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Thread: Brake System Overhaul Yes or No

  1. #1
    Registered User 88bmwjeff's Avatar
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    Brake System Overhaul Yes or No

    So, my plan was to restore my 1988 R100 RT after purchasing my GS. However, I spent a bit too much on my GS and now I have to put off the restoration. The bike really should have some repairs to make it more reliable so I can ride it until I can get to the restoration. I have some questions regarding the brake system.

    The bike is ±35 years old. What are people’s thoughts regarding rebuilding the calipers and/or master cylinder? My thought is to disassemble and replace all the O-rings and gaskets at a minimum, and anything else that may seem out of spec. After ±35 years, I would think the O rings and perhaps the gaskets at the end or nearing the end of their economic/useful lives. However, I’m unaware of any major issues—the brakes seem to work OK at the moment. Should I be proactive here and rebuild them, or wait and repair as needed down the road? FYI, I do plan on replacing the brake lines with braided stainless lines.
    Jeff
    1988 R100 RT (the other woman)
    2018 R1200 GS
    "I got my motorcycle jacket but I'm walking all the time." Joe Strummer

  2. #2
    Registered User STEVENRANKIN's Avatar
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    Is it that old and been sitting or have you been riding it regularly? Has the brake fluid been changed at all in it's life? If you say yes, to both questions I would suggest riding until you have a problem or need to replace pads in the calipers.

    When you do pull the system apart, stainless brake lines are a good upgrade. St.

  3. #3
    Dances With Sheep GREGFEELER's Avatar
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    Quote Originally Posted by STEVENRANKIN View Post
    Is it that old and been sitting or have you been riding it regularly? Has the brake fluid been changed at all in it's life? If you say yes, to both questions I would suggest riding until you have a problem or need to replace pads in the calipers.

    When you do pull the system apart, stainless brake lines are a good upgrade. St.
    I agree. I've never had a caliper failure from age or contaminated lines. I'm not saying that can't happen, or that you shouldn't rebuild old systems - just that they seem to be built with quality materials and can last a very long time in service, and when calipers do need service all I've heard if is slow leaks around the piston - not catastrophic failures.
    Greg Feeler
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    1972 R75/5, 1990 K75, 1990 K1, 1992 K75S, 2003 K1200RS

  4. #4
    Registered User STEVENRANKIN's Avatar
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    The original hoses can break down internally with time, seals do go over time. I have rebuilt my handlebar MC twice in 230K miles. the original hoses were replaced at the first rebuild with ss ones.

    The key too long brake system life is keeping the fluid changed. The handlebar systems seem unscientifically to have fluid break down faster than the old under the tank systems. I am guessing it is due perhaps to sunlight, and the chance of rain water from a more exposed spot contributes. LOL, at least with the handlebar unit, it is quicker to spot a leak than the under the tank units.

    Moisture is the big bug, it is the cause of pitting, but that rarely happens in a well maintained system. For sure it happens a lot on a bike sitting in storage. St.

  5. #5
    Registered User 6322's Avatar
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    Hoses and brake fluid regardless. Stainless hoses and fresh fluid will give you a good baseline.
    Gary Phillips - #6322
    Wildland Firefighter, Retired, Riggins, ID
    Heartland Moto Locos BMW Riders
    '77 R100/7 Dirt Hack, '83 R80ST, '85 K100RS w/EML, '93 K1100LT, '00 R1100RS

  6. #6
    Are these a possibility on your model ? I was pleasantly shocked at the price compared to most bikes
    by the time I could throw all the necessities into the brembo on back of my 78, felt good to find a NIB/loaded caliper for a very few beans more ...

    I'd pop the caliper apart and check the bore / puck condition, & have seal kits on hand in case everything is good to go.

    Both ATE up front on my 78 ( mostly dry / desert life) were clean
    while the brembo on back had scrap pucks and iffy bore quality.

    My aluminum rear master cleaned up with a ball hone ( no miles yet so YMMV mine too! )
    while the iron master hit 1 deeper pit on bore wall, opposite the inlet port. ( I suspect cavitation pitting without proof)
    I had it relined with a brass sleeve by Appleton Hydraulics and put a RB kit in it

    bmw R100S brembo f08 rear - 1 (1).jpeg

  7. #7
    I would completely overhaul the system and include any upgrades to increase performance. When you do the calipers use red rubber grease to install the pistons.
    '13 690 Duke, '19 Ninja 400 (track bike), '21 Duke 890R, '22 Street Triple RS, '22 S1000XR (gone but not forgotten: '61 Clubman's Gold Star, '76 R75/6, '84 R100, '76 R90S, '20 R1250R)

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