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I have a 2002 Buick LA Saber Custom car. I replaced my rotors last year and just put new brakes on it. Now when I put brakes on to stop it makes a loud humming noise from both back wheels. I have checked everything, even roughed up the rotors, but it still does it.

Any ideas how to stop it?

  • Assuming the humming is similar to what you'd hear going over a rumble strip, it could be a bad wheel bearing, that has nothing to do with the rotor replacement. Or, it could have EVERYTHING to do with the rotor replacement. If your disc run-out (how straight the disc is) is out of whack, or if your brake rotor had a bit of dirt between it and the wheel hub, it's possible that the wheel bearing has been knackered due to unnatural pressure being applied in a poor angle. I'd reckon that's the noise. Raise the car and shake the wheel from 12 and 6 o'clock positions. Is there any play? – yollooool Jan 26 '18 at 19:26
  • ^^ By wheel, I mean the rear wheels. It should be nice and tight with no vibration or play (it shouldn't move around at all.) If there is play, it's either a wheel bearing or some other suspension component that's not quite happy. Usually, a wheel bearing you'd hear constantly, but I've known it to happen only whilst braking, as the wheel bearing is under a lot of stress with the brake caliper clamping on one side of the rotor, which would cause some 'OutPush'. Because the wheel is spinning with the weight of the car and the caliper is trying to stop it, it will try it's hardest to stop it. – yollooool Jan 26 '18 at 19:28
  • This is a less likely cause, but pads or anti-rattle/squeel plates of the wrong kind, or aftermarket ones, may also cause your hum. By the way, how did you rough up the rotors?.. – Bart Jan 26 '18 at 20:36
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I know this is a 5-month old question but someone might benefit from my answer so here it goes.

I have a 2006 Mazda 3 that had the same problem right after I replaced the rear brake pads but retained the original rotors. After about a week, it developed a humming noise at low speeds, similar to the sound when you rub a wet finger on the rim of a wine glass. At times, it seemed like there were trumpets in back of the car and it can get quite annoying and embarrassing when going out of the parking area. The noise goes away though at speeds above 20 MPH.

After a thorough inspection, I noticed that my rear rotors developed a slight lip at the inner and outer edges. The noise is caused when the edges of the inner brake pads hit the lips of the rotors. The replacement Bendix brand pads that I used had a clip system for the inner pads instead of having springs on top, as with my original Mazda brake pads. Unfortunately, the clips do not do a good job of holding the inner pads well in place thus after some running, the edges of the pads hit the lips of the rotors and the resulting noise.

To fix this, you might need to get OEM style brake pads (same type as your original pads). I got a new set of brake pads (Bosch) that looked the same as the original Mazda pads, ones with the spring on top and the noise went away.

In case replacement with the correct pads still does not work or if the noise comes back, then you need to get new rotors or have your current rotors resurfaced, granted the thickness is still within standards.

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