how to get spring rates for your car

Hey guys. Its wesman. I got really bored and started doing research on suspension and stuff. And I found something interesting.

First of all how to determine the rates needed for your cars situation.  Well since they will all be racing oriented, we need to know how much load is transfered from side to side going around corners. Typical rule of thumb for street cars with an average wheel base (left to right) is 70%-75% That's 75% on the side of the car under load. That leaves 25% on the unloaded side obviously.

Now to work out the proper spring rates for the car.
I'm going to use a silvia S14 for example.
I bought one and upgraded springs, diff, and the driveshaft only just so it would stay at 2800Lbs.
So now you need to figure the rates for a spring under load.
We do this by(using a calculator cause I'm lazy and stupid) ×2800 by .75 which is 75%

So it would look like this on your calculator  →→ 2800×0.75 = 2100
Now you take 2100 and divide it by 2 because there are 2 springs under load while cornering.
So 2100÷2 = 1050. Now I know it looks way too high but that's where the other 25% of the car comes in.
That weight is what compensates for the loaded side letting the springs absorb some weight transfered. Its weird I know. Anyway. So we take 1050 and × it by .25 (25%).
So 1050×0.25 = 262.5. Now we take 262.5 and subtract it from 1050 so 1050-262.5 = 787.5
And there is your spring rate.


(↓↓↓IMPORTANT↓↓↓)
Now you have to take weight distribution into account as well. After upgrading to race springs the stock tune will show its spring rates. Those rates will show the weight distribution. All you have to do is subtract the lower number from the higher one. Then once you've got the new rates add or subtract the difference depending on drivetrain to keep the weight distribution.

If you guys have anymore questions regaurding anything in suspension tuning just post below. I know how everything works and I'm willing to help.

Hi wesman.

Hey koolaid

Nice research Wes I think I've seen that before on FM.net.

But I use unadjustable sport springs anyways so LOL  

Well as far as suspension rates go I just look at what a street car would have in real life for a suspension setup and go from there. For example the AE86 should have suspension no stiffer than 6kg front and 4.8kg rear for street use. So you could use that as a base setup and soften or stiffen it until you get what you like. I don't really know about other cars though so google would probably be your best bet for that.

Hi Kraze,
Hi Beta.

Yea I used to look up the the most common rates for streets cars. But then I realized we don't street these cars. They are dedicated track cars. So softer rates for a daily driven vehicle are kind of useless on here. I started using this method and my times have all improved by at least 1.5-2 seconds. I guess because I spend a lot less time trying to get the right spring rates. And now I just spend time tuning dampers. It works for me. Just figured I would share.

Hi koolaid

this seems interesting im gonna try that method on some cars

Hey if you guys do try this, please give me feed back on your results. I'm still trying to work on fine tuning the math to get a formula that will yeld the best results.

can do that ill post my experiences in here

I tried this with an MR2 I have been messing around with and I saw improvements as soon as I hit the first turn. I was having understeer problems with this car but now it grips really nice. I'll make sure to remember this for future reference lol.

I got the first part on your calculations to get the Spring Rate, can you go through the example a little more with examples? Little confused by "(↓↓↓IMPORTANT↓↓↓)
Now you have to take weight distribution into account as well. After upgrading to race springs the stock tune will show its spring rates. Those rates will show the weight distribution. All you have to do is subtract the lower number from the higher one. Then once you've got the new rates add or subtract the difference depending on drivetrain to keep the weight distribution.

Math... not my strongest subject. i just like to go fast around the corners!! lmao XD

Moving this to a more suitable section.

Does damping and rebound impact the suspension distribution settings?

yeah

I gave this a try for my sw20 and it made a significant difference! thanks

I'm trying this on my 037.

So I have my suspension down. Is there anything to determine rebound and damper rates?

I was never able to figure those out that's why I quit tuning race suspensions.

I know i found it on a forza drift forum but a good starting place for me was to do it like this:

(max setting - min setting)

then multiply by front weight distro (e.g. .51)

then add min setting

repeat for rear rebound but with rear distribution (so in this case .49)

then the bump is ~half of your rebound stiffness

after that tweak to feel

EDIT: I believe max and min are 12 and 1 respectively on all suspensions

Nice i drive a s14 now i don't have to do the math

Thanks, Peacock.