I've been getting a rotating grinding sound from my front brakes recently... especially from the front drivers side rotors. I took it to a shop to get it up on a hoist so that both them and me can take a look at the brakes.

The brakes pretty much look fine... the only thing we can see is a lip on the rotor. If you look at the outside edge... and close to the hub you can see a noticeable lip. The outside edge of the rotor also is rusty.

I can't think of anything else that could be causing the grinding noise... and neither can the mechanic. So we're thinking I need new front rotors.

Does this make sense to you guys? Can you think of anything else that may cause a grinding rotating sound?

And for those of you that are wondering what I mean by grinding rotating sound... imagine if as the wheel turns it's only rubbing at one point as the wheel turns.

 

I had something like that as well, it turned out to be the wheel bearing. The grinding sound on mine was more apparent when i was turning, but still there driving straight.

 

usually when you replace brake pads you should cut the rotors so the lips are not there or you should replace rotors also. The lip will cause noise like you describe. I work at Audi dealer and I usually recommend pads & rotors all the time.

 

This is often bits of rust from the outer edge of the rotor getting between the pad and rotor. Blow it all out with compressed air before you spend any money replacing things.

 

Wow.... thanks for the quick replies!

I sprayed the brake rotor and caliper area with a pressure water hose... and the sound almost completely went away. But then it came back later that day.

I'm not sure about machining the rotors as I can see the surface of the rotor is noticeably lower than before already. I asked a shop about cutting (machining) off the lip on the rotor... but they seem to think it's going to ruin the rotor considering the rotor already worn.

So I guess I need new rotors?

 

I was thinking about that... but as I paid closer attention to the sound I noticed it only happened while I was braking.

 

So assuming this is the rusty lip on the rotor that's causing the problem... this isn't a safety thing right... it's basically just an annoying sound? The car still seems to be stopping properly.

 

Stops good? Leave it alone.

 

Correct.

 

One of my rotors do the same thing that you've described. It sounds like only one part of the rotor is rubbing, so the sound oscillates (sp) as I come to a stop. There is no brake pedal vibration nor any less stopping power. But it's annoying as hell. Asked the dealer to take a look at it last month, but of course they didn't find anything wrong....

Per one of the previous posts, I'll definitely ask them to check if it could be a wheel bearing next time.

BTW, How many miles u got on yours and is it an MR with the 2 piece rotors or one piece rotors? I've got 10k miles on mines so i doubt the rotors are worn down much.

 

R the brake pads bedded? How many miles is the car?

This can happen when the pads aren't bedded to the rotors. Basically, ur pads r only making contact at a specific area. When bedded, the pads makes full contact and it also makes the rotor hug the pads more.

Another thing I can think of is that ur rotors warped...overtorqueing the lug nuts can do that. Even a minute amount of difference can be the rotors called warped. And from this, the brake guides...the thing that makes the brakes squeal when u need to change it...is making contact on the warped part of the rotor.

 

So basically your recommending if a car is making an obnoxious annoying sound but still functions to just ignore it? I couldn't disagree more.

If your rotors have rust, Recondition them as a start or sand any rust away from the areas where the pad contacts the rotor (you can also bevel the edges of the pad to avoid contact), if the rotors are to thin to recondition, replace them. There is no apparent rubbing issue of the calipers on the wheels it has to be related to the breaks or bearings, since your pressure washer reduced the noise, that eliminates the bearing as the culprit, leaving the brakes.

 

I just purchased a set of DBA5000 rotors... so I will install them with new pads once winter is over.

 

Check your dust shields, one might just be slightly bent and dragging.

 

guess I missed the part where the OP said "obnoxious annoying sound". This is only the 5th vehicle I've owned equipped with Brembos so I'm new to them and somehow got the idea that they will make some noise if you use them as intended and get them hot once in a while. I think I'll go back to the show and shine forum now.