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Do you need to improve your R100GS Rear Drum Brake? How?

Discussion in 'Airheads' started by Box'a'bits, May 5, 2011.

  1. Box'a'bits

    Box'a'bits In need of repair Supporter

    Joined:
    Sep 26, 2008
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    4,397
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    Wellington, New Zealand
    My rear brake shoes are OEM BMW shoes, of unknown age. Despite being scuffed up several times, they tend to glaze, & won't hold the weight of the bike on even a moderate hill.

    Cables are free, pivots etc are all in good condition.

    At present this means my braking is entirely reliant on the front brake, which I have already uprated to a 4 pot Tokico.

    Do you guys have (or have had) similar issues? How did you resolve these?

    I have considered replacing the shoes with EBC or Ferrodo shoes. What is the consensus on this? I know that there has been past discussion on the quality of some of the shoe castings, which suggested these didn't sit squarely on the drum. A further option is to get softer material bonded onto the OEM shoe castings.

    I need to improve things dramatically. Only having front brakes offroad can be 'interesting' at times, especially on steep loose downhills, slow speed situtaions, or when the bike is loaded.

    I am aware of Phreaky Phils upgrade to a rear disc. This is not a happening thing at present due to cost. I'd prefer to work with what I've got.

    Gratuitous vanity photo
    [​IMG]
    #1
  2. Lornce

    Lornce Lost In Place

    Joined:
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    Way Out There.
    What kind of oil are you running?


    :ear



    :lol3


    If you've got a truck brake shop nearby have them do your castings in the same material they use on tow-motors (forklift trucks). It's a popular mod with a few of the vintage racers here in Cannydah.

    :freaky
    #2
  3. StephenB

    StephenB G(/)S ... what else!

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    My advice: use it more often! My riding style supports using the rear brake always and the front brake occasionally. As a result, there is no glazing on the shoes (or pads for that matter), I can lock up the rear wheel anytime and can control it fairly well.

    YMMV

    Stephen
    #3
  4. Screaming Chicken

    Screaming Chicken Long timer

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    Miles do obviously vary. :-)

    I had this exact problem, rear brake useless, I could have the bike in neutral on level ground, stick my heel down hard on the brake pedal, and use my left foot to gently push the bike through it.

    I've since replaced the shoes with a new set that's been modified by Mat from Bmwboxersupplies, he recommended taking the last 2" or so of liner off the bottom shoe before mounting.

    That said & done, it's better, but still not much use for anything past stabilising things a bit in corners. It certainly won't lock the rear in street use. I guess my drum is just crap.
    #4
  5. Travelling Sam

    Travelling Sam Travelling Sam

    Joined:
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    Location:
    Exeter UK - Roman city, real ale, great riding...
    A soggy back brake is fine on the level or soft stuff - I actually found it to be an advantage but I know what you mean on the steeper slopes. Makes life interesting no : ) There is a mod that I've seen done which will hold a GS, two up with overlanding luggage, down hill on gravel. I think it was the guys who wrote the book 'Sorebums Across Asia' (good book by the way) Track 'em down. Tell 'em Sam says hi : ) Good luck.
    #5
  6. supershaft

    supershaft because I can

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    Have your shoes relined. So far from what I have heard, anything is better than what BMW used. The stuff is crap. It's rock hard. The shoes are so hard they wear out the drum and the shoe will still look almost new.
    #6
  7. Boxer Metal

    Boxer Metal Mad Scientist

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    The originally lining dries out with age. Replace them and be careful not to use an aggressive lining. It will eat the drum.
    #7
  8. Boxer Metal

    Boxer Metal Mad Scientist

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    I have to disagree. When they were new and fresh they worked very well.
    #8
  9. Stagehand

    Stagehand Imperfectionist

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    Never had a problem such as you speak of. I keep the pedal fairly tight though, so there's not much throw to actuate it. That might help you, if you get like two cm's of throw before it will lock the back when off the ground.
    #9
  10. Travelling Sam

    Travelling Sam Travelling Sam

    Joined:
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    Exeter UK - Roman city, real ale, great riding...
    I've found an email address for the Sore Bums guys. I've emailed them to ask if I can pass it on to you. Do you want to PM me and then if they respond with a yes, I can get streight back to you.
    It'd be great to know how you get on with the mod if you go for it.
    Cheers,
    Sam
    #10
  11. igormortis

    igormortis Cafe Reise

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    I’ve had several Airheads with rear drums of varying efficacy. Never liked the EBC shoes, but then I’ve had mixed results with BMW shoes also.

