the car on the springs at rest. Preload does not change spring rate, it’s only a measure of how compressed the spring is when the shock is fully extended.
@@FlyinMiataVideo Hi thank you for the reply, sorry, let me rephrase the question. how would you check or calculate preload in spring to keep the corner(say left) stationary if the cornering load is say 300kg?
apologies, If you have already covered something like this in another video. sincerely Ash
@@wheelskawasakileicester1146 What do you mean by "keep the corner stationary"? You don't really want it stationary, that means your suspension is locked. Do you mean minimal roll? Do you mean you want the shock fully extended with 300 kg of load on that corner, so it takes more than 300 kg of load for the wheel to start moving?
@@FlyinMiataVideo Hi, I mean "shock fully extended with 300 kg of load on that corner, so it takes more than 300 kg of load for the wheel to start moving" yes.
@@wheelskawasakileicester1146 Well, in this particular case you'd probably have the suspension fully extended at static ride height. That's not a good idea, as the car will have zero droop available and will easily hang a wheel in the air. We've seen it done on high-dollar Miata suspension setups with insufficient shaft travel, but the cars don't actually work very well.
The math is easy, though. Take a spring with a 7.5kg/mm spring rate and a 200 mm free length. If you want 300 kg of preload (in other words, the spring will not compress further until it has more than 300 kg of load on it), that's 300/7.5. The result is 40mm, so you'll look to put your perches 160mm apart at full extension.
On a car, this isn't really a way to do suspension tuning. It may be different on motorcycles which see dramatically higher shifts in load and are expected to lift wheels on a regular basis. We can't really achieve 100% weight transfer under acceleration in anything but a dedicated drag car.
Defuq is he talking about spring preload tuning is a thing. Just not in that context. It usually used for corner balancing.
You’re confusing cause and effect. You’re not adjusting preload when you’re corner balancing, you’re adjusting perch position. The change in preload is an irrelevant side effect.
Don't you need to be able to limit compression travel in order to prevent the tyre from crashing into the fender before the shock reaches full compression? Not a case of 'we want as much travel as possible.' single piece coilovers don't allow for this adjustment unless they are designed specifically with this in mind and are to be used with a specific wheel size and nothing else.
If you are running a wheel/tire combo with a significant difference in overall diameter, you will need to limit compression travel to avoid interference. This is fairly rare in the Miata world other than for lifted cars, but it can happen. It's why we include bumpstop spacers with our ND Fox suspension as some of the wider sizes are taller.
But that's an unusual case. It's far more common to retain the same tire OD. Note that wheel OD is not a factor - it's all about the tire. So the suspension is designed to work with a tire diameter that is similar to stock, such as a 225/45-15 in place of the original 185/60-14 used on an NA Miata.
When we say you want as much travel as possible, that is "as much travel as possible before you reach a limit imposed by your components". You do not want your shock preventing from using you all of that potential travel.
First step to suspension tuning: Add lightness.
I sure wish you guys had a video on the MSM, and modding steps. I was surprised not to find anything on the MSM in your videos.
Hypothetically, if preloaded 1” on a 400lb spring. I would beed 800lbs to compress it 2”. Which would be a harsher ride if I didn’t have that 1” (400lbs) being used already.
Not arguing. Trying to better understand.
That's the common misconception, that somehow the preload gets added to the spring rate. That spring will require 800 lbs to compress a total of 2" even if there's no preload. That's what the spring rate of 400 lbs/inch means.
In your example, as soon as that preloaded spring has 400 lbs on it, it will start to compress further. By the time you've put 800 lbs on it, it will have compressed 2" from the free length - just as if it didn't have any preload at all. You don't add 400 + 800 lbs = 3" of spring compression. Once your load on the spring has exceeded the preload, the preload effectively ceases to exist.
That's where the preload can have an effect, if there is less load on the spring than the preload - which means your suspension doesn't compress at all when the car is at rest. Obviously that's not a good situation. You need fairly significant levels of preload before this becomes a factor, or you need massive amounts of weight transfer as on a motorcycle. There are some edge cases that can start to cause problems as you get close to them but if you get there you have more fundamental problems.
