Think I need suspension help, rear end keeps coming around Options

[turboman808]

I just got back from the autox. I am a bit disapointed. Now I am definetly very new to the car but this just doesn't seem right. To me it seems that the rear comes out or over steers just way to easy. A slight blip of the throttle and out it goes. Quick transitions thru the slaloms also does it.

Did put larger width rear tires on and figured that would solve it. I also stiffened the front sway bar a bit. Although I am starting to wonder if that was right or not.

At this point what would be the best wat to remedy this. Stiffer rear springs? Lower front or lower rear? Add a rear sway bar? Begining to think I just don't understand mid engine rear drive setups (IMG:style_emoticons/default/blink.gif)

I'm kinda leaning towards lowering the front a 1/2 inch but want to here some opinions of people who actualy know what they are doing.

[nebreitling]

choke up on that front sway bar even more.

in general:

tighten the front = make rear stick
tighten the rear = make front stick

what's your setup? (spring rates, tire sizes, torsion bars, sways, etc.)

[Trekkor]

Yes, more info on your total set-up, including tire brand and pressures.

KT

[turboman808]

bridestone potenza s02a front are brand new rear are just about to the wear bar

17x7 205/50
17x9 255/40

bilstein shocks

weltmeister front sway bar and no rear sway bar.

I'll have to get under the car to see what the torsion bar and springs are.

[ConeDodger]

bridestone potenza s02a front are brand new rear are just about to the wear bar

17x7 205/50
17x9 255/40

bilstein shocks

weltmeister front sway bar and no rear sway bar.

I'll have to get under the car to see what the torsion bar and springs are.

Well, you don't talk about tire pressures but it could be that the worn rear tires are just about done giving lateral grip. The 17X9 225/40 profile tire has almost no sidewall to flex which is one way of absorbing the lateral g force.

A rear sway bar will make this worse.

I would suggest some tire pressure changes but what you are describing is happening much too easily. Just how much power are you packing? Your screen name implies turbo. Is it even a type 4 or a Porsche 6?

More information needed.

[turboman808]

a 6 with 240hp 190 lbs torque

The tire pressure is 31 all around

[Trekkor]

True on power.

I had to learn how to drive all over again after the SIX went in.
I was experiencing "snap oversteer" out of corners where I was driving flatfooted with the FOUR.


KT

[ConeDodger]

a 6 with 240hp 190 lbs torque

The tire pressure is 31 all around

Wow... You must be one happy guy. Given what you have just said, I would say you need better tires (not worn) and more negative camber.
Negative camber will cause the tire to flatten out and stick in corners.
I would start with new rear tires and then have a four wheel alignment and corner weight done and get as much negative camber as you can in the front and rear. Usually we are talking about 2 to 2.5 degrees. Not counting the tires this should be around + or - $200.00 With the right settings the car should feel like it is connected to your brain synapses. You think turn and the car does it.

Just a thought here, I have no experience with those tires but I believe them to not be R rated DOT tires. Given that, those pressures seem a little low. 35 - 40 would seem more in the autocross ballpark.

You have got a lot of power for a 2000# car. I bet you are just overwhelming your grip.
Given your power to weight ratio, I think the simpler solutions like those involving tire pressure are going to be too little for you.

[Trekkor]

Rob gives you good advice. (IMG:style_emoticons/default/clap56.gif)

You will need to modulate throttle in and out of the turns.
Once you straighten the car out, then GO!


KT

[Thorshammer]

would you pm me your suspension set up, and I agree that some gentle throttle application may help. But with that amount of rubber on the road, I really doubt the oversteer problem is ALL throttle application.

Erik Madsen

[turboman808]

I have it around 2 degrees in the front. The back I don't know how to adjust but you are probably right there. I'm gonna order some new rear tires tonight. Some falkens since I have been happy with them in the past.


I would really like to give more setup information but I just don't know the car that well.

Any links to how to adjust the rear camber?

