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Old 06-18-2008, 03:56 PM
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bluebee bluebee is offline
Seek to understand,^Value
Location: San Jose, California
 
Join Date: Mar 2008
Posts: 21,523
Mein Auto: 02 BMW 525i M54 auto 130K
I think I have front brake pad deposition imprinting problems

Oh my, I never did sit down for the hours it would take to collate and annotate the hundreds of photos I took for the brake job ... but ... even worse ...

I now have the dreaded brake shudder (judder?) when slowing down at highway speeds using the front brake (doesn't happen when I pull up hard on the parking brake and the brake pedal doesn't seem to be vibrating ... just the steering wheel). The car doesn't pull to either side and I didn't hit anything ... well ... nothing that lived.

I'm reading about brake judder (shudder?) here and it seems that some people erroneously say rotors "warp" but the rest (like the Zeckhausen crew) affirm they generally do not warp - they highspot, particularly with the front vented rotors, as to warp would require the webs in between to deform.
http://www.stoptech.com/tech_info/wp...rakedisk.shtml

Apparently I now have uneven pad deposits caused by my pads pooping on my rotors. Probably from my poor braking technique (which I'm not even sure what that is). From reading, it seems the high spots overheat and create a really hard compound that doesn't wear as the rest of the rotor wears, leading to the vibration getting worse over time.

Serves me right for not following the brake pad bedding procedure exactly (I just went real fast and braked real hard a few times but never the 0.9Gs or so it takes for the ABS to kick in at 90mph or so).

Is there a way to 'rebed' the brake pads?

edit: luckily I re-found this BMW brake pad re-bedding procedure ... which I will try tonight (apparently at about 0.7Gs)
http://www.zeckhausen.com/bedding_in_brakes.htm

And there is a really good shudder/judder thread here ...
http://www.bimmerfest.com/forums/sho...=brake+shudder

Apparently, one "cure" is to rebed the pads to scrape the brake poop off the rotors; another cure would be to put really abrasive pads on the front calipers for a few days to scrape off the brake poop. I've learned the braking technique should be to stop hard, then let up, and not to leave the pedal down while rotors are hot.
http://www.zeckhausen.com/avoiding_brake_judder.htm

Last edited by bluebee; 06-18-2008 at 04:28 PM.
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