@@FlyinMiataVideo thanks for taking the time. I had a set of Bilstein B14 (progressive) that wouldn’t go high enough. I added as much spring perch as I could and the ride quality suffered. Im think I used up all the soft portion and was maybe into coil bind.
Bmw btw.
@@jpwilliams5264 That can certainly happen. Coil bind feels okay until you get to a certain point in the travel, and then the suspension feels as if it goes solid. BANG! Progressives are just weird overall.
His spring preload explanation is off. Spring pre-load....is not for adjusting ride height....but suspension SAG. If you want your shock piston to only be 25% down into it's stroke when you rest the cars weight on it, but the shock actually compresses 40% of its total travel,...... then and only then.....you use spring preload to compress the spring and move the shock back up into it's stroke until that 25% number (or whatever you are shooting for) is reached. If the shock doesn't move down that 25% you are looking for, you can either A. Get softer springs, B. use 2 springs (a softer one for initial travel) or C. (last resort ASSUMING YOU STILL HAVE SPRING TENSION AT FULL EXTENSION AND NO BIND AT FULLY COMPRESSED) Use a shorter spring. DONE PROPERLY, RIDE HEIGHT should ONLY be done by a separate adjustment that changes absolute overall shock length. YOUR SHOCK SHOULD NEVER BE USED AS THE TOPPING OUT OR BOTTOMING OUT DEVICE.....use rubber bump stops for that. Also note, that a shock without a separate reservoir is filled with lots of gas causing oil aeration and saturation. As the shock compresses, the volume of the shaft itself is now introduced into the fixed volume of oil....if there isn't any gas (air, nitrogen, whatever) to compress with the extra volume of the shaft, the shock wont move any farther...hydraulic lock. That's why (aside from additional cooling volume) reservoirs are preferred. In his last example the same size body shock with different sized shafts, the longer shaft will require more gas in the shock to compensate for the displacement of the shaft entering the shock....not better if you aren't using all of the shocks travel.
Let me guess - a motorcycle background? Bikes tend to explore the droop limit of their travel on a far more regular basis due to the extreme amounts of weight transfer they experience. On cars, we're more interested in getting as much overall travel as possible, with the emphasis on maximum compression travel. If you adjust sag (full droop), you have to give up compression. Or, in our case, we build for maximum compression because anything less is a dynamic compromise. And we always use bumpstops.
All shocks have some sort of gas in them to allow for changes in internal volume as the shaft moves in and out. On a monotube shock, that gas is separated by a piston so there's no chance of aeration. On some twin-tube shocks, it's physically separated in a bag or it's captured in the second tube - they rely on staying upright to function properly. Reservoirs are used to either give more fluid capacity or to separate bump and rebound damping functions on a monotube shock.
what a bad way to shell fox suspension,
We're simply providing engineering knowledge that will help you evaluate any suspension setup. Naturally our suspensions - all of them, not just the Fox - are designed using best practices. That's a benefit of being so closely involved with the design and testing process. If we were just picking parts out of someone else's catalog we wouldn't be able to do that as easily.
Did I miss something or did you start the video by saying "preload doesn't affect ride height @2:38" and then you end the video by saying you "set ride height by spinning the perch up and down @8:15."
Then @14:29 you say if you have a helper that is compressed at all times then you can "just take it out and move the spring perch up." Again not actually true in all circumstances. That is only true if you only care about ride height and don't care about maintaining droop travel. The helper adds droop travel. The fact that it is always compressed at static ride height is irrelevant. If you remove it you will gain travel in jounce and lose travel in rebound.
Preload does not affect ride height. The position of the perch when the car is on the wheels affects ride height. Preload can be all over the place at the same ride height as it's determined by what happens at full extension.
Take a spring/shock setup and then remove an inch of shaft extension - you can do this by putting a spacer inside the shock body. You have just increased the preload. But the ride height has not changed.
A lot of people are misled by inaccurate advertising or by vendors who really don't understand suspension geometry. Usually when people are trying to adjust ride height by "changing preload" they're changing another factor and the change in preload is just a side effect.
