BMW R100GS & R100, bolt on Brembo 4 Piston Caliper Upgrade

Discussion in 'Vendors' started by One Less Harley, Oct 10, 2010.

  1. Reggie Perrin

    Reggie Perrin Airhead Connoisseur

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    Thanks for the further advice, much appreciated.

    After another afternoon bleeding etc, and really getting no further (also tied the brake lever off overnight), I focussed in on your point about the over-sized o-ring. On the basis that the seal is not good, and air is working its way in past the o-ring.

    So, I have completely disassembled the caliper again. Below some photos of the calliper and the o-rings I have.

    When you say "oversized" o-ring, I assume you mean a 10mm but rather thicker? I cannot see how a larger o-ring would work, I have tried inserting the next size up and it just doesn't fit in the recess.

    If you have an e-mail or even telephone number I could give you a call to discuss. It's slightly driving me nuts, as I have been at this on and off for weeks!

    IMG_3318.jpg IMG_3319.jpg IMG_3320.jpg IMG_3320.jpg IMG_3321.jpg IMG_3322.jpg
  2. One Less Harley

    One Less Harley OH.THAT'S GONNA HURT

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    If it were leaking at the o-ring you'd probably set fluid oozing out. I have one recently which was low on pressure but haven't gotten it back yet. I wouldn't use a pressure bleeder as it's not needed. You might try removing the caliper and trying to bleed off the bike and higher than the MC??? MY oversized o-ring is a 2.4x5.3.

    Is you MC up to snuff??

    how about having someone else give it a go on bleeding??
  3. Reggie Perrin

    Reggie Perrin Airhead Connoisseur

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    Thanks for your reply. I have already had my friend try to bleed it...

    Master cylinder is a 13mm BMW, and it is brand new. Same with brake line.

    I haven't tried bleeding it above the MC, it would require me removing the front wheel to get the fixed section of the brake line back in afterwards.

    Thanks for the link on the o-rings, I will measure the thickness of mine tomorrow.

    I get the brake hardness up to a reasonable level, but nowhere near the equivalent on my R100GS with two pots.

    I assume that the feel should be just as hard as the standard two pot?
  4. Reggie Perrin

    Reggie Perrin Airhead Connoisseur

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    Could you please send me the link to where you buy your o-rings, I suspect that they are chunkier than mine.
  5. One Less Harley

    One Less Harley OH.THAT'S GONNA HURT

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    MC master car in the USA, should be a problem finding them over there, but that might not be your problem. IDK...I never did like the stock O-rings since they didn't look like they would compress much.

    upload_2019-11-3_15-56-51.png

    https://www.mcmaster.com/o-rings
  6. One Less Harley

    One Less Harley OH.THAT'S GONNA HURT

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    It's been some time since I had them on my bike, either the two pot or four pot...you should get more lever travel than with the two pot. But if you want to be sure you would have to measure the capacity of each caliper.
  7. Reggie Perrin

    Reggie Perrin Airhead Connoisseur

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    I agree with you on the standard o-ring, it just doesn't look chunky enough to compress and seal something under so much pressure.

    I picked up on your comment that the brake lever travel is more than on the two-pot caliper. At best compression (over many days) I can still easily compress the brake lever to touch the grip. Surely that isn't right?

    I have yet to actually test it on the road, as I did not have much confidence in the braking due to the poor compression.

    In your experience, how much better should be the braking compared to the 2-pot standard caliper? 20%??
  8. One Less Harley

    One Less Harley OH.THAT'S GONNA HURT

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  9. Reggie Perrin

    Reggie Perrin Airhead Connoisseur

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    I just measured the o-ring I have been using, and it is not as substantial as the one you are using:-

    External diameter:- 10.63mm (yours 10.1mm)
    Internal diameter:- 6.22mm (yours 5.3mm)
    Thickness:- 1.76mm (yours 2.4mm)
  10. Cubdriver

    Cubdriver Stampede Swimmer

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    OLH, do you still have a caliper available? Its for an early 1990 R100GSPD. I do have risers on the handle bars. Thanks. Dick
  11. One Less Harley

    One Less Harley OH.THAT'S GONNA HURT

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    I've got one on hand, need to order some pads. Got another three on the way. So a total of four...make that...FIVE

    Plus I'm working on doing a dual caliper four pot for a R100 for a member here.....not sure if it will work yet
  12. One Less Harley

    One Less Harley OH.THAT'S GONNA HURT

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    If you want to get put on the list for calipers I've got 6 on hand......edit, make that THREE....two pictured are for a R100 dual brake conversion, my 1st attempt and I hope it works out!!!!!!

    I can't ship till the EBC Organic pads show up...and talk to me if you want braided stainless lines...they will have to be ordered too...

    This Corona Virus had me knocking these out....so give me a shout....

    6calipers.jpg
  13. Mattcosta7

    Mattcosta7 n00b

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    The dual side conversion set seems to be working great so far!

    [​IMG] [​IMG]

    Calipers fit up great, and braking seems a bit more progressive and more modulatable than the 2 pot stock calipers on the monolever. So far, really happy with the results, thanks!
  14. One Less Harley

    One Less Harley OH.THAT'S GONNA HURT

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    so glad I could help.....between the two of us we figured it out..dual four pots for R100's now SWEET...would you remind me what bike that is.....was..
  15. jimwilling

    jimwilling n00b

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    I'm down for a set for my '88 r100rs if you've still got a set. Pads and a line as well.
  16. Mattcosta7

    Mattcosta7 n00b

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    Oh yeah

    89 r100rt
  17. One Less Harley

    One Less Harley OH.THAT'S GONNA HURT

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    PM me as I'm new to this on other bikes...check your CTC measurement for the calipers you have. The Brembo four pot is 25.42MM.

    108mm is from the center of the rotor to the inner surface of the mounting tab.

    if both these measurements appear correct I can probably help, but it will be a bit as I don't have the caliper for the other side, but can get one relatively quick..
  18. jimwilling

    jimwilling n00b

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    I believe I have the same front forks as the monolever bike Mattcosta7 posted.

    I'm not sure I'm measuring what you're asking for, so to clarify, you need the center-to-center measurement of the caliper-to-fork bolts, and the distance from the rotor wear surface to the inside of the fork's caliper mounting tab?
  19. One Less Harley

    One Less Harley OH.THAT'S GONNA HURT

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    The space between the mounting bolts is 108mm, pretty sure that's what you have. You don't have to measure tot he center but just to the cap sides will give you the same number. These are picts on a R100GS front but it's the numbers that count.

    caliper mnt spacing.jpg

    the other number which is more difficult to measure is from the inner mounting tab to the center of the rotor, that is 25.42mm..near to that.

    roto center.jpg

    caliper centered.jpg