Airhead Brake Upgrade

Discussion in 'Airheads' started by dukestodd, Nov 5, 2008.

  1. dukestodd

    dukestodd Adventurer

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    The following is a request for opinions from people who are smarter about Airheads than I am.

    <?xml:namespace prefix = o ns = "urn:schemas-microsoft-com:eek:ffice:eek:ffice" /><o:p></o:p>
    I have a relatively stock 78' BMW R100/7 with a dual front disk, ATE style brakes and an under tank master cylinder. I also have a set of 84' R100RT dual disk Brembo style forks and a set of Lester mag wheels that I plan to swap in this winter. At the same time I am swapping forks and wheels I would like to upgrade to a handle bar mounted master cylinder.

    <o:p></o:p>
    I know I need to purchase the following parts:<o:p></o:p>
    1. Dual front disks<o:p></o:p>
    2. Front brake calipers<o:p></o:p>
    3. Front brake pads<o:p></o:p>
    4. Braided steel front brake lines<o:p></o:p>
    5. Handle bar mounted master cylinder
    <o:p></o:p>
    <o:p></o:p>
    What I need advise about is:<o:p></o:p>
    1. Is my list complete?<o:p></o:p>
    2. Can anyone recommend part numbers, manufacturers, and appropriate combinations?<o:p></o:p>
    3. Can anyone suggest suppliers of the necessary parts?

    <o:p></o:p>
    I sincerely appreciate any assistance or guidance you are able to provide.
    #1
  2. CurlyMike

    CurlyMike Formerly SaddleSoar

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    wirewrkr is your man. need some throttle items as well...
    #2
  3. crazydrummerdude

    crazydrummerdude Wacky Bongo Boy

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    Just switch to drums, and let 'em whine.

    :lol3
    #3
  4. Wirespokes

    Wirespokes Beemerholics Anonymous

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    Well set-up Ate brakes can work as well as the Brembos.

    All you need is one more disc to match what you've already got.

    For the bar mount master cylinder, you'll need an early R65 or the later (86 -> on) perch (but not from the GS or R100R which are different) to keep the two throttle cables. 81-4 bikes used a splitter that ran one cable from the grip, to a splitter under the tank to each carb.

    Get a 14mm master cylinder - it gives better feel than the 15 and larger that earlier twin disc models came with.

    A good place to get new Brembo calipers is straight from the distributor - I believe some place in Colorado. I don't have a link to them at this time. They were something like $80 a few years ago. And then there are used ones for much cheaper. You're usually pretty safe with used ones.
    #4
  5. Hawk Medicine

    Hawk Medicine Coyote's Brother

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    I guess that Spokes beat me to it and covered the whole subject as well as anyone could.

    But...

    You'll have to find someone other than me to look up parts numbers for ya.

    Thats too much work and it's your bike!
    #5
  6. pommie john

    pommie john Long timer

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    Wirespokes has got pretty well covered.

    Just one thing.
    Brembo callipers come with at least two different mounting hole spacings.
    Measure the distance between the mounting lugs on your forks before you order new callipers.
    #6
  7. mark1305

    mark1305 Old Enough To Know Better Supporter

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    For suppliers , I like to get Brembo specific stuff from Fred Renz at yoyodyneti.com, and all the ancillary parts like pads and hoses and rotors from cyclebrakes.com
    #7
  8. dukestodd

    dukestodd Adventurer

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    Thank you to everyone - I really appreciate your assistance.
    #8
  9. eepeqez

    eepeqez Long timer

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    Ressurecting an old thread covering the same ground here;

    I've got a 1984 (late twin shock) R65 with the original factory fitted single Brembo disk and 12mm master cylinder, which is weeping, as they do...

    The m/cyl was stainless sleeved many years ago so I expect it needs a hone and seals. I haven't found a source of seals without the piston.

    I've also got a second disk, opposite side caliper and 15mm master cylinder with no piston. This master cylinder would want sleeving and a piston and seals.


    I had assumed that to fit the second disk I would have to go to the 15mm master cylinder, but from this thread and others I see people using smaller master cylinders. I actually had no idea there were more than 2 sizes to fit my throttle/switchgear etc.


    A smaller master cylinder bore should provide higher line pressure for a given lever force, but displaces less fluid, so the lever needs to be pulled in further. Obviously the lever cannot be allowed to get to the bar!

    Any opinions, experience? I can't see the 12mm cylinder being satisfactory but I could get it bored out to 13mm or 14mm if pistons are available and this is a better answer.

