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Thread: dual front disc upgrade

  1. #1
    Phil B bullfrog_28560's Avatar
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    dual front disc upgrade

    Hello all,

    I have a question, my 86 r80 currently has a single front brake, with my wife on the back that single brake is less than desireable, i have seen to factory retrofit kits, 1 with a T basically and 1 with a crossover brake line to the right side from the left side bleed screw. which one is better? i know the cross over tube conversion is cheaper according to the microfiche, i will probably be going with used parts to do this addition, parts are much cheaper here in germany on ebay.de versus at home in the U.S.. please lend me your opinions.
    Phil Bouffard
    SSG U.S. Army
    Kaiserslautern, Germany

  2. #2
    Registered User bmweuro's Avatar
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    Quote Originally Posted by bullfrog_28560 View Post
    Hello all,

    I have a question, my 86 r80 currently has a single front brake, with my wife on the back that single brake is less than desireable, i have seen to factory retrofit kits, 1 with a T basically and 1 with a crossover brake line to the right side from the left side bleed screw. which one is better? i know the cross over tube conversion is cheaper according to the microfiche, i will probably be going with used parts to do this addition, parts are much cheaper here in germany on ebay.de versus at home in the U.S.. please lend me your opinions.
    The caliper and brake rotors are the same as all post 85 Airhead models minus the GS so you should be able to find a caliper and disc and you can run two brake lines down to the calipers from the master cylinder and save some money there.
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    I have never seen a second caliper line connected to the bleed screw of the first one. Seems odd and is probably a nightmare when it comes to bleeding the brakes. I would go for the "splitter" solution - one line from the master to the splitter and then two equal lines to the calipers or the dual lines directly from the master, which requires a special bolt to feed both lines.

  4. #4
    Registered User toooldtocare's Avatar
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    Quote Originally Posted by EMSimon View Post
    I have never seen a second caliper line connected to the bleed screw of the first one. Seems odd and is probably a nightmare when it comes to bleeding the brakes. I would go for the "splitter" solution - one line from the master to the splitter and then two equal lines to the calipers or the dual lines directly from the master, which requires a special bolt to feed both lines.
    Actually, if my memory serves me right, both my R80RT (86) and my R100LT (95) had that arrangement. Max BMW also shows this on their website. That said, I never felt comfortable when I bled my brakes, I always wondered how much dirty fluid was left in the calipers. Mike is right, probably better to go with a split system.
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  5. #5
    Registered User bmweuro's Avatar
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    There is a steel line underneath the fender connecting both calipers and one rubber line on one caliper and a bleed screw on the other caliper. It work very well. If you are trying to piece something together it's cheaper to buy a double banjo bolt at the master cylinder and run two separate lines to the calipers. I did this on my '91 project bike.
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  6. #6
    Fixes Gauges tvrla's Avatar
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    The cleanest solution, and simplest, is one line from the master to the right side caliper. Just a bit above the fender there's a T fitting and a second line attaches there to the left side caliper. But that's a custom configuration - something you'll have to have made yourself.

  7. #7
    Phil B bullfrog_28560's Avatar
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    All of you have great advice, I purchased a set of calipers with crossover brake line for 75 bucks. I wanted to get 2 of the same # for the caliper, looking at the fische there were 3 part numbers for calipers. I also bought 2 rotors here in germany for 30 euro. it is difficult trying to find a matching rotor, mine is solid not slotted, i bought 2 slotted rotors, once i get the parts itll be easy.
    Phil Bouffard
    SSG U.S. Army
    Kaiserslautern, Germany

  8. #8
    Registered User jimbc's Avatar
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    Dual disc conversion

    Hi Phil

    Please post your results after riding with the dual disc set up. I'k like to know what difference you note. My 85 R80 also has the single front disc.

