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  1. #1
    Senior Member trayraynor's Avatar
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    Setting up a Vintage Mountain Tandem with Disc Brakes

    I would like to add disc brakes to my mountain tandem; we ride 95% on road, and the occasional off-road use will be gravel trails and roads. Here's my current setup:

    1992 Ellison (Aluminum Bicycle Co.) Mountain Tandem
    135mm rear and 100mm front dropout spacing
    Includes disc mounting tabs front (see photo) and rear
    Shimano Deore cantilever brakes
    26-inch mountain wheels
    7-speed Shimano cassette w/ Shimano DX derailleur
    Shimano Deore Triple chain ring
    Riding weight 350# (includes bike)

    I would like to purchase a disc compatible 26-inch wheel set, disc brakes, and disc compatible brake levers. I'm having difficulty sourcing a wheel set with the 135mm rear disc hub. Do you have any suggestions on the setup and sources for the parts?

    P1040575.jpgP1040560.jpg
    Last edited by trayraynor; 06-08-14 at 05:24 PM.

  2. #2
    Senior Member colotandem's Avatar
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    135mm rear disc hubs are common for regular mountain bikes. You should be able to find lots of options.

  3. #3
    Senior Member WNY tandem's Avatar
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    How do you plan on attaching the rear disc caliper to the frame?
    G.R.E.A.T.S.
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  4. #4
    Senior Member trayraynor's Avatar
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    The rear dropout has three threaded holes for mounting a disc brake adapter. I also have the adapter.

  5. #5
    Senior Member chriskmurray's Avatar
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    There are almost always XT/Rhyno Lite wheelsets on closeout at the big online retailers if you are trying to do it cheap. Just have a good builder check them over to make sure they are properly tensioned and stress relieved. This is a very strong set up even though you will not find one with anything more than 36 spokes.

    If you want to go nicer you can look around at custom options.

  6. #6
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    Use as large of rotors as your adaptors will allow just for heat dissipation. We run 203mm on front and back on both our mtn tandems.

  7. #7
    Senior Member trayraynor's Avatar
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    Here are photos of the disc brake braze ons.P1040576.jpg20140609_064052.jpg

  8. #8
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    That looks more like rack mounts on the rear dropout than a disc mount. You mentioned an adapter?

  9. #9
    Senior Member trayraynor's Avatar
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    Rear Dropout Disc Brake Adapter.jpgRear Dropout.jpg

    Here's a photo of the rear dropout disc brake adapter that was originally installed by the builder in 1992. The spacing for the mounting to the dropout is 35mm; the hole spacing to mount the disc brake is 30mm.
    Last edited by trayraynor; 06-10-14 at 07:40 AM.

  10. #10
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    Unfortunately for you, the industry has standardized a bit on disc brake mounting since 1992. The ISO standard is 51mm from hole to hole.

  11. #11
    Senior Member trayraynor's Avatar
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    Quote Originally Posted by mstyer View Post
    Unfortunately for you, the industry has standardized a bit on disc brake mounting since 1992. The ISO standard is 51mm from hole to hole.
    Are you aware of any Disc Brake Adapters that enable a connection between a non-ISO braze-on to an ISO compatible brake caliper?

  12. #12
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    I'd say that your best bet is to contact a local framebuilder and ask how much it would cost to add the needed disc adapter. There are several frame builders in the San Diego area, but not all do TIG welding, the construction method on your frame. I'd start with a call to Holland Cycles.

    STEEL ISO DISK BRAKE MOUNT :: SMALL PARTS :: BRAZON/SMALL PARTS :: Nova Cycles Supply Inc.

  13. #13
    Senior Member trayraynor's Avatar
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    I mocked up the disc brake mount using Avid BB7 mounting brackets, as well as the original mounting adapter, and borrowing the front wheel off my road tandem.

    Take a look, and consider these questions:

    1. Would you attempt to reuse the original adapter? {From what I see I would need to drill and tap a new mounting hole to achieve ISO compatibility, and straighten the bracket, as it is slightly (is that possible with Aluminum?)**
    2. What is the spacing required between the Avid mounting bracket and the disc? Does 3mm seem about right?
    3. Is the Avid bracket arranged at a correct angle?
    20140614_141902.jpg20140614_141735.jpg20140614_141817.jpg20140614_141749.jpg

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  15. #15
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    Quote Originally Posted by trayraynor View Post
    I mocked up the disc brake mount using Avid BB7 mounting brackets, as well as the original mounting adapter, and borrowing the front wheel off my road tandem. Take a look, and consider these questions:
    1. Would you attempt to reuse the original adapter? {From what I see I would need to drill and tap a new mounting hole to achieve ISO compatibility, and straighten the bracket, as it is slightly (is that possible with Aluminum?)**
    2. What is the spacing required between the Avid mounting bracket and the disc? Does 3mm seem about right?
    3. Is the Avid bracket arranged at a correct angle?
    Tray; I would recommend going with early recommendation to find a frame builder to weld on a modern mounting piece directly to the frame. The rig up shown in the pix has a lot of potential for flexing and breakage. Likewise the original mount to the dropout puts all the stress sideways on three boltsm which the modern mounts have stopped doing or reduced or done better. Am glad 1992 has passed so to speak. Hope that helps.

    /k

  16. #16
    Senior Member trayraynor's Avatar
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    Quote Originally Posted by ksisler View Post
    Tray; I would recommend going with early recommendation to find a frame builder to weld on a modern mounting piece directly to the frame. The rig up shown in the pix has a lot of potential for flexing and breakage. Likewise the original mount to the dropout puts all the stress sideways on three boltsm which the modern mounts have stopped doing or reduced or done better. Am glad 1992 has passed so to speak. Hope that helps.

    /k
    Thanks for the input, and for the diagram showing the mounting of the caliper. I'll check with two of the local builders to see if they would be willing to weld a ISO compatible tab onto my aluminum frame... bummer that I had the frame power coated a few years back.

  17. #17
    Senior Member trayraynor's Avatar
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    After some research, here's what I've learned about upgrading to a rear disc brake: A local frame builder, who specializes in aluminum, can add a disc brake mount to the rear triangle. The frame will need to be heat treated. Total cost for the mod is: $270. A new rear wheel with 135mm hub spacing will be ~$225. The Avid BB7 disc kit ~$125. Grand total $620. The heat treatment will ruin the powder coating; I can apply some elbow grease and voila, I'll have a nude aluminum finish.

    I'm in two minds about this upgrade... I want to improve the braking, but such a costly upgrade for such an old bike seems like a potential waste. I haven't yet tried replacing the brake pads with Swiss Kool Stops; but that may be my best bet.

    I would appreciate your input.

  18. #18
    Nigel nfmisso's Avatar
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    Koolstop.
    Nigel
    Mechanical Design Engineer

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