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Thread: Front brake problems

  1. #1
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    Front brake problems

    I have an 04 M3. It was purchased late 2018. Drove fine.

    I prepared it for SCCA Solo STU class competition. I had been using Ferodo DS2500 pads on E36 328i and M3 with great results. But, not so much with the 46 M3. In street driving, no issues. But in competition using DS2500s again, the brakes were heavy and both my co-driver and I were losing boost and could not invoke ABS on dry pavement. There are no issues with the booster as it holds vacuum for weeks when just sitting.

    Today, I pulled the calipers to resurface the rotors to bed the pads again. SURPRISE !!!!!!!!!!!!! After a full season literally hundreds of runs in local events, a couple of Pro Solos, Divisionals, a Tour, and Solo Nats, the front pads had only a millimeter or two of wear, while the rears were about 25% worn. And THAT seems BACKWARDS.

    The system has DOT4 fluid and has been bled a couple of times during the year. This leaves me with the conclusion of a master cylinder and/or proportioning valve issues. It would be nice to know how one could determine where the problem may be. Thoughts?

  2. #2
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    maybe someone swapped the front and rear brake circuits on the MC?

  3. #3
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    Quote Originally Posted by eacmen View Post
    maybe someone swapped the front and rear brake circuits on the MC?
    VERY doubtful. But, I will look.

  4. #4
    dworthy's Avatar
    dworthy is offline Wagon meister :) BMW Tech Expert
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    Check the drag and temp on the rotors after taking the car for a drive. You maybe looking at a dragging caliper(s). The rears will tend to wear less on these cars I have noticed, so being at 25% doesn't surprise me too much.
    Darin
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  5. #5
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    dworthy, the front pads are NOTE WEARING, even after a full season of autocross with two driver's.

    Turns out the master cylinder was bad. Found one on eBay out of an 06 M3 for less than $100 shipped WITH the vacuum booster. Swapped the master and all is good.

  6. #6
    dworthy's Avatar
    dworthy is offline Wagon meister :) BMW Tech Expert
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    Ah NOT Wearing, sorry I missed that as I thought the pads had only 1-2mm left.

    So yeah I am surprised that you didn't lock-up the rear wheels on every turn if the blockage was that great in the MC.
    Darin
    Current:
    16 220i Active Tourer Platinsilver MET (C08)/Dakota Black (PDSW), P7ACA, P7LDA, P7LHA, P9BDA, 6sp Manual - Wife's new toy!
    05 325it Electric Red(438)/Gray(N6TT) ZCW, ZSP 5sp Manual Back set cover, trunk mat, Euro Infra-Rot front windshield, and mud flaps! Mr. Wagon My new Winter car.
    05 M3 Imolarot II(405)/Gray(N5TT) ZCW, ZPP 6sp Manual C.F. Lip, CSL diffuser, SSK, Euro Infra-Rot front windshield and a trunk liner! Mr. Go_Fast Stored for the Winter
    Past:
    95 318is Montreal Blue Met (297)/Beige(K1SN) RIP, killed by an Idiot.
    84 M535i gray market Burgandy Rot Met/Black Leather Lowered by Intrax on bilies, poly everywhere, B&B cat back system, K&N, and a hitch! Da Beast - Still running w/400k+!
    91 316i euro Tizianrot/Gray cloth - E-36 w/M-40 RIP, but great on gas! Best was 38 MPG
    82 528i euro Saphire Blue Met/Blue Leather RIP
    79 525 euro Green/Green RIP
    79 318 Silver/Black - The first one that got it all started
    M-Flight Member

  7. #7
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    The front brakes were functional, but when used hard, the pedal felt like there was loss of boost, and actually the pedal was being pressed so hard that available was used up between solo elements.

    I may attempt to dissect the MC.

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