I've got a set of Ground Control Weight Jack adjusters & 2 sets of springs...150lbs & 225lbs

The question is...Which ones to run? I don't drag race. I'm not even interested in drag racing. The car is a driver/autocross car.

Are 225lbs TOO stiff? Or a good compromise between driver & autocross? I'm still running stock WS6 front springs, but intend to get some Ground Control Weight Jacks for the front as well, & possibly go for fronts in the 850/900lb range.

Suggestions?

 

Are you talking about the front Coil over set up that goes over the front struts? If so 850-900 will be to stiff. On the strut it is a 1:1 spring rate/wheel rate ratio while the A-arm mounted spring will cut the spring rate nearly in half. I would be thinking that you would be looking at no more then 500 lb springs in the front with a coil over setup.

Just as a point of reference. In my dedicated CP autocrosser I have 1200lb(Aprox 600 lb wheel rate) front and 425's in the rear, small sway bars front and rear and have understeer. It will take lighter front springs and heavier rears to get the car to do what I want. I am probably looking at close to a 500 lb wheel rate front and rear when I am done and maybe removing the rear bar.

 

Well, my thread title was REAR coils, not fronts. I only mention the fronts, because I KNOW somebody will start talking about fronts anyways.

I'm looking for an opinion on REAR spring choice, not the fronts.

 

im using the rear coil-overs that Spohn sells, with a 175 lb spring, seems to work well. I think 225 is just a tad much

 

Sigh....

I'm NOT talking about coil overs.... Ground Control

About half way down on the page, you'll read this....
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Adjustable rear ride height kits
Aluminum threaded adjuster, installed below spring, no welding required $92.00 pair


Replacement rear springs
Racing rear springs All of our rear springs are made exclusively for us, but the most popular by far is made by Suspension Spring Specialists as a 225 lbs./in. rear spring. These springs are designed shorter than circle track springs, and do not need to be cut $55.00 each
Racing rear springs, 125 lbs./in., 150, 175, 200, 250, 275 ,300 $59.00 each

 

Yeah! Don't let it happen again!!!! lol

 

I would think the 225 are too stiff for street use unless you've lowered your rear roll center (lowered PHB). I've decided on 750 or 800 lbs front with 150 or 175 rears for mine when I do the jacks from research on FRRAX. I'd stick with the 150s. I'll see if I can find the thread for you.

Here it is. Might be helpful.

 

I have 800ft/150rr (factory style springs) on my 91 WS6. They seem to work well, but I did have to reduce the rear bar size to a Strano 22 hollow as it was slightly loose on the street. Now I love it. Front is a little harsh on bad roads, but I still drive it 60mi a day. If I had a set of rear 175's I'd try them for curiousity, but would not buy a set as I have my doubts. Overall I'm very happy with the results.

 

Stephen,

Not easy to suggest a rear spring without knowing what front spring you are going with. They do compliment each other. That is why I used my car as an example. I think with my car, Wheel rates that are very close to matching would be about perfect but my rear suspension is a bit different then yours(3 link compared to torque arm)

As far as wseight jackers I went here http://www.ground-control-store.com/...hp/II=20/CA=67 and this is what I saw so I was asking for a clarification because it would make a huge difference.

Here is my suggestion, After you decide what front spring you are going to use, Try both sets of rears and see what you like the best, it only takes 10 minutes to change the rear spring, so easy that you could do it between runs at your next autocross. Every car is different, every driver is different. Find out what you and your car like the best.

 

stephen,

AFAIK, a 2.5" coil over spring with a spring rate of 250 lbs, and a 5" standard coil spring with a spring rate of 250 lbs will act exactly the same, so i was trying to give you a point of reference.

 

Hmmm, I also thought that coilovers were measured at a different spring rate than regular coils. Later.

 

ASAIK, spring rate is spring rate. However, since the front soil over setups that get used on a 3rd gen are located on the strut, a lighter rate is used with the same result as a heavier rate in the spring pocket, a matter of leverage.

 

so wats the part # for a 175lb rear spring rate for a 3rdgen firebird? from the ground control website? i have sportlines but the rears are too soft, i just bought moog 5665 replacements but i dont think theyd be stiff enough even if i hacked off a full coil off the rear to get the same ride height as the sportlines. i have the added weight of 80lbs over the rear seats due to a 6pt roll cage. and im running true dual 3" so i need more spring rate bc i kno my sportlines will bottom out prob