Rear suspension spring rate for coil overs

[ViperGT]

I'm going to purchase rear ground control coil overs and wondering what spring rate I should get

 

[datzenmike]

I'm going to purchase rear ground control coil overs and wondering what spring rate I should get

 

 

That's like asking someone to pick out your future wife for you when it really would depend on your preference in ride quality. 510s can range up to 1000lb rate on the backs because of the suspension design. If possible find several 510s with a known spring rates and go for a drive in them and compare. Better to be softer than you want that too stiff. Keep in mind that tire compliance and shock absorbers are also a factor in the ride 'stiffness'.

[datsunfreak]

Also, what kind of car is it? :P

 

Assuming Mike knows it's a 510 and I somehow missed that, It helps to tell us what you're planning to do with the car.

 

A lot of people start at a wheel rate of 200 or 225 and either go up or down from there. They're relatively easy to change, and cheap to buy, so you can always get 2-3 pairs and see what you like?

[datzenmike]

I suppose it could be a 610 too, just assumed 510. Datsunfreak, aren't the rears much higher than that??? Front stock springs are about 100psi but usually they are upped by twice that.

[datsunfreak]

I suppose it could be a 610 too, just assumed 510. Datsunfreak, aren't the rears much higher than that??? Front stock springs are about 100psi but usually they are upped by twice that.

 

Rear springs in the stock location are much higher, usually 500-800. Once you go coil-overs you get the springs closer to the wheel so the spring rate is closer to the wheel rate.

 

Basic rule of thumb, with coilovers the wheel rate and spring rate are within 5-10% of each other.

 

Springs in the stock spot means multiplying wheel rate times 3.8 to get the needed spring rate. So to get a 200 pound wheel rate you need springs in the 750 range.

[FiveTenzo]

He said he's getting rear ground control coilovers, so why would he be interested in spring rates as high as 800 or 1000?

 

Anyways, I'm running ground control coilovers 300lbs front and rear on my 510 daily driver.

[datzenmike]

Because stock springs are mostly a compromise with comfort before handling performance. Pretty safe to say that increasing the spring rate improves the handling.

 

Springs in the stock spot means multiplying wheel rate times 3.8 to get the needed spring rate. So to get a 200 pound wheel rate you need springs in the 750 range.

 

This is because the 510 rear is based on a cantilever design. There is a hinge point, the spring and then the wheel. The spring is not directly over the wheel but closer to the hinge or fulcrum point. This acts like a lever and there is a mechanical advantage for the wheel so the spring must be of a higher rate. 1000 PSI is closer to a race set up but 750 isn't that crazy stiff for a 510 I believe.

[datsunfreak]

He said he's getting rear ground control coilovers, so why would he be interested in spring rates as high as 800 or 1000?

 

 

Actually, he still hasn't even said what car this is for. 1000 pounds might be good for a Humvee? :P

[ViperGT]

haha oh i forgot to mention i will be going to track days at willow springs 1-2 times per month and it is a 510 with a ka in it, the front has ground control/koni inserts but im not sure of the spring rate cause i bought it like it is and i think the shocks in the front need to be rebuilt, and its a daily but i like a stiff ride comfort isnt a need.

[Uber Deaf One]

I recently was running 225/236 lbs... switched to 275/294 and actually gained front grip. My 510 was actually undersprung with the 225s

 

I'd start at 275 all around if you're serious about those track days.

[ViperGT]

ok will do thamks!