I am purchasing the coil over conversion kit for my Koni "yellows and need some help on the spring rate.

I have the rear shocks at maximum stiffness and the front shocks have the Weltmiester springs that are supposed to be a little stiffer than the coil overs that came on the 88 and 89 turbos but I dont know the rate so what do you guys recommend for me?

This will be a street car with some track use so I dont want something that is to harsh yet I want performance to at least match the factory MO30 set up that came on the 88 and 89 cars so can anyone give me some ideas on the spring rate for the front springs for the coilover kit.

Thanks in advance.

 

I take it that you have the stock torsion bars in the rear? If that's the case then you probably don't want to exceed #200 or so. There's lots of folks here that know volumes more than me about suspension so take this for what it's worth but dialing up the rebound damping all the way up to "stiffen" up the car is likely to be counterproductive to speed at the track.

 

If you have stock torsion bars in the rear and your rear shocks are fairly fresh, I think you will like the handling better if you reduce the rear shock stiffness to around 2/3. Tends to skip sideways on choppy pavement on full stiff...

 

Russ and Grant,
I do have the stock torsion bar and my KONI'S are in excellent shape.

I just did a search and found that there have been problems with the 8 inch spring in that a spacer must be used and that going with the 10 inch spring works better because no spacer would be needed as you wouldnt be at the limit of the collar.

Correct me if I am wrong but I am running KINESIS 17 inch wheels so would it be a must for me to go with the 10 inch spring? Now I have 2 questions to answer.

 

It depends upon the spring rate you choose(rate=pounds required to compress 1"). If the tires you select for those 17" wheels result in an overall diameter greater than stock then, yes, you probably need 10" springs with a rate approximate to #200. I used 8" #200 springs when I went to the coilovers and needed spacers to keep my ride height with 16" 225/50 wheel/tires from being to low.
Having spacers on hand is not a bad thing.

 

So Russ, do you think a #200 or #250 spring in the front would work well with a stock turbo S 25.5 torsion bar and 968 M030 sways? I'd like the front of my car a bit stiffer, but don't want the hassle of replacing the torsion bar or reindexing it for rear coilovers. I'll be installing double adjustable Koni yellows in the front as well, but as you say, cranking up the damping is no substitute for stiffer springs.
Gary
'89 951

 

Gary,
I'd say #250 would be ok with your #175 effective rear rate. My #200 fronts with my 23.5 torsion bars would be analogous to you running #277 on the fronts with your 25.5 torsion bars. This is a handy little spreadsheet: <a href="http://members.rennlist.org/dan10101/944SpringRates.htm" target="_blank">944 spring rates</a>

 

Thanks for the spreadsheet, Russ. Lot of variety in how those cars are set up. I'm thinking 250# front springs will work fine with the rear swaybar set full stiff, maybe with harder bushings as well.

 

The spreadsheet is great Russ, thanks. BTW the link doesn't work it has an extra http:// in the beginning. Just remove that and you can get to it.