How to indentify a bent rim? [Archive] - SaabCentral Forums

: How to indentify a bent rim?

3rd December 2006, 12:04 PM
I have a shimmy in my steering wheel which seems to be related to a bent rim.
I'd like to replace it, what is the best way to identify the bent rim?

3rd December 2006, 01:13 PM
To start, just measure the diameter in various directions without taking the wheel off. If it is uniform all around the wheel, take the wheel off and measure the backside.

While you are doing this look for any clean areas which might suggest a wheel balancing weight has come off.

If all this checks out OK, just go to a wheel place and ask them to balance the wheel for you. You could probably get all 4 wheels balanced and rotated for $40 or so. Tell the servcie attendant you think a wheel might be bent. If one of the wheels takes an unusually large amount of weight to balance, it may be bent. A really bad wheel will not balance.

3rd December 2006, 01:17 PM
Hi ctrlz,

Thanks for your advice. The funny thing is that I believe that the installer bent my rim while putting on new tires this summer. I had them rebalance them because I noticed the shimmy, it did not solve the problem. So I had the Saab dealer try to balance them and they said that one of my rims was bent.

Is it possible for an installer to bend your rim? I noticed they scuffed a few areas on the front side of the rim as well, and I never had a shimmy until the day I drove off with the new tires.

3rd December 2006, 02:14 PM
I think it would be relatively easy to bend a wheel if it was dropped the right way without a tire on it. Some alloys are stronger than others.

I suppose you could also bend it on a tire mounting machine if the center hub wasn't clamped tightly while you were using the machine. I haven't used one of those machines in about 20 years, but I doubt much has changed. Those machines are mercilessly strong.

A good wheel and tire should balance up in three spins or less. And by the third spin you should be adding very little weight (like 0.25 oz.). If by the third spin it is still calling for 3 oz. somewhere, chances are the rim is bent. This is based on my experience with a computerized Coates balancer which was state-of-the-art in 1983. From what I can see in tire shops these days, not much has changed with these balancers.

3rd December 2006, 02:19 PM
TBH It's far more likely the shop's wheel balancer is out of spec. They need to be regularly calibrated.

The chances of bending a rim whilst fitting a tyre are very slim.

If you really want to prove it, swap the front wheels and rear wheels over. Back-> Front and vice versa. You should notice the steering wheel vibration stop and you may feel a rattle/vibration through the entire car body.

If you do feel a vibration, swap each wheel with the spare one at a time until the problem goes away. Then get that wheel balanced by a different shop. If this shop has trouble balancing it, they will confirm that it is bent.

Having said that, it is also perfectly possible to have a bent rim balanced and it won't give you vibration.

It's a difficult one, but don't look for the expensive option your dealer seems to have done. :roll:

3rd December 2006, 02:24 PM
Having said that, it is also perfectly possible to have a bent rim balanced and it won't give you vibration.

Provided it's not too bad.

3rd December 2006, 05:34 PM
I put on my winter wheels this afternoon, I took off what I suspected to be the offending "bent" wheel. I compared the weights to the other tires and it was missing the outer weight! I'm guessing the Saab dealership either did not balance my tires or they lied to my face regarding having un-balanceable wheel.

Thanks for your help guys I will take it to another shop to have it rebalanced.