Advertise on Bikeforums.net



User Tag List

Results 1 to 9 of 9
  1. #1
    Junior Member
    Join Date
    Sep 2013
    Posts
    18
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)

    Square BB length

    I was just wondering if anyone has build a Di2 tandem, 11-36 cassette using JIS square tapered bottom brackets. Rear spacing is 145mm & I'll be using the Gates centertrack timing belt. I'll also be using a double crank set, not a triple converted to a double. BB shell is 68mm. If you have done this & happen to remember the lengths of the bottom brackets that have worked well for you, it would be very helpful.
    Best regards

  2. #2
    Junior Member
    Join Date
    Jan 2014
    Posts
    23
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Can't comment on the BB lengths yet (the bike goes in this weekend to evaluate BB lengths and chainlines for the purchase of a new crankset), but I would recommend getting an extended clamp (unless you braze-on, which may make things more difficult) like the one from K-Edge (assuming that's where you are having the RD modified). I think this moves the FD about 2.5mm outward. With the belt drive, I'm pretty sure the front and rear BB lengths must match (a chain drive gives you a little wiggle room on this).

    Enjoy that DI2... No more frequent cable adjustments, and once you get the system dialed in for your bike shifts are spot-on every time (and as a stoker on a good day I can hear the motors just before the shifts so we don't need to communicate them).

    More on BBs when I get the info.

  3. #3
    Senior Member waynesulak's Avatar
    Join Date
    Jan 2008
    Location
    Ft Worth, TX
    My Bikes
    650B tandem converted from Santana Arriva, Santana Noventa, Boulder Bicycle 700C, Gunnar Sport, Trek TX700,
    Posts
    1,666
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Belt alignment looks like a great reason to use Phil Wood BBs in the appropriate length. A small fine tuning adjustment to "belt line" can be made without using washers or BB spacers.

  4. #4
    coprolite fietsbob's Avatar
    Join Date
    Jun 2010
    Location
    NW,Oregon Coast
    My Bikes
    7
    Posts
    38,939
    Mentioned
    20 Post(s)
    Tagged
    0 Thread(s)
    true, I've pulled a Phil BB axle thru the bearings myself ,, the spline-ring installation tools shoulder against the bearing
    and the crank-arm fixing bolt, thru a big washer over the end pulls it through the sleeve created ..

  5. #5
    Senior Member waynesulak's Avatar
    Join Date
    Jan 2008
    Location
    Ft Worth, TX
    My Bikes
    650B tandem converted from Santana Arriva, Santana Noventa, Boulder Bicycle 700C, Gunnar Sport, Trek TX700,
    Posts
    1,666
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by fietsbob View Post
    true, I've pulled a Phil BB axle thru the bearings myself ,, the spline-ring installation tools shoulder against the bearing
    and the crank-arm fixing bolt, thru a big washer over the end pulls it through the sleeve created ..
    I meant that the design allows for adjusting alignment by loosing one cup in the BB and then tightening the other cup. The cup presses against the BB shell and will move the entire cartridge without moving the bearings on the axle. The result is an asymmetric BB but good for a few mm of adjustment.

  6. #6
    coprolite fietsbob's Avatar
    Join Date
    Jun 2010
    Location
    NW,Oregon Coast
    My Bikes
    7
    Posts
    38,939
    Mentioned
    20 Post(s)
    Tagged
    0 Thread(s)
    Yea , that too ..

  7. #7
    Senior Member
    Join Date
    Mar 2010
    Location
    City of Brotherly Love
    My Bikes
    Raleigh Companion, Nashbar Touring, Novara DiVano, Trek FX 7.1, Giant Upland
    Posts
    1,060
    Mentioned
    1 Post(s)
    Tagged
    0 Thread(s)
    In theory you'd want to move your crankset 7.5mm outwards (assuming that your FD can reach that far) so if you're dealing with a symmetrical BB you'd want a spindle 15mm longer than recommended for a half bike.

    If your timing crank allows you to mount the chainring (or is that beltring?) on either side of the spider you can get away with a narrower captain's BB.

    What crankset are you using?

  8. #8
    Junior Member
    Join Date
    Sep 2013
    Posts
    18
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    I'll be using Da Vinci design billet cranks
    They recommend: 103 -107 spindle length for captain & 107 - 113 spindle length for stokers crank

  9. #9
    Senior Member
    Join Date
    Jul 2005
    Posts
    1,407
    Mentioned
    5 Post(s)
    Tagged
    0 Thread(s)
    As I read it, the o.p. is using a conventional system for the main drive. Only the timing between capt. and stoker is belt drive. IMO nothing fancy need be done to the FD beyond what would work for any other road setup. I think also that the o.p. is in the best situation to determine what chainline is going to work. Or their LBS. I'd start with the spindle length recommended by the crank manufacturer and work shorter from there if need be.

    H

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •