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'07 cobalt, 60K miles. No ABS or Traction Control. Electric power steering.

Doing slow turns in a parking lot, with mixed snow/ice/dry pavement, the steering wheel jumps around. Not a lot, but noticeable. AFAICT, this doesn't occur when turning on dry or uniformly slick/snowy surface (today, for instance).

Watching from behind while the car makes these turns, I can see the tires' direction angle abruptly change (jump) as they go between dry pavement and patches of ice.

I don't feel any play in the wheels, and the steering seems tight. The struts seem OK when I bounce them, and going over 2" blocks in the driveway. Regular road tires (not snows). Tread is OK, certainly legal, and wear doesn't appear to be unusual. I replaced the rack and steering shaft, and the control arm bushings last spring.

Any insight appreciated. Thanks.

Update, 1/9/18: After more careful inspection of the front tires, I decided the wear might be uneven after all. So, I adjusted the toe out by 1/2 turn on ea side. Conditions yesterday were right for the problem to occur, and it did not. I'll do more testing before calling this an answer.

  • I'm still thinking on this. That no one has answered makes me think that my 'facts' are wrong/incomplete. I'll do more testing, when the conditions are right. – George Dec 26 '17 at 13:22
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I think this is simply the tires reacting to the different levels of traction available on the mixed surface. Slip angles on the tires is going to be very different. On dry pavement going slowish when you turn the wheel the car changes direction and the angle of the front tires is generally aligned with the direction of travel - little to no slip angle. On snow and ice, you can turn the wheel and the car is not going to turn as sharply, it's going to understeer because the traction is limited. The wheels are turned, the car goes straight or turns less crisply. Potentially large slip angles.

Say you drive onto a dry patch from a snowy patch with the wheels turned. The wheel is going to jerk and recenter itself to the current direction of travel and level of traction and vice versa. Same thing would happen to some degree on sand or loose surfaces or transitioning from dirt/gravel to pavement.

If you want to learn more about slip angles and how the steering angle and direction of travel relate under different conditions, get a good instructional book on auto racing. It should have a LOT of information about slip angles, etc.

  • Thanks - that all seems plausible ... but, I've been driving here for 50 years, at least 25 with front-wheel drive, and this is the first I've seen this. (Or my memory is gone, which is also plausible.) – George Dec 26 '17 at 18:52

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