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Thread: Brake Shoe Position on Brake Cylinder

  1. #1
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    Brake Shoe Position on Brake Cylinder

    I noticed the rear most brake shoe appeared to be about to slip off the brake cylinder while preparing my car for its MOT test:



    The front shoe is positioned centrally on the piston:



    The brake assembly looks like this:



    I have checked these two threads:

    http://www.a2oc.net/forum/showthread...ght=rear+brake

    http://www.a2oc.net/forum/showthread...535#post203535

    The only thing I have noticed is that there is a lip on one edge of the cylinder in front of the shoe. Should this be behind the shoe? Any advice appreciated.
    Last edited by philward; 10-06-2017 at 11:50 AM.

  2. #2
    Quote Originally Posted by philward View Post
    I noticed the rear most brake shoe appeared to be about to slip off the brake cylinder while preparing my car for its MOT test:



    The front shoe is positioned centrally on the piston:



    The brake assembly looks like this:



    I have checked these two threads:

    http://www.a2oc.net/forum/showthread...ght=rear+brake

    http://www.a2oc.net/forum/showthread...535#post203535

    The only thing I have noticed is that there is a lip on one edge of the cylinder in front of the shoe. Should this be behind the shoe? Any advice appreciated.
    the lip on the cylinder piston should be in front of the shoe , there are two different cylnders /shoe sizes depending on model , if all parts are correct sizes (fairly obvious visually ) then common practice would be to unwind handbrake fully at rear of h/brake lever to fully release mechanism then if drum condition is good no lips, would be to then adjust shoes out so as the drum will spin freely when fitted but any more adjustment would cause a bind , once both sides have correct adjustment adjust h/brake again to a few notches , if all is correct then you should find the shoes will sit centrally on pistons ,

  3. 2 users that liked this post:

    kp 115 (10-06-2017), philward (12-06-2017)

  4. #3
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    Thanks Mark; that is exactly the procedure I apply on a classic mini. Never thought it was necessary on the VAG cars that I have owned as the rear drums and callipers have all been self-adjusting.

    To remove the drum I simply spring the adjusting wedge and the drum comes off easily.



    It goes back on easily and with two presses of the brake pedal the shoes are correctly adjusted. Would I be missing a trick somewhere? Also is the position of that shoe an issue?
    Last edited by philward; 12-06-2017 at 08:26 AM.

  5. #4
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    Quote Originally Posted by philward View Post
    Thanks Mark; that is exactly the procedure I apply on a classic mini. Never thought it was necessary on the VAG cars that I have owned as the rear drums and callipers have all been self-adjusting.

    To remove the drum I simply spring the adjusting wedge and the drum comes off easily.



    It goes back on easily and with two presses of the brake pedal the shoes are correctly adjusted. Would I be missing a trick somewhere? Also is the position of that shoe an issue?
    It is also worth checking that the little "buttons" are in place. The edges of the shoe sit against these and they look like little metal discs with a very short centre pin.

    These can fall out when working on the shoes and that would make the shoe sit closer to the backplate than it should be.

    Steve B

  6. Users that liked this post:

    philward (13-06-2017)

  7. #5
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    Thanks Steve, I started investigating because the rear brakes suddenly started making a scraping noise. They were full of dust so assumed this was the source of the noise.

    Not so; the scraping noise is still there and I now suspect it is the out of position shoe being applied against the small rough ring of drum on the inside (where a lip eventually forms). I’m now thinking something broke in use, also I did retrieve something looking like a white nylon washer when I cleaned the back plates. Any ideas? Could that be part of the pin?

  8. #6
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    As Steve suggested, the 'washer' is probably one of the Teflon slider pads which stop the shoes rubbing on the backplate.
    Ref the pic in this post (#5), looks like there should be 4 pads - http://www.a2oc.net/forum/showthread...440#post221440

    Cheers Spike
    Last edited by spike; 13-06-2017 at 09:41 AM.

  9. Users that liked this post:

    philward (14-06-2017)

  10. #7
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    Quote Originally Posted by philward View Post
    Thanks Steve, I started investigating because the rear brakes suddenly started making a scraping noise. They were full of dust so assumed this was the source of the noise.

    Not so; the scraping noise is still there and I now suspect it is the out of position shoe being applied against the small rough ring of drum on the inside (where a lip eventually forms). I’m now thinking something broke in use, also I did retrieve something looking like a white nylon washer when I cleaned the back plates. Any ideas? Could that be part of the pin?
    most certainly the white ptfe 'washer' is the remains of one of the 4 'pads' that the shoes slide against on the back plate
    Paul (Depronman)
    1.4 TDI 2001 287,347 miles and still going strong

  11. Users that liked this post:

    philward (14-06-2017)

  12. #8
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    Thanks Steve, Spike and Paul you are all correct, one of the buttons is worn through and the rear most shoe was resting on the back plate.



    Parts ordered including two new rear hub retaining nuts. Anybody know the correct torque for these nuts?

    I found this article useful http://faculty.ccp.edu/faculty/dreed...tech/reardrum/
    Last edited by philward; 18-06-2017 at 08:09 AM.

  13. #9
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    Well the new pads failed to correct matters. They are approximately 1mm thick so moved the shoe forwards by 1mm and so it still sits on the edge of the piston.

    Any suggestions? Perhaps a machining error on the cylinder????

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