ckkrause

Thanks for looking! I've got an '88 924S that is used for DE/TT and occasional daily driving. It currently has Bilstein HD shocks, 200# Welt springs in front, stock 23.5mm torsion bars in rear, 26.8mm front sway and 18mm rear. I also have lowered the rear as far the eccentric will go, but the car is still slightly nose down. I recently added the 200 # front springs. I noticed at Thunderhill Sunday that the rear seems a little "loose". While I plan on replacing many of the suspension bushings this summer, I am also thinking of replacing the stock rear torsion bars w/25.5 mm bars. And when I change out the bars, I was thinking of lowering the rear some more... My question is...will the 25.5 mm bars stiffen up the rear and if it makes sense, how far to lower?? Thanks for your advice!!

-CKKrause

M758

924S and 944 like to be level front to rear for gool balance. How far to lower? Not sure depends on how far off level you are. the 25.5 mm t-bars will stiffen the car, but not by much. 50lbs increase from 23.5 to 25.5. The good thing is that this is good match for the 60lbs increase from the stock 140 lbs springs.

Do remember that car balance is also impacted by alignment, tire pressure and driving style. Saying the car is "loose" does not mean that much without understanding much more that just spring rates. In general the 25.5 bars are good way to go, but should add oversteer making the car more "loose", However your loose condition may be caused by aligment rather than spring rates so I can't say for sure what will happen to the balance when you swap the t-bars.

ckkrause

Thanks for your response! I guess what I meant by loose rear end is that in a tight turn the inside rear wheel would lift and spin, so I'm trying to correct that I know, I know, slow in, fast out, but it really seems I have to go too slow to ...alignment is stock toe in and 1.9 front and 1.5 rear neg. camber.

-CKKrause

jim944s2

I've got an '89 944S2 upgraded to M030 spec front suspension (ajustable yellow konis all around), which is a just a bit softer sprung than your front. I had the car for about 2 years that way, including 2 seasons of auto-x. Last spring I added the 25.5mm torsion bars. It is a very nice improvement, it noticeably stiffens up the back end in hard corners and just seems more balanced, I think it is well worth doing (if you can do it for not too much $$!). It was very good before, and it's a bit better now.
I don't have lsd either (waiting for the right deal) and the stiffer torsion bars do help with the inside tire wheelspin.
Like said above, I think similarly low front and rear is good, there's a little bit of 'wiggle room', it doesn't have to be exactly even to be a nice drive.

M758

Is this on corner entry or corner exit.

Robby

As always.... great advice from M758... How have you been man? I haven't seen you in awhile....

Inb addition to this, I have to ask- when you say you are running HD's, are you referring to the AK1110-A & 1111-A Bils? IF so, you know that the valving for those shocks is set more to use ~300lb springs don't you? Not that this is cast in stone or anything- I would just like to know how it FEELS over bumps & such. I ALSO know your car is probably 100lb lighter than mine, so, that will make a dif- I like the look of the D-90s on that car... Do you have full manual steering? I'm trying to catch up w/a local 931 owner to drive HIS car & see how THAT feels before making my final decision on whether or not to delete.....

xsboost90

wow that pic looks familiar....

now i have the exact same set up on my car which is excellent for autox racing, but if your talking about de racing, you will want a slightly stiffer settup. Now w/ the 25 rear torsion, i would upgrade to some 250lb front springs. You could also try installing some rear coilovers and dropping some weight off of the rear torsions, some local guys have done that. TIFO? anyways.

My car does excellent on the track but if im going very fast on say a large track sweeper it does nose down considerably. I would try bigger springs, torsion upgrade and if its still loose, try adjusting tire pressures and keep it the same for awhile to get adjusted.

hrsteel

CKKrause, you say that the inside is lifting and spinning. Are you implying that it is coming off the ground? If so, you are defiantly droop-limited in the rear and reducing the rear ride height should help. If the inside is simply becoming less weighted than the outside, then that just means that you are turning. This can often be helped by moving the vehicle's roll stiffness bias forward, adjusting or changing the diff, or doing something different in the pedal-box.

xsboost90

the less weight is transferred forward, the more is on the rear. If you stiffen the front, as long as its not pushing, the rear will lift less. some say bigger sways..i say learn to transfer the weight correctly when you drive...and springs.

ckkrause

Thanks for all your replies...I have a lot to think about. However, a couple of comments/questions:

To M758- I guess the wheel lift is at the exit, more or less???

To xsboost90- How'd you get my car...I thought it was in the front!!!

To Robby- No, the shocks are basically upgraded stock, I like them alot, but they are not race oriented...

To Hrsteel- The wheel comes off the ground and spins up. I know that part of it is my driving...getting weight transfer right, but it seems very sensitive... Also, I don't understand what- "This can often be helped by moving the vehicle's roll stiffness bias forward..." means?

-CKKrause

hrsteel

Moving a vehicle's roll stiffness bias forward means making the front end relatively stiffer in roll than the rear. Common examples are stiffening the front anti-roll bar, or softening the rear. You can also do it with adjustable springs, dampers, or roll-centers, depending on what adjustments you have on your car. As other posters pointed out, tire pressure is extremely important.

Your rear tires should never leave the ground during forward acceleration, no matter what your driving style is. If there is indeed air under your tire during exit, you really need to lower the rear and/or soften the rear anti-roll bar a bunch.

M758

Ok you really can't be getting wheel "Lift" at corner exit. If you are accelerating at corner exit then weight is being put to the back of the car. On corner entry you can get rear wheel lift.

What you are getting is not enough at traction on corner exit. You need to do the following.

Lower the back of the car. While stiffer rear springs will make this worse lowering the rear of the car will help. I think after you do that you will want to stiffen the rear to keep balance everywhere on the the track.

Suspenions are tough... What helps in one spot can make the car worse somewhere else.

.... Robby.... I have been right here all along....