@@FlyinMiataVideo Yeah I can't get on board with how you are explaining preload. When myself and everyone else that is talking about coilovers mentions preload they are talking about SPRING preload. Spring preload being the amount that the spring is compressed when the strut is at full extension. Talking about the affects of strut preload is not comparable at all. Springs provide significantly more compression resistance than a strut. Not even at soft stock spring rates does the struts compression resistance have any meaningful impact on ride height. So you're right that preloading a strut isn't going to affect ride height (by any meaningful amount). I am not even sure why you think that reducing strut stroke by an inch means you've preloaded the strut either... that makes no sense. I think you simplified that too much. Anyway... you cannot say the same for springs just because it's true for struts. Preloading a 1,000lb spring 1" would give you 0 static compression on just about any road going car (actual change to ride height depends on motion ratio). Remove that 1" of preload and ride height goes down an inch or more. The only time that preload does not affect ride height is when you've preloaded the spring so much that putting the car down on the ground does not move the spring at all (preload exceeds corners weight). If you're goal is to dispel the myth that preload affects spring rate then OK I agree with that... but the rest seems a bit off base. I cannot see how you can continue to try to argue that spring preload doesn't affect ride height when in your own video you are telling people to adjust ride height by adjusting the lower spring perch. The lower spring perch produces preload, no preload, or sag in the spring. Seems like you are trying to redefine these common terms around your own suspension design/theory in what could be interpreted as misleading.
@@brendenbanks9293 Preload: the pressure on the perches when the shock/strut is at full extension. I think that matches your definition. "Strut preload" is not a term I've ever come across. I'm using preload as "spring preload".
Factors that affect preload:
- spring length
- spring rate
- distance from upper to lower perch at full extension (perch position and length of fully extended shaft).
Factors that affect ride height:
- spring length
- spring rate
- distance from lower perch to lower shock mounting point
(there are a few others such as upper mount design and of course corner weight, but we'll treat those as constants as they're not really relevant)
You can see that some of the factors that affect ride height also affect preload, but it's possible to change preload without changing ride height and vice versa. That's why we say that you don't adjust ride height with preload. They might both be affected by a change like moving the lower perch, but that's not cause. This is the important bit. Adjusting one does not necessarily mean you're adjusting the other.
In my thought experiment, I changed the distance from the upper to lower perch by changing the amount of shaft travel. The preload changed because thats one of the factors in preload. The ride height did not as that is not a factor in ride height. The car's dynamics will not have changed either until either the spring or shock is fully extended.
As mentioned in the video, there are edge cases where the preload exceeds the corner weight. In that case, you have a suspension that is fully extended at rest. This is not a functional suspension so it's not considered an important case - although we have seen it done. Your ride height is determined by the extended length of the shock in this case.
Most people who "adjust preload" and note a difference in behavior are really noticing other changes such as a change in bump travel thanks to a different shock geometry.
@@FlyinMiataVideo I took your comment about adding a spacer to the strut internally to reduce travel to mean that you were saying to increase compression damping force or something. Changing (reducing) the dampers stroke does not necessarily change preload if you can just move the lower spring perch down. Now all you did was reduce available rebound travel... If you assume that you leave the lower spring perch at the same height then you absolutely will be raising ride height. Why? because you increased the preload on the spring... Have you ever tuned a cars suspension with a divorced setup? Explain how the rear spring height adjuster works to raise ride height without saying that it "preloads" the spring. You can't. Sure there are other ways to raise ride height (longer spring/shorter damper body) but that all functions to increase preload and therefore ride height.
I am not going to go back and fourth because I think you are intentionally phrasing things in your list such as "- distance from lower perch to lower shock mounting point" affects ride height to avoid admitting that adjusting the lower spring perch up to compress the spring (preload) raises ride height. Again, this is up to that point where the preload exceeds the corner weight. The fact that the ride height ceases to rise once the corner weight is exceeded DOES NOT mean that preload isn't what changed the ride height... Also, reading the statement as it's written, without making a bunch of assumptions, can easily be interpreted as being false. The distance between the lower spring perch and the lower strut mount in and of itself has no bearing on ride height. You would need to make a specific statement such as "adjusting the lower strut mount up/down changes ride height" for it to be correct. which it is true... even if you want to argue that the lower damper mount should NOT be used as the primary method of changing ride height. To prove the statement is false I can just say something like " I put in a longer spring. Since the spring is longer I moved the lower spring perch down. The distance between the lower spring perch and the lower strut mount has now decreased; however, ride height has NOT changed." All you've done is changed to a spring with different stroke. Given that you keep preload the same the ride height will not change at all!
