Oversteer Issues

Tidybuoy · 05-29-2007, 12:40 PM

I've had this problem for some time and it's really bugging me. The car has (what I think) is over-steer. It seems to barely wander when driving at low speeds (i.e., 40 mph). I would equate this to like driving an inboard/outboard boat where it can't drive in a straight line - it's always going left or right - but barely noticeable.

At highway speeds (70mph and up) it feels unsafe and twitchy.

I had the car aligned and the technician convinced me to leave the front end camber alone as it was "nearly" in spec but the car was not checked with any weight in the car (which I've learned that this should have been done).

The car has new Koni's, and the ball joints and tie rod joints are all good.

When looking at the car this weekend, I noticed that the front end has more negative camber than the rear (I may not have my terms right but I mean that the top of the tires is tilted in-wards).

I'm going to go back to an alignment shop but I am trying to educate myself first - any advice would be great. I've read the suspension page on clark's garage and that has helped. http://www.clarks-garage.com/pdf-manual/susp-15.pdf

I'm just wondering, should I be able to see the camber in the front wheels. It seems to me that if I can tell by looking, there's too much. Not to mention, it was aligned without any weight in the front seats.

Any suggestions?

Eldorado · 05-29-2007, 12:48 PM

my rear wheels tilt in from the top like you explain too.. not sure if this is the way it's supposed to be, or not... but that's the only thing my car has in common with your car in this respect, so i dont think it could be what is causing your problems..

optimusprime · 05-29-2007, 02:36 PM

I don't think I would describe that as oversteer... but anyway, does it always drift to one side or can it go to either side?

In my case, I had a slight drift to the right... I had both a steering rack seal issue and a wheel bearing issue, so I don't know specifically which was to blame, but fixing those solved the problem.

mjadair · 05-29-2007, 03:07 PM

You mentioned camber adjustment, but the toe-in could be out of adjustment. This would definitely make the car twitchy.

vanwyk4257 · vanwyk4257's Garage

+1 on the toe adjustment. Check the insides of your front tires, if they're wearing way more than the outsides (assuming lots of negative camber) your toe is way off. It will definitely make the car feel like it's wandering as the front tires fight for control over which direction the car will go.

AaronM · 05-29-2007, 05:54 PM

Lots of negative camber and too much toe plus wide tires can really make a car wander (your car is wandering, not oversteering).

With the alignment to factory spec, none of the wheels should tilt noticeably inward when the car is unloaded. They should look straight.

Dantilla · 05-30-2007, 05:27 AM

Yup- Not oversteer, just a weak on-center feel.

To oversimplify, a bit of toe out makes the car feel this way. Popular for autocrossing, as it makes the car turn very quickly. Toe in will make the car more stable, but less nimble.

Wide tires make this worse.

A proper alignment is all you need as long as your tires are the proper size, and your suspension is in good shape. Are your bushings worn out? If so, no alignment will help. The suspension can wiggle around on its own where it's not supposed to.

Hope this helps.

JustinL · 05-30-2007, 06:51 AM

I've noticed different tires also cause changes in wandering. When I had 255 kumho 712s on the front, my car would want to change lanes! Switching to Falken Azenis made that go away.

AaronM · 05-30-2007, 07:41 AM

Quote:

Originally posted by JustinL
I've noticed different tires also cause changes in wandering. When I had 255 kumho 712s on the front, my car would want to change lanes! Switching to Falken Azenis made that go away.

That's called tramlining and you're absolutely right that it varies from tire to tire depending on tread design. In general, the better a tire grips, the more it will tramline.

Tidybuoy · 05-30-2007, 10:20 AM

I'm going to take it back in for alignment soon. I'm looking for a different shop that will spend the time to get it right.

My tires are new so I can't see any wear at this time (bridgestone Potenza's). The toe was set to spec. I really think this is a camber issue. The front definately has more negative camber than the rear (and that's without my fat ass in the driver seat). The bushings all look good and the ball joints and tie-rod joints all look good. The car only has 21k miles on it.

