Thread: Spring rate trade offs

Heres the suspension setup so far:

Bilstein HD's.
Vogltand springs spring rates: 200/140
Dorman front sway bar, 33 mm solid.
ADDCO rear sway bar, 22 mm solid.
GMPP trailing arms.

Things that dont matter:

ZZP STB's, poly sway bar bushings and front end links. Moog rear links.


Its not comfort I'm concerned with at all.

I wouldn't care if it the car beats me up all the time.

Yes, have been in cars that do that for extended periods of time and driven them.

Car is already a little harsh on the bumps.

ZZP ships their coilovers with 350/275 spring rates.

I think this will be a little high for maintaining traction on the rough roads that we have around here.

I'm thinking a nicer compromise would be 275/200.

Similar increase as going from stock (143/120) to the vogtlands.

Just need to talk to more people running spring rates that high.

my coilovers have 7 kg/mm front, 5 kg/mm rear. that equates to about 390 lbs/in front, 280 lbs/in rear. it was a rough ride, but then again my struts were probably valved by retarded people. handled pretty well, though.

doing it again for a better handling car that i could keep off the ground more readily i would jump up to 8k/6k (~450lb/335lb) like most of the aftermarket coilover manufacturers use for my car.

knowing that the grand prix is a heavier car with a lot more load to shift around, would you consider going higher than your initial numbers?

yes, mcpherson strut.

traction on rougher roads did kinda suck, but ill admit i never pushed it really hard. i did take a few left hand turns through lights at a couple rough intersections and the car seemed extremely unstable because of its ability to take flight due to the spring rates. however, on flat roads (on/off ramps for the highway) it worked pretty nicely. my new spring/strut setup would be no match for it prior to the swap on a little road racing course.

knowing that the car has a natural tendency to understeer A LOT, i would probably opt to bumping the rear spring rates more than you'd be bumping up the front. that, applied with a bigger rear sway bar may be able to cure a lot of the handling issues this car is famous for.

however, since youre trying to keep the rates light to trade off handling for ride comfort im not sure this arguement is worth having.

my car is a little more balanced and the RWD bias of the AWD system does lend itself to being able to run higher rear spring rates, i agree with you there.

however, i think the same concepts would help out, even on a FWD car. right now you have a car that cant get the ass end of the car around to save its own life. bigger, stiffer everything in the back would help this situation out.

honestly the best thing to help out this car would be a subframe brace, but no one is going to take the time to make one.

what do you think would make a better addition?

do it then, skippy.

Not sure how much it honestly helped because I did it all at once.

The rear STB seems to help a little for chassis flex. Maybe that's a first low cost step to see if something in the trunk could help the issue.

The other things I did were to oversize and poly the toe link and lateral arm. Those typically flex a lot from the factory.

Originally Posted by BillBoost37

Maybe that's a first low cost step to see if something in the trunk could help the issue.

That makes me things. A lot of the older RWD cars have cross braces behind the backseat to provide structural support and prevent body flex and roll. That could be a possibility.

when i put my next one together i planned on deleting the rear seats and putting in a half cage to stiffen up the mid section of the car. most likely i would bind this cage to the rear end of the car in some fashion.