M758

I use 350/30 so my ratio 297/330 = 0.90 = balanced NA, using your .85 front number

For A time I ran 350/28mm so 297/254 = 1.17 = too much understeer

924RACR

I'm running t-bars only; car is 2640lbs, 660# front springs, 34mm hollow rear bars, 19mm rear Cup Car swaybar, 23mm stock front swaybar. This puts me at 561/553 = 1.0 per the rating scale.

Car is good, stick is excellent on corner exit, exhibits corner-entry understeer. It also lifts the inside front on corner exit - got pics to prove it. I plan to rebalance the car to improve things for this season, as it's 2% rear-heavy. I plan to reset it to level, try to get that to work, or progress from there.

trackjunky

650# F/R with understeer and slight inside front elevation in tight corners. Just changed to 700# rear and will report back my findings.

Based on what I'm reading here, my next step should be to decrease the front rate to 600# and see what happens. Thoughts?

(GREAT thread!)

93 FireHawk 968

Dave,

I get slight lift with the front wheels when it's a tight turn and the opposite is extremely weighted. An example is turn 9, left off camber, at the Glen. Most photo's show my inside front lifting.

I belive my springs are 600 all around, Koni coilovers w/o torsion bars.

mikew968

Well...i might be more confused at this point!!! I will stiffen rear sway bar and see how things go and then if necesary go to 800 rears. I think style is a big factor here as well.

Mike

adrial

What I would really like to see is effective motion ratio's for the swaybars as well... that would help show the whole picture and allow us to equate say the 968 m030 to the weltmeister and get a feel for whats really going on.

Does anybody have that information? It's not really accurate to say a ratio of 1.1 understeers, but 1.5 works great without knowing the swaybars involved.

The general rule that I follow is to run ~20% softer in the rear and balance out the associated tendancy to understeer with a stiffer rear swaybar. The rule is really to go for 90% of your chassis frequency at the rear as compared to the front...for our car and ~500# springs it works out to 20% softer in the rear. Or a ratio of 1.2 to follow the above methodology.

The softer rear spring rate helps the rear put the power down on corner exit...which is obviously very important. The stiffer rear swaybar means that it is more sensitive to changes in drop link length, giving you a lot of control over the handling characteristics of the car with a quick adjustment. Swaybars and springrates is obviously only one aspect of your setup...damping and aero can help to fine tune the car.

Lifting a front wheel seems like a result of a relatively stiffer rear in roll as compared to the front. Softening the front will help keep the tire on the ground because now the wheel will be able to droop further (because it was able to compress the softer spring more in the first place when you put the car on the ground statically). Stiffening the rear will obviously help keep the front from lifting as much in the first place.

Hope that all made some sense...and was somewhat usefull.

timo944

I'm surprised that nobody had mentioned the sway bars. The way a sway bar works is to transfer spring force from one side of the car to act in the opposite direction on the other. So if you turn left, the sway bar transfers spring force to the right side of the car (the outside) by transfering that amount from the left side (the inside). If the bar is very stiff, the spring force on the inside wheel goes close to zero or even negative.

I'll bet the problem is too stiff sway bar. Many of the 944 bars I have seen are very stiff. You have two choices to limit body roll: stiff springs and soft bar(ideal) or soft springs and stiff bar (less than ideal).

Make sure your springs are about the same as the rear rate and use a softer sway bar. I use the Kokeln on full soft and it works well (although it's far too heavy).

timo

Larry Herman

I'm not sure that I understand what you have said here. You really need to pick your front springs to control the dive under braking, and the rear springs to control the squat under acceleration. By definition then, higher HP cars need stiffer rear springs. Then you select the proper swaybars to add additional roll stiffness, to reduce camber loss, and to tune the balance.

When I was setting up my Carrera, I ran 23 mm front T-bars and 28 mm rear with 225s & 245s. It was a good setup, but when I changed to 245s & 275s the car developed understeer when I picked up the throttle going through slower turns. Part of the problem was the additional grip of the rear tires, and the fact that the car was cornering a little harder. To counter that we went to 30mm rear T-bars and tightened up on the front sway bar. Viola, the balance was back. The stiffer rear t-bars kept the car from sitting down under acceleration, and the balance was restored with the front bar. As a side note, the car did not want to lift the front wheel as easily as it used to.

Skip Wolfe

Can someone double check my D1 (centerline of the control arm chassis pivot point to the ball joint), D2 (centerline of the control arm chassis pivot point to the hub face), and spring angle values - those were estimates from memory and somewhat suspect.

As far as the sway bars, I guess my take is that the overall balance should be set by the spring rates and then fine tuned with the sway bars. Consequently, with front and rear adjustable bars it really doesn't factor into the equation. However, with the 30mm M030 bars your are stuck with the one setting so at that point it does become a bigger factor.

Van

I too, use Kokeln sway bars. My front has the NASCAR splines on the ends -- and, in fact, I've gone with a lighter, softer bar than originally shipped by Kokeln.

Does anyone have pictures, or experience with open wheel cars? I've seen a few at races and car shows, and always marvled at seemingly small sway bars. Are they really small (in comparison with our street cars?) Or is it just an issue of low vehicle weight and a low center of gravity?

I assume there are formulas out there for sway bar calculations -- I'll see if I can find some.

Nader Fotouhi

This is a very interesting read. However, I caution those who are thinking about changing their suspension based on well they think somone else's set up works. The suspension set up should be looked at as a package for a specific driving style. It is shock valving or adjustbility, springs or t/b rate, sways, tires (size/type), and driving style or ability.

AFAIK, I have never experience wheel lift on my stock S2 and run 25lbs lighter springs on the rear on Bilstein w/ virtually 0 rate t/b, 16" rims and 3250 with me in the car. Same set up gives me a very noticable corner entry understeer with 225 F/ 265 R tires compared with almost no understeer to a little tendency for mid-corner oversteer with 255 on all 4. Adding a stock LSD made the car understeer with 255 on all 4. BTW, I am probably a mid pack driver.

Nader Fotouhi

I have heard of many shops that use high spring rates to control roll and a light sway for fine adjustment.

Larry Herman

<==== BINGO!

Van

I've been doing a little sway bar research at my favorite place -- Wikipedia (http://en.wikipedia.org/wiki/Sway_bar), and came across this:

Wouldn't it be cool if there was some handy-dandy formula: as spring rates to car wight ratio increases by value X, the the sway bar's torsional rate should decrease by value Y.

RedlineMan

Confusing...

An entire page-and-a-half filled with questions that I offered answers to in post #12. Read a lot of the questions after that post, and then re-read #12. Am I on everyone's ignore list?



On a track car;

- Springs control roll/squat (forward/lateral motion).
- Sways control F/R balance.

Sways work like any other restrictive device, when it comes to balance. They reduce resilience (grip) of one end of the car, the defacto result of which is that the other end then has more resilience (grip), in relative terms. When you reach the point where the reduction in resilience (grip) that a sway bar causes becomes excessive, you need a stiffer spring, not more sway bar.

I offer that for the same reason you unhook sways when you corner balance, you should do the same to get a baseline for the balance of your chassis. If at this point you discover gross inadaquacies in the cars handling, you should be looking at springs (since they are the only thing there working, other than damping).

You'd ideally like to have it pretty close with the main component (springs) instead of relying on secondary components (sways, damping) to cover for larger abnormalities than they really should.