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BMW 3-Series (E90 E92) Forum > E90 / E92 / E93 3-series Technical Forums > Suspension | Brakes | Chassis > J brake sound/slight shaking occasionally from pedal?



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      07-18-2013, 01:56 PM   #1
my07_335i
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J brake sound/slight shaking occasionally from pedal?

My front brakes have 44k miles left before changing, rears are at 14k, according to car. I replaced both the rotors, pads, and fluid last time i did my brakes, around 10 months ago. Within the last few months, I've occasionally (maybe a few times a day) where when I brake around 60Mph, the pedal vibrates slightly, and I can hear what sorta sounds like a truck using it's J brake (coming down hill), but it's not loud, and it sounds like it's coming from the center of the car (maybe slightly from the rear).

My first thoughts, either the pads/rotors are warped/unevenly worn, or maybe theres air bubbles in the brake lines? I was careful when bleeding to get all air out, but maybe one bubble or something remains... I don't know.

I'm getting ready to replace the rears again, but wondering whats causing this.

Any thoughts?
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      07-18-2013, 02:03 PM   #2
Red_Bean_Bun
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Air bubbles would make squishy pedal feel.

You can re-bed the pads.

It's the rotors that I would suspect that might have warped.
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      07-18-2013, 03:31 PM   #3
bhmax16
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Did you do front and rear brakes last time you did them or just one or the other?

Air in the lines will not cause this issue. It will cause a squishy pedal like Red Bean said, but not any type of noise or vibration.

Vibration in your pedal is a telltale sign of warped rotors. What type of pads and rotors did you use for replacements? Did you break them in correctly after the brake job? You should avoid hard braking when the pads/rotors are new and go easy on them for the first 100 miles or so, especially in the rain.
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      08-14-2013, 07:59 PM   #4
my07_335i
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Quote:
Originally Posted by bhmax16 View Post
Did you do front and rear brakes last time you did them or just one or the other?

Air in the lines will not cause this issue. It will cause a squishy pedal like Red Bean said, but not any type of noise or vibration.

Vibration in your pedal is a telltale sign of warped rotors. What type of pads and rotors did you use for replacements? Did you break them in correctly after the brake job? You should avoid hard braking when the pads/rotors are new and go easy on them for the first 100 miles or so, especially in the rain.

Winner! just got new rotors/pads in for the rear, swapped them out, no more vibration. I had previously broke them in, doing a 60-10mph set about 10 times, after having warmed them up by slow braking from 60-30 for a minute or two.

The rotors had a lifetime warranty against warping, I bought a thickness guage to try and measure various points on the rotor to see if it indeed warped.

Thanks guys!
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      08-15-2013, 10:39 AM   #5
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Quote:
Originally Posted by my07_335i View Post
Winner! just got new rotors/pads in for the rear, swapped them out, no more vibration. I had previously broke them in, doing a 60-10mph set about 10 times, after having warmed them up by slow braking from 60-30 for a minute or two.

The rotors had a lifetime warranty against warping, I bought a thickness guage to try and measure various points on the rotor to see if it indeed warped.

Thanks guys!
I like being the winner Glad you got it sorted out. In the future, I'd suggest breaking the pads in doing a 45mph-15mph routine for 10-15 times, then after get on a road with no traffic or stop signs/lights where you can cruise at a steady speed for 5-10 minutes to allow the rotors to cool back down. Slowing down from 60mph during the initial breakin seems a bit excessive and may have contributed to the premature warpage of the rotors.
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