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Donny
Donny, ASE Certified Technician
Category: Car
Satisfied Customers: 828
Experience:  A.S.E. Master Technician, Over 25 years working in Chrysler dealers, Top tech DaimlerChrysler 1998
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The steering wheel shimmies when I brake. The ...

Customer Question

The steering wheel "shimmies" when I brake. The actual brakes are good. Do you think it could be alignment?
Submitted: 9 years ago.
Category: Car
Expert:  Donny replied 9 years ago.

Hello

The pads and rotors may look good, but it sounds like your brake rotors are out of round,out of round unless very extreme normally can not be seen by eye, if you are only felling the shimmy while applying the brakes then the root cause is most likely in the brakes, having the front suspension checked for loose or worn components is a good idea also since outer tie rod ends do tend to go bad a lot, but normally you will also fell a front end problem on acceleration and when turning, if the car has more then 30,000 miles on it the alignment should be checked as a maintenance item

How to check your brake rotors

Any servicing of the rotor requires extreme care to maintain the rotor within service tolerances to ensure proper brake action.

Excessive runout or wobble in a rotor can increase pedal travel due to piston knock-back. This increases guide pin sleeve wear due to the tendency of the caliper to follow the rotor wobble.

When diagnosing a brake noise or pulsation, the machined disc braking surface should be checked and inspected.

Measure rotor thickness at the center of the brake shoe contact surface. Replace the rotor if it is worn below minimum thickness or if machining the rotor will cause its thickness to fall below specifications.

CAUTION: Do not machine the rotor if it will cause the rotor to fall below minimum thickness.

Minimum thickness specifications are cast on the rotor's unmachined surface

Thickness variation in a rotor's braking surface can result in pedal pulsation, chatter and surge. This can also be caused by excessive runout in the rotor or the hub.

Rotor thickness variation measurements should be made in conjunction with measuring runout. Measure thickness of the brake rotor at 12 equal points around the rotor braking surface with a micrometer at a radius approximately 1 inch from edge of rotor If thickness measurements vary by more than 0.0005 inch, the rotor should refaced or replaced.

On-vehicle rotor runout is the combination of the individual runout of the hub face and the runout of the rotor. (The hub and rotor runouts are separable). To measure rotor runout on the vehicle, first remove the tire and wheel assembly. Reinstall the wheel mounting nuts on the studs, tightening the rotor to the hub. Mount the Dial Indicator, on steering arm. The dial indicator plunger should contact braking surface of rotor approximately one inch from outer edge of rotor Check lateral runout on both sides of the rotor, marking the low and high spots on both. Runout limits can be found in the table at the end of this brake rotor information.

If runout is in excess of the specification, check the lateral runout of the hub face. Before removing the rotor from the hub, place a chalk mark across both the rotor and the one wheel stud closest to where the high runout measurement was taken. This way, the original mounting spot of the rotor on the hub is indexed

Remove the rotor from the hub.

NOTE: Clean the hub face surface before checking runout. This provides a clean surface to get an accurate indicator reading.

Mount Dial Indicator to the steering knuckle. Position the indicator stem so it contacts the hub face near the outer diameter. Care must be taken to position stem outside of the stud circle, but inside of the chamfer on the hub rim

Hub runout should not exceed 0.0019 inch. If runout exceeds this specification, the hub must be replaced.

If the hub runout does not exceed this specification, install the rotor back on the hub, aligning the chalk marks on the rotor with a wheel mounting stud, two studs apart from the original stud Tighten nuts in the proper sequence and torque to specifications.

Recheck brake rotor runout to see if the runout is now within specifications.

If runout is not within specifications, reface or replace the brake rotor

I hope that this helps you

If you need more information just let me know

Thank you

Donny

Donny and 2 other Car Specialists are ready to help you
Customer: replied 9 years ago.
Both the pads & rotors have been replaced...
Expert:  Donny replied 9 years ago.

Hello

Was the problem there prior to the pads and rotors being replaced? or did it start after?

Donny

Customer: replied 9 years ago.
After....the whole car seems to be affected...You can feel it in the steering wheel & on the brake pedal...
Expert:  Donny replied 9 years ago.

Hello

Check the lug nuts and be sure that they were tightened

With out being able to see the car I would say that the new rotors are most likely defective, mis installed or wrong for your application, you should return to whoever did the brakes and tell them that this problem started after the brakes where done, they should correct the problem for you as long as it has not been more the 12 months or 12,000 miles, since the rotors where replaced you should ask them to not "cut" them, but to replace them again, since "cutting" them will lower their useful life span

Thank you

Donny