I just put on new Koni's front & rear but that didn't make any difference as far as steering goes. When I said the car wanders, I meant that it doesn't track a perfectly straight line. It doesn't pull, it just dosen't hold a perfect straight line and will veer off very easily. It's much worse at high speed. If I go on a long freeway trip, I feel like I can't take my eyes off the road for a second - it's just not a comfortable feeling. My other cars have not felt this way. My 88 BMW is much better at high speeds, so is my 914. The 944 will practically change lanes if I think it.

Something's not right and I will keep trying until I get it perfect.

Aufenbahn · 05-30-2007, 01:08 PM

Does your steering spin back to center properly after a corner? Tne caster angle setting affects this also. Also any stiffness in the steering gear.

Tervuren · Tervuren's Garage

First, I'd jack the car up check if anything is loose. My left side tie rod into the steering rack was loose on BOTH my 944's, and my '85 I owned prior as well!. Weird...(Also both my 944's had lightly bent right front wheels as well)

Camber is not going to make it try and jump lanes like that.

Its possible you have weak dampers that are past their age, allowing the suspension to bounce up and down needlessly. As the suspension moves, the geometry moves. Combine it with anything else being loose, and it would wander a bit.

Again - first check if you have any play. Thats the first thing before you go and take it off to an alignment shop - as even if they set it up "right" if the wheel can wander, then it will still be a problem, as that "right" is not fixed correctly. If you have up/down and side/side ability to rotate the wheel, then your bearings are likely loose.

When I bought my '86 944, it was like you described, following every single groove in the road. The problem was the wheel bearings, left tie rod, and weak shocks combined. It was wayyy too jumpy at interstate speeds with all that wandering around the front suspension was doing.

JustinL · 05-30-2007, 01:38 PM

Quote:

Originally posted by Tervuren

Camber is not going to make it try and jump lanes like that.

Agreed, I change camber for autocross vs. street and I find there is little difference in the straight line stability.

Check toe and caster.

Tidybuoy · 05:05 PM

ok, sorry for the confusion. The car is not jumping lanes, it's just not pulling to center. It basically slowly wanders to the left or right side of a lane and requires the driver to be attentive.

At high speeds (70mph and up) it feels edgy - like I would never take my hand off the wheel, a slight bump and it turns.

At really high speeds (100 mph and up) my hand hurts from gripping the steering wheel. It requires 100% attention.

At super high speeds (120 mph and up). I wouldn't attempt it. The car feels like the slightest tap on the wheel would cause a sharp turn.

As far as other suspension components - the struts are brand new Koni's. The ball joints have absolutely no play. The tie rods are tight. Again, the car is like new with only 21k miles on it. I'm going to put in new brakes this weekend and I'll re-pack the front bearngs - we'll see if this changes anything.

Maybe I'm just complaining too much but I have read nothing but great things about the 944 but my 914 and old BMW 528e would blow the doors off this car. The 914, although slow, would out handle my 944 hands down. If I ever got over 100 mph, I would be able to do it without turning off the raido and telling the passenger to shut up. My point, the 944 is a very stressful drive at hight speeds and just dosen't feel right.

I'll take a few snap shots tomorrow and see if I can show the front end camber - it's definately seeable in person (we'll see if I can capture it on film).

AaronM · 05-30-2007, 10:17 PM

You mentioned Bridgestone Potenza tires. I have a set of Potenza RE750s on my 951 and they do have a tendency to tramline, but not as bad as you describe. I really agree with everyone who says that the ultimate culpret is the toe-in setting. The camber being off is just a good way for you to tell that the alignment is definitely not set to specs.

Tidybuoy · 05-31-2007, 09:55 AM

I took a couple of photos of the front wheels last night. Although the camber is definitely noticeable in the front - it doesn't show in the photos too well. One thing that I noticed...the driver side camber is definitely more than the passenger side & the car is sitting on a level surface. I'm sure the ultimate cure will be a proper alignment with all settings (toe & camber) set to factory specs.

I'm posting a couple of photos below but the photos don't show the camber issue very well:

Driver side:

Driver side again:

Driver side tilts more than passenger side

passenger side tilts much less than the dirver side