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Something I learned this morning about checking for straight wheels on an '02 Taurus

I should mention that this whole project started because the car had warped brake rotors that caused a very noticeable shimmy on braking. I had them turned by a professional brake shop.

I have always checked for bent or wobbly wheels by jacking a FWD car up in front and running it at low speed in low gear. I do rears the same way. Of course I set the parking brake for the fronts. Today I tried this test on an '02 Taurus with factory issued alloy wheels. Both front wheels appeared to have about 1/8" of wobble. I had noticed a twitch in the steering wheel at low speeds which became a vibration at road speeds. I figured it had a tire with a broken belt, which it did, but the wheels were what confused me. I put those same front wheels on the rear of the car, and rotated them by foot power. The wheels DID NOT wobble, but sure enough one of the tires did. I checked the rear tires and wheels the same way on the rear to prove that they were good. Then I mounted them on the front. I repeated the same bogus test by running the car on jack stands with the former rear tires up front. Sure enough, the wheels wobbled, but the tires looked good. Knowing that the wheels tested good on the rear, I left them there. The steering wheel twitch is gone. I substituted another tire for the one with the bad belt and put it on the rear since it’s a different brand.

So why do the wheels appear to have a wobble when spun on the front? The wheel bearings do not sound or feel bad. There is no play in the tie rods or ball joints. No lost motion in the CVs. Do I have an issue that I need to look into?

Check the hub flanges for rust. If the rotor doesn’t mount squarely onto the hub flange because of rust. that slight amount of rust can throw the runout of the rotor off. Then when you mount the wheel onto the rotor it throws the runout of the wheel off at the bead.

They make a special cleaning tool for the hub flanges to make sure the rotors mount squarely onto the flange. http://3mcollision.com/scotch-brite-roloc-brake-hub-cleaning-disc-kit-07547.html

Tester

I’ll have to check into the rust situation on Monday. It’s too hot to go back out there now. The thermomonster says 105°F. At least the A/C works well. I think I’ll drive it home.