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Learning how to tune suspension. Kindergarten level.

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Learning how to tune suspension. Kindergarten level.

 
Old 07-21-2017, 10:17 PM
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Default Learning how to tune suspension. Kindergarten level.

Hey guys, so I just did my first autocross last weekend with the semi-almost-kinda-finished car. I have a ton to learn about how the car drives and feels as well as navigating and learning courses better. I would like to learn more about each part of the car that I have assembled, and this thread is about my suspension.

Current setup: Tokico Illumina, FM springs, Jackson Racing solid adjustable front and rear sway bars with FM endlinks, R1R 225/45/15 on 15x9 6UL. Nothing in the way of chassis stiffening other than a roll bar.

I realize my first mistake last weekend was I probably should have unhooked my rear sway bar - the car was a bit tail happy on the course which was basically two long slaloms and one fast curve. I also should have taken my hard top off to lower the gravity of the car a bit. I had my shocks on setting '5' on all four corners and both sway bars were in the middle/moderate setting. I had just also gotten an alignment with FM specs.

My question is, what are the things I should look at in my suspension settings with my setup? I really don't yet understand how everything I have assembled ties together. Just want a better understanding on what having a proper suspension setup really means. Party on.
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Old 07-22-2017, 10:00 AM
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The best tip I can give you for dialing in a set up is to have good fresh tires. You can't set a car up on old hard tires, unless of course, you are never planning to run on new fresh sticky tires.

The rest is trial and error. Sway bar settings, shock settings, tire pressure, alignment including rake and toe, etc. All of these things can affect how the car feels and you don't always need to make broad changes in order to get the car to what you want it to do.

And also, everything needs to be in good working order. If bushings and sway bars are binding or you are always on the bump stops, a multitude of changes may have no affect on an issue you may be having.
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Old 07-22-2017, 10:15 AM
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Tires are pretty good, maybe 1200 street miles with one autocross on them. With my motor swap i also replaced every bushing in one go, that $5 tool did a hell of a job!

Over the next few Autocrosses I'll try different settings and see what works and what doesn't. I probably could have lowered my tire pressure a bit too seeing as my wear line didn't touch the mark. So lots of trial and error it is! And maybe another set of tires after these bite it lol. Thanks for the input
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Old 07-22-2017, 10:23 AM
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Well, if you're happy with your setup, that's great. However it's an incredibly basic setup with very little adjustment. I guess I'd start by checking for sway bar bind and preload. Disconnect both end links and make sure the bar swivels easily. If it doesn't, try greasing the bushing. If that doesn't work, you'll have to shave the bushing which is a REALLY common thing on RB bars, not sure about JR. And unless you have an NB (don't know?), I don't like the FM end links due to the bushings. If they're not banned by class, I'd grab some 949 end links and throw one on. Adjust so when the car is on a level surface the sway bar is level. Then install the other one and adjust for no preload. You'll feel as you move the adjuster there's one setting where you're not jacking the bar up, or trying to pull it down. Do the same for both bars, put the front at full stiff and the rear at full soft and see if you're still tail happy.

Other than that, you're really out of options. You can't lower the car AFAIK, or corner weight it. I guess go a little softer on the rears, or stiffer on the fronts, usually you don't set Miata shocks to even all the way around. And with 225 R1Rs and 15x9s, once you get good you're going to blow your suspension to pieces. Especially on a track (if you ever plan on that), you'll find you have a pretty big lack of spring and dampening.
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Old 07-22-2017, 10:24 AM
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I'm not familiar with that tire but I would assume it's similar to other super 200's just without the ultimate grip. So a rather stiff sidewall and a good sized wheel with a light car in the miata likely means mid 20's for pressure. Tire roll over is not a good indicator for pressures. A pyrometer and a stopwatch are.

Also, tire pressure is a decent tuning aid once you have established a baseline pressure. On less sticky surfaces I like to run a pound or two less pressure all around. Or if the car is loose, drop rear pressure and vice versa if tight.
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Old 07-22-2017, 01:42 PM
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Originally Posted by curly View Post
Well, if you're happy with your setup, that's great. However it's an incredibly basic setup with very little adjustment. I guess I'd start by checking for sway bar bind and preload. Disconnect both end links and make sure the bar swivels easily. If it doesn't, try greasing the bushing. If that doesn't work, you'll have to shave the bushing which is a REALLY common thing on RB bars, not sure about JR. And unless you have an NB (don't know?), I don't like the FM end links due to the bushings. If they're not banned by class, I'd grab some 949 end links and throw one on. Adjust so when the car is on a level surface the sway bar is level. Then install the other one and adjust for no preload. You'll feel as you move the adjuster there's one setting where you're not jacking the bar up, or trying to pull it down. Do the same for both bars, put the front at full stiff and the rear at full soft and see if you're still tail happy.

Other than that, you're really out of options. You can't lower the car AFAIK, or corner weight it. I guess go a little softer on the rears, or stiffer on the fronts, usually you don't set Miata shocks to even all the way around. And with 225 R1Rs and 15x9s, once you get good you're going to blow your suspension to pieces. Especially on a track (if you ever plan on that), you'll find you have a pretty big lack of spring and dampening.
Thanks Curly! I understand it's basic, I went off of recommendations for a decent street setup, but I guess probably not an amazing performance setup. You've made me realize that I think I forgot to grease my bar bushings. What about the bushings on the FM links do you not like? Lastly, in what way will the suspension get blown to pieces? Should I just plan for Xidas soon? lol
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Old 07-22-2017, 03:56 PM
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Last edited by Art; 06-11-2018 at 07:11 PM.
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Old 07-22-2017, 08:52 PM
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Originally Posted by Art View Post
The compound is what determines grip with section width being mainly for dissipating heat. A thinner tire will provide the same grip but will overheat and get greasy faster than a wider tire will.
Not necessarily true. Better heat dissipation is tire compound dependent. Section width helps with this, but tire compound is the main factor here.