    Graham in Melbourne
    #9
  10. dilandau

    dilandau Been here awhile

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    hey, i put a radial master on my r100 - dual disk. they come in various piston sizes and you wont have to worry about hitting the bar, as you can adjust them out to fit. (they adjust radially - in and out from the bar to fit your reach and wanted pull)

    its not very period correct - but it was a vast improvement over the stock if you want to go that way.
    #10
  11. Grafspee

    Grafspee one bike is never enough

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    Pictures??? Would love to see that set up!
    #11
  12. dilandau

    dilandau Been here awhile

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    currently its functionally good, but still not aesthetically squared away. i wanted to make it work before i worried about being pretty.

    straight forward though-- i just tore out the under the tank master-- and stuck on the radial master with some stainless lines to my oh so awesome ATE calipers. i did a fake rebuild of those as well, just took apart, replaced seals and home honed the cylinders with a soft sanding wheel. the disks are semi-floating from "braking USA" and i used the stock brake hubs ( had to cut the rivets off). new pads, and some alignment and wow!

    i have brakes!!!!!!! nearly as good as a honda. but actually, yeah, two fingers no problem. its a heavy bike, but the brakes will dive the front end right to the ground. [​IMG]

    [​IMG]

    i just ground off the old lever mount so i could fit it. i need to take it back off and grind more and then paint to make it look nice. and get a little something better than zip ties to hold up the reservoir.

    if someone wants to do it- i just called up spiegler and they built the lines to fit, and of course 10x1 banjo bolts all around and a double banjo for the master. the master comes with a bleeder valve on the top, which made bleeding very doable. i also put in the braided lines for the rear just for kicks, but i cant tell any difference there. i just used a string to estimate the length of the lines and it worked out alright. a little long on the far one.. but if i tuck it up inside it looks ok.

    i suspect the semi-floating is making a big difference, as the Achilles heal of the ate caliper is alignment, and having disks that can adjust a little to fit snug is making a big difference ( I suspect)
    #12
  13. pommie john

    pommie john Long timer

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    Brembo master cylinders come in three sizes of piston. 12, 14 and 15mm.

    The 12 is designed for a single disc, and the 14 and 15mm for twin discs. Obviously the 15mm gives a more solid feel and the 14mm a softer feel but more stopping power for a given lever pressure.
    #13
  14. eepeqez

    eepeqez Long timer

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    Thanks for this. Sounds like ideally I'd choose the 14mm, but since I've already got a 15mm, thats the way to go. Unless of course I can get it sleeved down to 14mm when it is stainless steel sleeved.... hmmm
    #14
  15. jtwind

    jtwind Wisconsin Airhead

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    Personally I like to leave airheads as stock as possible. Your bike with dual ATE's will stop just fine if you rebuild the mc, rebuild the calipers, and install a ss line and new shoes. Up to brembos? not sure but close and for less money and it's till original.
    #15
  16. dilandau

    dilandau Been here awhile

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    stopping just fine is relative-- i ride that beast in San Francisco city/freeway taffic and it needs to stop better than just fine. it needs to stop very very fine.

    You loose quite a bit by going from "lever to cable to lever to piston" before piston to line engage. going to the bar lever does "lever to piston". mechanically its no contest as far as efficiency of applied force. going with a stock bar/master from a different bmw would have been more correct, but the radial one has the advantage of adjustable pull so i can get it right where it feels nice, and not have to just go with how it works out.

    i like original too, but you got to balance that with how you are planning to use the bike.
    #16
  17. Hawk Medicine

    Hawk Medicine Coyote's Brother

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    Ok...

    On the R-90HR I rebuilt the entire front end, including the brakes. Then I looked through my disk collection and cleaned up the best pair I had and added SS lines.

    The first master cyl I tried was a 14MM Under-tank unit, swiped from an RS.

    The double disk system was a night and day improvement over the single disk but four weeks and 500 miles later, I picked up a 14mm bar mounted system in 100% good shape and plumbed it in through an under-tank splitter.

    Now I have good brakes! I also own an 82RS with Brembos and the Brembo's are still better/smoother brakes but the R-90 is just fine as it is and I think that that's because the RS his a heavier bike because of thefairing and just feels different.

    Next thing, I'll be looking at the possibility of swapping different calipers onto the later Brembo style forks. That should make a difference!
    #17
  18. jtwind

    jtwind Wisconsin Airhead

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    Sounds like fun. If it were me I'd move, failing that I'd buy a modern, nimble, expendable commuter rather than trying to build one out of something I had. But that's me and being practical is something I've just started to try out.
    #18
  19. Bigger Al

    Bigger Al Still a stupid tire guy Supporter

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    Being practical is over rated.:deal
    #19
  20. Wirespokes

    Wirespokes Beemerholics Anonymous

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    My 77S (with RS fairing) is one of the best stopping airheads I've got, except for the R100R with four-piston calipers. And I'm not sure why that is, it just came to me that way - stainless lines, bar mount master, old worn discs, and I don't know what pads it's got - but one of these days I'll pull them apart just to find out. I sort of recall pulling the calipers apart and cleaning everything up really well and replacing the fluid. Those last two things can make a big difference.

    And there is a 13mm bar mount master available, and it may work with a dual disc system, but not sure. The 'RS' has a 15mm and I'll be changing it out for a 14mm before too long because the lever doesn't have much travel. Two fingers gets the front end diving pretty well though, and hauls it right down from speed. A 14 would give better feel and more control, besides more leverage, so the brakes should be even better.
    #20