So I changed my wheels and tires (to 17" AMG splitspoke and Potenza RE950s) around Thanksgiving, and the low-speed "hop" I had for months disappeared. I attributed it to out-of-balance tires, since I did have a shimmy at speeds above 45 or so as well. Well........

After snow was forecast last week, I put my old wheels and tires (the factory 8-hole wheels and OEM Continentals that came on the car) back on for winter duty. I used a pneumatic jack and jackstands, and a torque wrench. I didn't check the pressure as I figured it would be adequately low for snow use after sitting in the garage for 2 months. I drove to work (city and highway) and the hop was back! Worse than before though, and now the whole car was shimmying and I could observe the hood ornament visibly moving side to side at low speeds. So, on Friday I got the tires balanced (I had already installed them in rotated order)

After balancing, no more bad shimmy at highway speeds, but THERE IS STILL A HOP! Why, don't know. Here is what I DO know:

1) The shop that installed my AMGs, I think, overtorqued the lugs and helped warp the rotors (or for some reason, I developed a shimmy when braking in succession after about 1k post-install)

2) I used to feel the car hopping at low speeds, but since the rotation it hops AND when I steer, the car gyrates from side to side. That tells me that, in all likelihood, if their is an offending wheel or tire, it was on the back and is now on the front, and best I can tell it is coming from the front-right.

3) This behavior got noticeably worse after the tires sat apart from the car for 2 months, though it is not NEW behavior, rather same problem, just worse

4) If a tire or wheel were out of balance, out of round, or bent, wouldn't the person balancing the tire notice the problem?

For the record, I have never hit anything to bend a rim, so if it is the rim, it's a Starmark-certified bent rim.

Oh, and when I presented this problem late last summer, the dealer said they could not duplicate it. HELP!

Boo hoo, my posts rarely get answered.

I must ask stupid questions.

If I though it was something obvious, I wouldn't have asked!

Will, by all means check the tire pressure and inflate them to the recommended pressures on the gas cap lid. Why would you reduce the tire pressure for driving in the snow? Adjusting the tire pressure may help the "hop' problem, but I would check for a bent wheel. The fact that your car was Starmarked doesn't guarantee that one or more wheels aren't bent.

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Fred Hoelzle

I already adjusted it to 35psi, which I have run for a while. Again, no conditions have changed, other than I put the wheels back on after a 2 month absence, and the problem was more pronounced than before.

Also, like I said, a bent wheel (or something to the effect of a defective wheel/tire combo) would be the obvious culprit, but I can't imagine a bent wheel getting progressively worse - it is what it is.

Don't feel bad. There aren't tons of 202 people on this site as far as I can tell. Then only thing I would advise is jack up each wheel one at a time and spin that tire and look for roundness. Usually this will tell a lot.

Mike

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1998 C230 330,000 miles (currently dead of second failed EIS, yours will fail too, turning you into the dealer's personal human cash machine)
1988 F150 144,000 miles (leaks all the colors of the rainbow)
Previous stars: 1981 Brava 210,000 miles, 1978 128 150,000 miles, 1977 B200 Van 175,000 miles, 1972 Vega (great, if rusty, car), 1972 Celica, 1986.5 Supra

Well, it's going in for service Monday, after a preliminary diagnosis by tech of a belt problmem in the tire.

Sounds logical to me, oscillating at low speeds and then going away above 35mph.

I didn't tell them I have some nice summer wheels and tires. I'd almost rather have a couple free oil changes with 0w40 than 2 new Continentals!