rkb58

Hi all, need your help and opinions. I would like to do this right the first time, if possible.

I am a track addict, 63 days in the last 1.5 years. Most of these days have been in a very stiff BMW E30 325is race prep'd car. I run hard on the track, and have enjoyed progressing to instructior level with PCA and other clubs.

I enjoy running with varions PCA groups, so I got an '86 951 a while back to develop into a DE car in order to save my BMW for NASA and BMWCCA racing.

The 951 motor is and will remain stock unitl I get the suspension where it will work. Before taking the 951 to the track, I put in second hand but relatively new Paragon Koni coil over conversions up front with 200lb springs, and new KYB shocks controling stock Torsion bars on the rear. The car has Turbo S sway bars, 26.8mm F, 18mm R. The car currently weighs about 2890 lb.

Tires are either a combination of 225/50/16 Front/ 245/45 rear Toyo RA1's on Turbo S club sport wheels or 225/45/15 RA1's on all corners on old OZ 3 pc wheels. Yes, the 15" OZ wheels clear the turbo brakes.

With the 225/245 stagger combo, the car pushes horribly, to the point that it is almost work and not fun to drive. There is a lot of body roll.

With the 225's all around, there is a lot of body roll and "floating", but the car is fun to drive. It rotates well at the initial turn in point with a bit of trail braking. Biggest problem with the 15" setup is that the tires give up after about 15 min. There is just too much weight, I think.

I have scrounged up a set of 4 ea 9" club sports and another set of 4 ea 8" phone dials in order to run 245/45/16 RA1's on all 4 corners.

So, at last to my question. What do you track experienced rennlisters think is the stiffest setup that is still somewhat streetable, that will not result in horrible understeer or excessive oversteer with 245's on all 4 corners? I know that stiffer would be better for the track, but I already have a miserably stiff for the street race car. I don't want to create another race car (yet). I want to be able to somewhat enjoy driving the 951 to the track. I'm thinking something like 350lb front springs and 29mm rear T bar?

Please let me know what you'all think. I did search rennlist prior to writing this, but did not read a thread that addressed the TRACK/street compromise specifically. Yes, I know that it might wind up not optimum for either application, but I want to try.

Thanks, Robert

billthe3

I don't have any experience with this officially, but I recently posted a thread about the paragon koil over kit for the front and learned that if you don't do anything with the torsion bars in the rear the car will understeer like a bitch. Skip from paragon recomended running 27 or 28mm torsion bars in the rear with 250lb springs up front - 27 to be pretty neutral and 28 to be a little more rear out. Here is the original thread so you can read yourself (some other good info in there). https://rennlist.com/forums/944-turbo-and-turbo-s-forum/295237-paragon-front-coil-over-kit-opinions.html

Thats only for the issue of the car pushing though, not any info about whats to stiff for the street. Was sort of wondering myself the other day how stiff the 250lb springs in front would be...

rkb58

Skip, Thanks for the reply. For me, 200 lb front is still very nice for the street. I think my 951 is, somehow, more comfortable on the interstate, than my Mercedes 300E.

xsboost90

im getting ready to go 400lb front and 375 rear coilovers on my 86 951. Ive driven a few w/ the same settup and if you dont have hard racing seats i dont think it would be that bad really! For best comfort and track drivablility i would go 300 up front and some light coilovers in the rear-not sure what LB you would need though- im going to try these 375 rears and see if thats too much- may have to downgrade alittle. I'll post how it rides when its done in a few weeks.

sidsport

I've just done 375# front w/ adj kit and 30mm torsion bars on my S2. Haven't had much time on the street yet, but initial reaction was more wahoo than crap my teeth are rattling. Haven't been to the track yet either (VIR in 3 weeks!!!), so I can't comment on the changes there. Coming from stock springs and t-bar and M030 sways (30 and 19) with Titanic body roll. Also added adj camber plates which won't help on the luxury end. You're right on with the new wheels/tires to run 245/45/16 on all corners. Keeps it simple and lets you rotate. I should also mention that I have koni single adj inserts up front and Bilstein non adj in rear (Jason at Paragon thought the shocks could handle those springs but probably not much more). My last $.02 (I've spent a bit of change alreay) is don't fear the torsion bar. Dunno if you aim to do the work yourself, but the indexing of t-bars really isn't that bad if you follow Joe P.'s spreadsheet (sorry don't have the link handy). Last thing, might want to change bushings while you're in there. Good luck....

Trucho-951

Robert, I have 250# springs, 28 mm T-bars, and 19mm rear sway bar adjusted to the third tightest hole and Koni yellows. I think the car still rides very comfortably on the street, my wife even likes going for rides around town ever so often. At the track the car handles mostly neutral with just a slight hint of oversteer. I think it's a great street/track compromise.

You'll also want to look into replacing your lower control arms with aftermarket (Racer's Edge, Charlie Arms, Blaszak, etc.), since the balljoints are the Achilles heel of the 951. Do a search and you're guaranteed to find a wealth of info on the topic....

Litespeeds

I have Koni adjustables set on stiff on all 4 corners and put 350lbs front springs and 30mm hollow rear torsions and the ride is surprisingly good. The swaybars are 26.8 and 18mm rears. I have a 1988 944.