Advertise on Bikeforums.net



User Tag List

Results 1 to 9 of 9
  1. #1
    Senior Member Bolo Grubb's Avatar
    Join Date
    Jun 2004
    Location
    Tucson, AZ
    Posts
    1,749
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)

    rear derailuer adjustment with 2 wheelsets

    ok let me see if I can explain this.

    For 1 bike I have 2 wheel sets. Should I expect to be able to swap the rear wheels with no adjustment to the derailuer?

    Both wheels have a 9 speed cogset. One cog set is a shimano 12-25 the other a SRAM 12-26.


    When I put the shimano cog wheelset on the bike for trainer use, I got some cog skipping in the largest 2 cogs.

    what is causing this? and How can I fix it? Or is this normal when switching wheels.

  2. #2
    Senior Member
    Join Date
    Feb 2005
    Location
    Oklahoma
    My Bikes
    Trek 5500, Colnago C-50
    Posts
    9,209
    Mentioned
    2 Post(s)
    Tagged
    0 Thread(s)
    It depends on what kind of skipping you've got. If it acts like it's trying to shift from one cog to another then you can correct this with a cable adjustment by turning the barrel adjustor. Counter-clockwise moves the derailleur toward the frame, clock-wise moves it out. When you change wheels again you may need to re-adjust the derailleur.
    Or it's possible the the offending cogs are worn out.
    And check your chain for stretch. Replace if a 24 pin length measures as much or more than 12 1/16th inches.

    Al

  3. #3
    biked well well biked's Avatar
    Join Date
    Jul 2005
    Posts
    6,883
    Mentioned
    2 Post(s)
    Tagged
    0 Thread(s)
    Unfortunately, even with the small difference in a 25t and 26t large cog, you'll probably have to do a little tweaking of the B screw on the rear derailleur (the b screw adjusts the angle of the derailluer body, giving the desired small gap between the upper pulley and the large cog) when you switch back and forth between wheelsets. Since the two cassettes are so close to being identical (the SRAM cassette is "Shimano compatible", so that aspect makes no difference), I'd determine which one you like best and buy another one just like it, that way you should have complete compatibility between the two without having to make any adjustments when you swap wheels. I've got two identical wheelsets for a mtb I have, with identical nine-speed casettes on them (I use one for road tires, one for knobbies), and I can switch between the two with no problems-
    Last edited by well biked; 10-04-06 at 02:09 PM.

  4. #4
    Senior Member Bolo Grubb's Avatar
    Join Date
    Jun 2004
    Location
    Tucson, AZ
    Posts
    1,749
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    thanks, it is possible that the shimano cassette is somewhat worn out, but I doubt it. The chain is fairly new.

  5. #5
    Elitist Troglodyte DMF's Avatar
    Join Date
    Jun 2006
    Location
    Dallas
    My Bikes
    03 Raleigh Professional (steel)
    Posts
    6,896
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Or the chainline isn't the same for the two cassettes, in which case you could shim one.
    Stupidity got us into this mess - why can't it get us out?

    - Will Rogers

  6. #6
    Senior Member
    Join Date
    Mar 2006
    Posts
    431
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    I have similar setups with my indoor trainer wheel,
    shimano hg 12-25 and sram 12-25 they both work fine
    so I suspect could be wear since the cog spacings should be the same and not affect the derailleur once the high and low work

  7. #7
    Has opinion, will express
    Join Date
    Jun 2003
    Posts
    13,032
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    It sounds like cogset wear if the chain is new, and the Shimano cassette is more worn than the SRAM one.
    Dream. Dare. Do.

  8. #8
    ot.net slave
    Join Date
    Feb 2006
    Location
    Canberra, Australia
    My Bikes
    Salsa mtb * 3, Intense mtb * 1, Abeni SS rd * 1, Salsa road/touring * 2, Trek Damn one * 1, Vintage/projects * many
    Posts
    554
    Mentioned
    1 Post(s)
    Tagged
    0 Thread(s)
    I've fixed this problem in the past by respacing the axle slightly on the two hubs. Often the freehub to locknut distance will be (slightly) different with different hubs. I just use thin washers to do the respacing. The total change is typically less than 1mm.

    - Joel

  9. #9
    Senior Member
    Join Date
    Dec 2004
    My Bikes
    1982 Bianchi Superleggera (restored with NOS campagnolo components), 1987 Bianchi Campione Del Mundo, 1995 Bianchi Denali (M900/950 XTR components, viscous cycles rigid fork, mavic ceramics), 1996 Specialized Hardrock (winter beater, 8 speed XT group
    Posts
    175
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by tomacropod
    I've fixed this problem in the past by respacing the axle slightly on the two hubs. Often the freehub to locknut distance will be (slightly) different with different hubs. I just use thin washers to do the respacing. The total change is typically less than 1mm.

    - Joel

    +1

    Also, are the hubs identical? If not this may be causing slightly different alingment. Even with identical hubs the exact alingmernt will depend on axle spacing. Shim as described above and/or respace slightly to get equal distance from small cog to outer of driveside locknut.

    Since Sram and Shimano index the same I doubt this is the root of the problem (UNLESS the cogsets sit slightly deeper/higher on the freehub body). If it was then you would have a real problem like you get when mixing shimano/campy cassttees/shifters

Posting Permissions

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