Bent Rim vs. Brake Pulsation: How to Tell

Does it shake all the time or only when braking?

If the vibration shows up while you are cruising and you are not touching the brake pedal, the cause is usually in the wheel and tire assembly: an out-of-balance tire, a bent rim, a tire with an internal defect, or a loose wheel. It often changes with speed, appearing in one range and easing in another.

If the car runs smooth until you press the brakes, and the pulsing is felt in the pedal or steering wheel only while slowing, the rotors are the more likely source. Their surface may vary in thickness or have uneven pad material deposited on it.

What does a bent rim feel like?

A bent rim usually causes a rhythmic wobble or shimmy that is present whether or not you brake. A pothole or curb strike is a common cause, and the vibration may start right after one.

• Steering wheel shimmy: more noticeable if the bent rim is on a front wheel; a rear wheel tends to be felt through the seat.
• Uneven tire wear: a rim that runs out of true can wear the tire in patches.
• Slow air loss: a bend near the edge of the rim can stop the tire from sealing fully.

A technician can mount the wheel on a balancer and measure how far the rim runs out sideways and up and down. Balancing weights cannot fix a rim that is physically out of round.

Is curb rash just cosmetic?

Often, yes. Scrapes on the outer face or lip that only mar the finish do not affect how the wheel works. What matters is how deep the damage goes and where it is.

Deep gouges, flattened areas, or damage on the inner barrel or on the edge where the tire seals are worth having inspected, especially if the tire loses air or the car vibrates after the contact. Cosmetic refinishing and straightening are generally specialist wheel-repair jobs, so ask what a technician recommends for your wheel.

Can a cracked rim be repaired safely?

A crack is different from a scrape. A cracked rim can fail without warning, so it should be inspected before further driving. Some cracks are not repairable, and when a wheel is cracked the safe answer is often replacement.

If you can see a crack, hear hissing, or the tire keeps losing air after a hard hit, do not keep driving on that wheel. Fit the spare if you have one, or have the car towed, and have the wheel inspected. A technician can inspect the wheel and tire assembly and check the rotors in the same visit, so you know which is causing the shake.