[ConeDodger]

would you pm me your suspension set up, and I agree that some gentle throttle application may help. But with that amount of rubber on the road, I really doubt the oversteer problem is ALL throttle application.

Erik Madsen

Erik is right. That is a lot of tire. I am just thinking that the combo of worn tire and high power to weight ratio is going to cause the snap oversteer. You should be able to get at least 2 degrees negative out of the back with yours. I got it in mine without any tricks or spacer magic.

[ConeDodger]

I have it around 2 degrees in the front. The back I don't know how to adjust but you are probably right there. I'm gonna order some new rear tires tonight. Some falkens since I have been happy with them in the past.


I would really like to give more setup information but I just don't know the car that well.

Any links to how to adjust the rear camber?

I have Falkens on my 240Z. I know of lots of guys autocrossing with them in SCCA. Temperature is an issue. These tires do not like getting hot. They can lose their grip when hot. A trick I see the SCCA guys using is a pump water spray after each run to cool them.

[ConeDodger]

Rob gives you good advice. (IMG:style_emoticons/default/clap56.gif)

You will need to modulate throttle in and out of the turns.
Once you straighten the car out, then GO!


KT

Trekkor,

I cannot wait to autocross the Bumble Bee. I am going to embarrass the snot out of myself spinning around and around!!!

I think I will bring the 4 to your party next week though... Depends on the good Doctor at IPB and what his prognosis is after the Bumble Bee tune, valve adjust, and weber adjustment... If he says the Bee can fly, who am I to keep her down?

[sww914]

You adjust the rear camber by adding shims to the trailing arm end cap to decrease neg. camber, and you remove shims to increase neg. camber.
This is the end cap behind the rocker cover, with 3 bolts in it, pointing up towards the sky. The toe is adjusted in the same place, by prying the cap forward for more toe in, and towards the back of the car for toe out.
If you have the proper shims, you only need to remove one bolt to add or remove shims, the other 2 holes in the shims are slotted.

[Joe Ricard]

Yea tires. you would have problems with any street tire and that much horspower.
However learning how to drive the car (no offense) but braking in a straight line and mashing the gas when you are pointed right is very important.
Also to keep the rear planted to the surface through judicious applications of throttle. Acceleration will transfer weight to the rear and make the rear tires stick.

[ConeDodger]

Yea tires. you would have problems with any street tire and that much horspower.
However learning how to drive the car (no offense) but braking in a straight line and mashing the gas when you are pointed right is very important.
Also to keep the rear planted to the surface through judicious applications of throttle. Acceleration will transfer weight to the rear and make the rear tires stick.

Joe speaks volumes! You may need to slow down to go faster. Momentum momentum momentum!

[john rogers]

Couple of things to consider, do you have a limited slip, if not with that much power one wheel can't handle it well. When I was auto-xing with the six I ran about 24 to 25# air pressure cold front and rear. Many of the 914s I see use same size front and rear tires as the larger rear tires will force oversteer. Whenever I replaced tires for racing, I replaced all 4 at one time so tire wear as a factor is eliminated.

[turboman808]

Thanks for the replys. I am more then a bit disapointed so far. But I will get it sorted out. I'm gonna stiffen the front sway a bit more, add more camber to the rear and ordered new rear tires but they won't be here until next week I am sure.

I'm also gonna take a driving course this friday and hopefully get some of it all sorted out. This time I will bring the tire temperature gauge with me and adjust pressure where needed

[turboman808]

Couple of things to consider, do you have a limited slip, if not with that much power one wheel can't handle it well. When I was auto-xing with the six I ran about 24 to 25# air pressure cold front and rear. Many of the 914s I see use same size front and rear tires as the larger rear tires will force oversteer. Whenever I replaced tires for racing, I replaced all 4 at one time so tire wear as a factor is eliminated.

So your saying the larger rear tires force it into a spin HUH? I could kinda see that. I swear though I feel like I am barely touching the throttle.


Yeah I just picked up the wheels on ebay and this is how they came. I've only put a few hundred miles on the front which were brand new. The rear definetly need to be replaced soon.