Picking up inside rear wheel

[Off Camber]

Driving ITB Geo Prizm. I have a couple of issues I would like advise on. (however i think they are related)
1) Locking up right rear on breaking into right hand turns.
2) Picking up inside rear tire on turns.

This car has indipentent rear susp so I do not think it should be picking up the rear??
Also when I jack up the car the spirngs are no longer compressed and have quite a bit of verticle float. infact they drop off the spring purch.
I am running 3deg negative front camber 1/2 deg rear neg camber 1/8 toe out front and 0 toe on rear
It has carrera Coil overs
Spring rates??
It also has a real fancy rear sway bar with all sorts of adjustments on that I do not know anything about.

Any suggestions on set up or changes or spring rates would be appreciated.

Also the car is a little loose in the rear so I do not really want to change the balance of the car to much.

Appreciate the help and advice
Cheers SteveP

[Greg Amy]

Ugh. Such setup discussions for unknown cars are pretty tough. However, I'll speak in generalities...



1) Locking up right rear on breaking into right hand turns.
2) Picking up inside rear tire on turns.
[/b]

No doubt related.

First, a front-wheel-drive car picking up a rear tire is No Big Thang. They do that. The 'problem' is that the chassis is rolling over such that the available droop you have in the rear is exceeded. It is further exacerbated by the fact you have a rear sway (which you'll need) which is lifting the inside rear tire because the outside rear tire is being pushed up. That's simply the nature of the beast.

The only way to keep the inside rear tire from lifting is by increasing rollstiffness through springs and/or swaybars.

As for the brake lockup, unless that rear tire is on the ground it's gonna lock. You could add independent rear bias adjusters to compensate for it, or simply not worry about it.


Also when I jack up the car the spirngs are no longer compressed and...drop off the spring purch.[/b]

I think you'd find if you could see it on the track that the springs are staying in place while on the track. Rmember, you have a swaybar that is pushing up on the inside rear wheel; if it's of any significant stiffness it's pushing up on the inside suspension pretty hard, keeping the spring in place.


It also has a real fancy rear sway bar with all sorts of adjustments on that I do not know anything about.[/b]

Time to go looking for some good books on suspension setup.


Also the car is a little loose in the rear so I do not really want to change the balance of the car to much.[/b]

GENERALLY SPEAKING, if you add some spring rate it will cure an oversteering condition as well as go a long way towards reducing body roll (and, thus, rear tire pickup)...

[evanwebb]

When Greg is speaking about adding spring rate or increasing roll stiffness he is talking about the front, by the way.

In the rear the inside wheel is lifting because the roll rate (which is a combination of sway bar rate plus spring rate at that end of the car, in this case the rear) is high enough that all of the weight in the rear is transferring to the outside wheel, hence picking the inside tire completely off the ground.

As far as your fancy adjustable rear sway bar, I'll bet it just has a means of lengthening or shortening the effective length of the "arms" either by some arrangement of holes in the arms that the end links bolt through, or perhaps by sliding or twisting arrangement. In any case, you could try making the arms effectively longeror less stiff, thus reducing the effectiveness of the sway bar and hence the rear roll rate. It might make the car a bit les twitchy and save you having to buy stiffer springs for the front of the car. That is, to make the sway bar less stiff, try moving one or both of the end links further out on the arms.

[Motor City Hamilton]

Steve - Did you see how much my car did the "dog pissing on the hydrant" this past weekend. It's just a product of front wheel drive. You'll want less rear traction anyway - and what better way than to lift one tire right off the ground. Didn't that car come from Kristian Smith? He's a national level SCCA racer. I'd be hitting him up for advice any chance I got. Feel free to stop over at my paddock anytime you want to bench race and talk about car handling. That's the one thing I seem to be able to get right. If I could only get some more motor! :rolleyes:

I'm not sure why my car doesn't do the tire smoke thing in the braking zones, from the inside rear. I'd be that I'm not on the brakes as much and carrying more corner speed into turn 1 and 6. I'll look at my in-car video. I had to start from the back twice this weekend because of motor issues. I'll look at my closing speed if I passed you in 1 or 6. Plus, when my carb issue occurred on Sunday morning, the video was still taping while my car sat behind the corner station in 6. I think it captured you guys going through the braking zone so you'd have a good out-of-the-car look at what's really happening. I love to talk about car set up stuff. Like I said, stop by anytime. I can recommend a couple of books. Not much out there on front wheel drive.

Oh... and I think I'd like to buy the fuel cell you have for sale. Let me know.

Keith Hamilton
810-610-6050 cell
[email protected]

[Rabbit07]

Steve,

That car was fast when Dick Cole had it and it was fast when Kris drove it. Don't touch it! Learn to drive it and use a softer rear brake pad.

A loose car is a fast car!


Chris Childs
ITA 07 Neon

[Off Camber]

Thanks for the advice guys.
It was actually Dick COle who suggested I do something to stop picking up the rear wheel I think the break lock up is also breaking style. It did it a lot with me at first but less now I am used to the car. I let someone else drive the car in the feature on Sunday and that is when I saw th elock up again.

Thanks for all the suggestions.

SteveP