    I’ve had a mono with a drum brake that I could lock up at will, every time, solo. Add a pillion and some luggage and the pucker factor went up exponentially.

    And I’ve never been able to get any progressive action from the rear brake. It always seems to be drag, drag, drag, LOCK.

    I’d suggest getting some BMW shoes relined and see what you think. I was gonna bring a set in to the brake and clutch place in town (on St Martin’s Sq). I’ve seen some crazy projects in there before, so I’m sure they could help.

    Now I’m just gonna ditch them altogether... :evil
    #11
  12. Box'a'bits

    Box'a'bits In need of repair Supporter

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    Okay Igor, PM with your plan. R1100 swingarm, rear disc, or monolever. Personally I'd like the R1100 swingarm (because I like the idea of a paralever that has the bugs ironed out), but am not able to progress that just yet. :evil

    When do you want to have a go on the pivot pegs? Maybe we could swap rear brake shoes & you could have some real excitement in your life...

    EDIT. Never mind. I've seen Lornce's thread, where you talk about the R1100 swingarm conversion
    #12
  13. Box'a'bits

    Box'a'bits In need of repair Supporter

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    Thanks guys, sounds like my brakes are the exception rather than the rule. My past drum braked BMWs ('83 R80ST, '86 R65, '88 R100RS) have been monolevers, with 'adequate' rear brakes - I wasn't sure if this was a paralever foible. I was unwilling to pay out for new shoes if I was just going to have the same issue going forward.

    I was aware of others with Paralevers had the same issue with their rear brakes.

    I should also have stated that the bike has 200k+ kms on it, so the brake shoes could be real old. They are standard BMW shoes, but show little wear, and seem real hard. Could be just completely dried out.

    I'll try some new shoes, which will free the old shoes for a re-line if necessary. :wink:
    #13
  14. advNZer?

    advNZer? Long timer

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    my brakes have new shoes and they are much better but not stellar.I doubt i could lock it on the street.Ask Mike D
    #14
  15. Box'a'bits

    Box'a'bits In need of repair Supporter

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    I stopped to take this photo, was sitting astride the bike facing uphill, in gear, with the rear brake applied. Steep hill. The bike went chuff, as it went backward to hit compression. That'll help I thought. Nope. More chuff chuff, things are getting out of hand, hand back on the front brake, shit what do I do now....:huh
    [​IMG]
    #15
  16. Padmei

    Padmei enamoured

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    Yep I learnt real quick not to give my bike its head when it took off going down the Maungatapu. With no engine braking they have to be kept under control at all times. Luckily there was a runoff adjacent to the corner I was missing:D
    #16
  17. Stagehand

    Stagehand Imperfectionist

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    In gear and rear brake applied and you were still drifting backwards? wow. Steep hill <-- :D
    #17
  18. supershaft

    supershaft because I can

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    The stock shoes should work OK but they are still crap. I couldn't tell you how many completely worn out drums I have seen with BMW shoes in there that still look almost brand new. Both of my own bikes have suffered that fate. I see it all the time. My R69S had worn out drums with BMW pads that still looked almost like new. It ought to work the other way around and the brakes will work better for it too!

    Late model bikes can have the wrong shoes in them. I have seen that at lest a couple of times.
    #18
  19. ignatz72

    ignatz72 call me iggy

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    Wait, my GS is supposed to have a REAR brake? Was that an optional extra?!?

    :D
    #19
  20. fishkens

    fishkens Long timer

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    Should I assume that you're talking about riding off-road? Rear brake always on pavement with just an occasional front brake on pavement sounds like long braking distances to me.


    Yes, please share what you learn. Thanks.



    That sounds a lot like my experience. I can lock up the rear pretty easily on pavement regardless of tire (everything from Sahara 3s to IRC GP 110s to Tourances)

    My 88 GS has the original shoes and I don't know which has worn more: the drum or the shoes (never measured, but the shoes still have plenty of pad on them).

    I played with adjusting the play to allow plenty (2 - 3 cm) of lever movement to avoid stomping on it and locking up the rear. Sine then I've gone back to about 1 cm free play in the lever and being careful with modulation on pavement).

    My experience is that there's very little modulation in the rear brake in the dirt. It locks up nearly instantly when things are loose - I'm not sure that an improvement in the brake can fix that since the tire just breaks loose and locks up, esp. down hill.

    This is why I'm more interested in a lower first gear than a higher fifth gear in my GS trans (although traction is still the limiting factor).

    I'm interested in hearing more.

    Lever free play seems to be the biggest variable to me: more freeplay just makes it more difficult for me to apply pressure to the brake.
    #20