I don't necessarily think you'r "wrong." you clearly understand how it all works... I just think you're trying to differentiate yourself from other suspension brands by making the same type of misleading statements... they say "X" is how you do it so you're saying "no they're wrong it's Y." Reality is that both are true given the right context.
@@brendenbanks9293 Here's the problem:
"If you assume that you leave the lower spring perch at the same height then you absolutely will be raising ride height. Why? because you increased the preload on the spring... "
That's just plain wrong. Once the car is sitting on its springs, it has no "memory" of what the preload is at full extension. Preload does not affect ride height.
Things that affect ride height - such as perch location - can affect preload. But preload itself does not affect ride height unless it's higher than the actual cornerweight. Check with your high school physics teacher. Once there is X load on the spring, it will compress a certain amount that is dictated solely by spring rate. This is the fundamental misunderstanding here.
Numerical example: take a 300 lb/in spring and a car with 600 lbs of corner weight. When the car is on its suspension, the spring will compress 2". Right? Now, set the shock up so there's 75 lbs of preload on it (spring is compressed 1/4" when the shock is at full extension) but without changing the perch position relative to the lower mounting point - say, you can do that by limiting droop as I specified earlier. Put the car on its wheels and the spring will compress 2" because there's 600 lbs of weight on it. It still has the same spring rate. The wheel won't start to move until there's 75 lbs of load on it, but the end result is the same. Voila, no change in ride height because the length of the compressed spring is the same, as is the distance from the bottom of the spring to the lower shock mounting point.
My list of factors stands. In your example where you increase spring length (ride height goes up), you have to change another factor (shorten the distance between the perch and the lower mounting point) to keep the same ride height. So you're adjusting two factors in opposite directions to maintain the same ride height. Both of those factors are ones that are shared with preload so coincidentally you're also keeping the same preload. But that's not the only way to affect ride height, and other methods don't necessarily affect preload.
I've been messing with Miata suspension for a couple of decades. I've run setups with multi-piece bodies, which I think is what you're referring to as a "divorced" setup. With that setup, you can change the preload without affecting ride height by shortening the body. Or you can change ride height without affecting preload. Which proves that it is not preload that is changing ride height. There are simply several factors that can affect both, and some people think that means the two are somehow interrelated.
But what's also important is that the preload doesn't matter other than our edge cases! Even if you believe that the ride height is set by preload, it's irrelevant. The only time it affects suspension behavior is when you're at full extension, which is pretty rare. So preload is not a tuning tool on a car. On a motorcycle that sees much more radical weight shifts than a car, it can come into play when you've got a fully unloaded wheel.
(apologies to all the engineers and physics teachers for playing fast and loose with force and load and weight)
When the preload is not separated from the height then you are directly shortening the entire suspension travel by adjusting the perch level which you would need to do to if you want to lower the center of gravity of the car.
When preload is separated you maintain the same suspension travel while lowering it. How would this not be considered a "tuning" feature?
If someone is just looking to replace stock shocks without changing the center of gravity then ya you are better off with a single body unit but that's only half the story and in no way grounds to call it a "Myth". Both styles cater to different purposes and you are acting like your style is the only style. Even Ohlins has designs with with separated height and preload adjustments and i definitely wouldn't call them hack-jobs...
What you're missing is that there are other limits to suspension travel. A good Miata one-piece shock will be designed to allow the maximum compression travel the suspension can physically provide before something else stops it - control arms vs subframe, ball joint range of motion, tires into shock towers, etc. Using an adjustable length shock will not give you any more than that - but it will give you the ability to limit your compression travel (bad) and will limit your overall travel due to the shorter shaft travel inherent in the design (bad). This is the thing that everyone overlooks. No matter what the ride height, the one-piece design will give you maximum compression travel and more droop travel than a two-piece.
The two-piece design is the weakest aspect of the Ohlins, and I will happily call them a triumph of marketing over engineering in this case. You can feel them topping out over crests due to the short travel.