Knock when I brake

RICKYSH11

MEMBER
2005 CADILLAC CTS
6 CYL
2WD
AUTOMATIC

I seem to experience a weird knock or clunk sound when I initially apply the brakes in my car. It only happens after I've started the engine and apply the brakes when driving. After I'm driving for a while it doesn't do it anymore. I have recently changed the brakes and rotors on the front of the car. Also experience some vibration when travelling at speeds over 55. I'm not sure if my tires would have something to do with that, they are low profile tires. So, what could be the possible cause of the clunk and the vibration and is it something that I could fix myself or should I refer to a shop?

Thursday, May 5th, 2011 AT 2:41 PM

1 Reply

CARADIODOC

MECHANIC
34,090 POSTS

A single clunk when braking is typically caused by a loose brake pad or caliper. A potential clue is you will get another single clunk when backing up and hitting the brakes, and again, once when you go forward. Most of the time it is not a serious problem. Check for loose caliper mounting bolts, a long mounting bolt that missed the threaded hole, (that can let the caliper lift up and hit the inside of the wheel), or broken mounting hardware. The metal backing plates of the pads are forced against the mounting knuckle when braking. Check that surface to see if grooves are worn into it. Your car is kind of new to expect that already unless it has really high mileage. Those grooves can create enough room for a pad to move enough to make a noise that you can hear.

Ball joints and tie rod ends should be inspected too since they can cause clunking noises, but if the noise just started when the brakes were replaced, logic would say that's the place to look.

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Thursday, May 5th, 2011 AT 3:49 PM