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Massive understeer 
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Rookie Driver

Joined: Jan 19, 2010
Posts: 89
Ok,

I really got to fix my understeer problem.

And the problem that I have is the following: I don't know what spring rate I have up front. They are on the since we bought it.

I do have torsion bars at the rear and I guess that they are not the smallest one and most probably not the biggest one either. Still, I don't know what they are.

The shocks are Koni yellows.

What spring rate do you recommend? And what lenght?

Thanks

Charles


Mon Aug 20, 2012 8:22 am
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Rookie Driver

Joined: Nov 27, 2009
Posts: 19
Stock setups are always set for under-steer due to insurance regulations. The most accurate way to check your spring/torsion bar rates is with a scale and a tape measure. Most front springs and all torsion bars are linear rate. Have a heavy friend push down on the corner of the car with a scale between him and the car. When you have reached an inch, check the scale. Check again at two inches just to make sure. Use the chart at the link below to find your rates and torsion bar size. Getting rid of under-steer is as easy as raising the rate on the rear end of the car (make it stiffer). The easy way is with a larger diameter sway bar. Try one size at a time, as they make a big difference. Changing the actual spring rate is easier said than done. The only way to do that and keep the ride height is to PROPERLY change the torsion bars ($$$) and/or index them lower and add coil overs (again $$$).

http://garage.ideola.com/dl-SpringRates.html


Mon Aug 20, 2012 12:13 pm
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Driver

Joined: Jan 13, 2010
Posts: 158
honestly i have a 944 spec race suspension setup and honestly love it and wouldn't change it. i can run up front without the expense and its forgiving enough to take a trip off the track without hurting anything. i run koni yellows with 350lb springs up front with 30mm solid torsion bars out back. make sure you don't have a tire pressure problem or bad gauge ive had that problem before and ruined a new set of tires and messed my up my awesome setup making adjustments that weren't needed, trying to solve the problem.


Wed Aug 22, 2012 7:14 am
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Rookie Driver

Joined: Jan 19, 2010
Posts: 89
Thanks Guy.

350 lbs springs seems to be the consensus... The problem is that I don't know what is the torsion size... but the front is way too stiffer compared to the rear. Or the other way around...

What sway bar are you using? I have the Taretts...

c.


Wed Aug 22, 2012 9:41 am
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Driver

Joined: Jan 13, 2010
Posts: 158
Can you elaborate on your under steer problem,is it on both left and rights,is it occurring at turn in, mid corner or corner out, is it in low speed or high speed corners?
If its understeering the front springs are too hard or the rears too soft making the cars front tires slide. you can measure the torsion bar, it may be the correct 30mm bar to match 350lb springs. I recently bought weltmeister sway bars all around and love them for quick handling adjustments at the track. Tarrett bars are pretty expensive (i couldnt afford them), i find it hard to believe whoever you bought your car from spent all that money on those sway bars without going to atleast a 30mm solid bar or 31 mm hollow bar, it just wouldn't make sense. Was the car a race car before or an autocross car? Have you tried softening up the front sway bar and tightening up the rear? honestly that can make light and day changes in car handling. Also check your camber settings, its ridiculously common for people to have waaaaaaaayyyy too much camber because they think itll make the car handle better, and their essentially only running on 3/4 of their tires when less would allow a full contact patch(especially common on the front right wheel). For my car and tires its surprising how little camber is correct and without data saying theirs a problem with it i wont change it. Im more inclined to think you have a sway bar,tire pressure, too much camber or even have the car toed in instead of neutral/slightly toe out (all depends on your driving comfort level toe out isnt for everybody) problem before a spring rate problem.


Thu Aug 23, 2012 7:34 am
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Rookie Driver

Joined: Jan 19, 2010
Posts: 89
It's a car that we bought from a fellow 944 cup racer in 2010. It was already prepared as a race car and had actually raced before we got it. Torsion size and spring rates were unknown. It came with a stock 26.8mm front sway bar, a weltmeister rear adjustable sway bar. It was plagged with understeer from the day we got it.

Shocks were done and we replaced them for this year with new Koni sports. Still lots of understeer. I replaced the sway bars (I had them in stock anyway) with the Tarretts. High speed understeer is under control. Low speed corners are a mess.

Explanation of the problem: slow turns - I have to brake more before entering the corner otherwise I just don't make the turn. It's the initial bite that is lacking, up until the apex. I can't reach the apex, the car wants to push off the track. As soon as I straighten the wheel (exit of the corner), the under steer gradually disappears and I can apply throttle. If I want to enter the car at the same speed as the car in front of me, braking at the same place, I start the steering input and the car just don't turn, and even if I lift the car hardly rotates. I have to brake more, then turn and try to reach the apex. So the under steer is there all along the turn.

Fast corners- like #8 at mosport, I have initial bite, although not a lot, then just before reaching the apex (mid corner) if I want to clip it, I have to modulate the throttle i.e. lift to rotate the car so I minimise the mid corner under steer. It works. Spoon at Calabogie: a bit of initial under steer but the dip makes the front end starting to bite before the apex then it straightens so quite manageable. Then 4 left (Calabogie), initial bite then it starts to drift away from the apex but you can let it slide wide a bit.

Mid speed corners are about the same as high speed ones.

Here is what I will try at Mt-Tremblant:

Front sway bar is already af the softest setting. I will also soften the front shocks (they are at the stiffest). Stiffen the rear sway bar and will work on the tire temps/alignment trackside to correct the camber and toe setings if necessary.

Next year, I'm removing the torsion and I'll go with a full coil-over set-up. Meanwhile, I work on it for the Mt-Tremblant race.

Thanks

c.


Thu Aug 23, 2012 9:16 am
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Driver

Joined: Jan 13, 2010
Posts: 158
yea if you have a race coming up and dont have time to check out the torsions id defiantly make sure my front sways are adjusted to their longest setting and rears to their shortest setting and make sure your camber and toe are right, with what your describing it almost sounds like you have camber issues and possibly toe.


Thu Aug 23, 2012 12:52 pm
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