    Thanks, Jim

  9. #9
    Phil B bullfrog_28560's Avatar
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    I will post follow up upon installation hopefully in a couple of weeks, i will test it when I am finished even though it is CC C CC Cold here in Germany. Still rode today though. the initial reason why I want to upgrade is my wife rides with me, not her own bike. that added weight adds a challenge to the crake on the BMW, I have a single rotor on my 2005 suzuki and it is not as difficult to stop with her on the back.
    Last edited by bullfrog_28560; 11-06-2012 at 07:19 PM.
    Phil Bouffard
    SSG U.S. Army
    Kaiserslautern, Germany

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    You will probably want to confirm that your master cylinder is designed to serve dual brake calipers - otherwise you will end up with hyper sensitive power brake effect due to the mismatch of the hydraulic volume (my experience is with conversion of R80/7 from single to dual front brake rotors, as well as Honda 750 conversions).
    JWMcDonald
    2003 R1150RS (current) / 1978 R80/7 (prior)
    1966 R69S (prior) / 1972 R75/5 (prior)
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    I too have a 1978 R100 with the single disk. After riding k75's and a k1100lt as well as an '05 RT I think that I really want to be able to stop,not just think about it. I' really lovemy aurhead but I mat cell itand get a late model airhead to solve my problem. The drum on the rear doesn't help.Thanks Is there a reasonable alternative?

  12. #12
    Registered User jad01's Avatar
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    Quote Originally Posted by bmwrn View Post
    Is there a reasonable alternative?
    I don't know what your definition of reasonable is, but I converted my '78 to dual discs sourcing mostly used parts (IBMWR, Airhead Salvage), save for the new Spiegler brake line, caliper rebuild kit, and EBC pads. I think getting it from single to dual discs set me back ~$600-700. It was worth it to me (and my wife, who appreciates the extra stopping power sitting on the back!). It was a pretty straightforward conversion and works a ton better. You might try a new floating rotor, brake line, and new pads- depending on what you are using now, it may make a significant difference for under $300.
    Last edited by jad01; 11-30-2012 at 05:03 AM.
    Jim
    '78 R80/7 and '84 R100RS (Blues Brothers), '86 K75C (Icy Hot)
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  13. #13
    Phil B bullfrog_28560's Avatar
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    I just got my new brake pads in, now i can proceed with my conversion. unfortunately, it is like below freezing and will not be getting above freezing for a few days here in germany. I have taken it off the road for the winter but will test drive it for the dual front brake conversion. So far as the costs are concerned, I payed 95.00 dollars for a set of used matching brake calipers with cross over line. 35,00 Euro for a pair of used rotors, 65,00 euros for 2 pairs of new pads, and 18 euros for a pair pair of caliper bolts, 4 bolts for the rotors. I will update when complete if not tomorrow, next weekend most likely.
    Phil Bouffard
    SSG U.S. Army
    Kaiserslautern, Germany

  14. #14
    Phil B bullfrog_28560's Avatar
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    Job complete

    here is the completed update, all went well sorta, but the brakes are not touchy as some said they have experienced doing a dual disc upgrade. about half pull the brakes really start to grab as before but stops muuuuch quicker. I am satisfied with the original master cylinder. but here is a nice little tidbit. i apparently put 1 pad in backwards, metal to rotor..oops, i went for a short ride, noisy as hell, came back found it switched and all is better. the sun came out enought to melt the snow on the road for the road test. still freezing here though with more snow shortly.

    I also have a question for anyone out there that has the steel line under the fender, is it correct in the picture? i would think the bends would be sorta hidden. i tried installing them so the bend goes towards the center, was not gonna happen.
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    Phil Bouffard
    SSG U.S. Army
    Kaiserslautern, Germany

  15. #15
    Registered User Anyname's Avatar
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    My 86 R80 has factory dual disks with the brake line that runs from the left to the right caliper. The pipe goes back from the fittings and crosses the tire just in front of the fork brace. The front fender mount screws retain small clips that hold the pipe in place.
    BMW R bike rider, horizontally opposed to everything...

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