A wider tire will be faster than a skinnier one. A 245 r7 (for example) on one hot lap will be faster than a 205. Plain and simple. More mechanical grip.
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Old 07-22-2017, 10:18 PM
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I think Curly is referring to the fact that your tire/wheel combo can generate a lot of grip and your coilover setup will be struggling to support the cornering loads once you progress in skill.

First thing I suggest is a notebook or some form of data tracking to keep tabs on your setup, lap times, and notes after each session. I support getting adjustable endlinks. This is because you can zero out static swaybar loads which I have seen throw off cornerweights. To do this you need to park on a level surface, install the links, and adjust the lengths until the heim joints can "easily" rotate. It should be pretty clear when the swaybar is no longer statically loaded.

Only make one change at a time and record how it affected the handling. Look into your rear toe settings to see how toe in/out my help with settling the rear and preventing oversteer.

"How to make your car handle" by Fred Puhn is a dated but good resource.
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Old 07-22-2017, 11:57 PM
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Thanks guys! I appreciate the feedback. As a noob this is going to take time to learn but I'm gonna keep at it. After this thread I realized i have a couple more thousand dollars to spend to really tease out what the car is capable of, but that's probably over the next year. I'm in SSM because i think my built motor swap. It'll be turboed soon as well, so that'll be fun. I'm gonna check out those books.

Looks like the future holds: 275s and 11" wheels, Xidas or comparable, BBK, is lexan easy to work into a big spoiler? I'm having a ton of fun so far and have to learn how to drive this car. I wish more events were closer so i can try more. Getting 4 or 5 runs every few weeks isn't enough 😩 I ain't about that street recklessness
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Old 07-23-2017, 10:59 AM
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I would move my F sway bar to the full stiff setting (inner hole), and R to full soft (outer hole) -- that's how I had my JR sway bars setup.

then it comes down to tuning the damping on the shocks and tire pressures. Keep the rears adjusted a bit softer than the fronts if it's over-steering still too much, and same with tire pressures. increase the pressure on the front tires so they would lose traction first.
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Old 07-23-2017, 11:18 AM
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A slightly oversimplified explanation of shock tuning is to think of your shocks as a tuning aid for transitional situations. When you first turn in the shocks will influence the balance while sways and springs will dictate mid corner and exit balance.

This isn't always the case, and their are a ton of other variables but I betcha once you get the car balanced like you want with the sways you can get the car to either push or be loose on turn in with your limited shock adjustability.
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Old 07-23-2017, 11:19 AM
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Originally Posted by Bronson M View Post
A slightly oversimplified explanation of shock tuning is to think of your shocks as a tuning aid for transitional situations. When you first turn in the shocks will influence the balance while sways and springs will dictate mid corner and exit balance.

This isn't always the case, and their are a ton of other variables but I betcha once you get the car balanced like you want with the sways you can get the car to either push or be loose on turn in with your limited shock adjustability.

pretty much exactly what I was suggesting.
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Old 07-23-2017, 12:05 PM
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Yeah sorry wasn't trying to repeat, guess I was trying to point out the concept of breaking up a turn into sections and where each piece of suspension plays a role.
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Old 07-23-2017, 12:58 PM
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i was suggesting we are either both smart or dumb, together.
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Old 07-23-2017, 01:38 PM
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Thanks guys, the explanations given so far are really helping me understan how the suspension ties together. My rear was entirely too stiff last time so that's going to be first change. What are the pros and cons of disconnecting the sway bar versus having it on the softest setting [edit: why would i buy a new bar if I'm just gonna have it disconnected]. I didn't notice understeer as much as the *** end trying to outrun the front.

Last edited by Philly Miata; 07-23-2017 at 01:51 PM. Reason: Am dumb
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Old 07-23-2017, 01:40 PM
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Originally Posted by Philly Miata View Post
Thanks guys, the explanations given so far are really helping me understan how the suspension ties together. My rear was entirely too stiff last time so that's going to be first change. What are the pros and cons of disconnecting the sway bar versus having it on the softest setting? I didn't notice understeer as much as the *** end trying to outrun the front.
What's what's the point of buying a sway bar if all you're going to do is disconnect it the whole point was improved performance. You might however be better off going back to the stock rear bar...
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Old 07-23-2017, 01:50 PM
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Originally Posted by Braineack View Post
What's what's the point of buying a sway bar if all you're going to do is disconnect it the whole point was improved performance. You might however be better off going back to the stock rear bar...
I realized that was dumb as soon as I posted it. I'll try the soft setting on the JR bar and compare to the OEM bar. What was your experience with comparing the two, Scott?
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Old 07-23-2017, 02:11 PM
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I went stock rear with tiens, and front JR on stiff.
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Old 07-23-2017, 02:44 PM
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Originally Posted by Braineack View Post
I went stock rear with tiens, and front JR on stiff.

That reminds me to ask while we're on it even though I can search. Teins seem to be pretty popular. Is there a tier list of performance shocks and coilovers? After this thread I realize I am limited by my Illuminas because they are pretty basic and not height adjustable (how much difference does this make anyway?).
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