Advertise on Bikeforums.net



User Tag List

Results 1 to 6 of 6
  1. #1
    Junior Member
    Join Date
    May 2006
    Location
    Sunset Beach, CA
    My Bikes
    1978 Trek TX700 1986 Trek 560 Pro Flatbar 1995 Performance (Yes, Performance) M405MTB
    Posts
    17
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)

    10 Speed to 18 Speed Conversion Chainline Issue

    I just recently acquired a TREK 560 Pro (1986) 531 frame and updated it to Shimano 9 Speed with SRAM 970 12-26 cassette. While tuning it up for the first ride I noticed that the chain ,when on the small chainwheel (39) and high cassette cog (12) rubs on the inner face of the large chainwheel. Uh oh, chain line problem I changed out the BB from 109.5 to 119 (just happened to have one on hand, thank you ebay). I still have the same result. It only does this in this gear combination so does anyone have a solution or am I SOL and will not just be able to use this gear combo?

  2. #2
    Senior Member capwater's Avatar
    Join Date
    Dec 2004
    Location
    Quahog, RI
    My Bikes
    Giant TCR Comps, Cdale R5000, Klein Q-Pro, Litespeed Siena, Piasano 105, Redline Conquest Pro, Voodoo Bizango, Fuji Aloha
    Posts
    1,509
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    It is a condition called "cross chaining" and unavoidable, same dealio with 53 and 26. Big/big and little/little are no-nos. Go put the 109.5 bottom bracket back on, it's the correct spec for a double.

  3. #3
    Junior Member
    Join Date
    May 2006
    Location
    Sunset Beach, CA
    My Bikes
    1978 Trek TX700 1986 Trek 560 Pro Flatbar 1995 Performance (Yes, Performance) M405MTB
    Posts
    17
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Interesting. I'm the original owner of a 1978 Trek Tx700 as well. I just recently had the rear drop outs spread to 130mm(as I did on the 560) and upgraded the TX700to DA. The BB spindle on this one had always been 118mm. I changed the BB to 109.5mm as per DA specifications. It has worked out perfectly. I now have the original DA 600 crankset (after many hours at the buffing wheel) on the 560 with recent Ultegra chainwheels. It looks great--kinda retro. I have noticed that the chainstays are shorter on the 560 as opposed to the TX700. I'm sure that this has something to do with the crosschaining debacle. Do you still think I should put the Ultegra crank back on with the 109.5er BB, and what solutions are avail such as different drive sys ratios to counter this problem?

  4. #4
    Senior Member thePest's Avatar
    Join Date
    May 2006
    Location
    Pacific NW
    My Bikes
    none at this time
    Posts
    130
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    hello "the snoid

    I kind of have to ask. "Why would you ever ride in your extreme gears???"

    If you did a pull chart you should find that same gear about Large up front and fourth position in the rear.

    By the time you hit the middle sprockets in the small chainwheel you should be going up to the large at this point. Never hitting that combo...

  5. #5
    Junior Member
    Join Date
    May 2006
    Location
    Sunset Beach, CA
    My Bikes
    1978 Trek TX700 1986 Trek 560 Pro Flatbar 1995 Performance (Yes, Performance) M405MTB
    Posts
    17
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    I don't ride in extreme gears, of course, but the fact it does it is annoying, kinda like getting bad reception from that stupid Country Western station that you know you will never, ever listen to but you just want to know why your receptions bad, thats all.

  6. #6
    Cyclin' twosome
    Join Date
    Feb 2006
    Location
    Billings, Montana
    Posts
    53
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    "Cross-gearing" should generally be avoided 'cause it accelerates the wear on the drivetrain components, just as a perfect chainline minimizes wear. Picture the drive-&-driven surfaces of the chainring & cog teeth.... they will wear longer if the force from the chain is applied directly against that surface, as opposed to applied at an angle against the inner or outer edge of the teeth. Likewise, the chain will last longest if driven in a straight line as opposed to an angle. That's why single speed & hub-geared drivetrains generally last longer & often require less maintenance (all else being equal) than derailleur-geared drivetrains. Generally, the middle chainring of a triple can be used with all rear cogs; the inner chainring should be limited to all but the smallest couple of cogs & the outer chainring limited to all but the largest two cogs. Similar on a double chainring setup.
    Hence the references to "useable gears" in postings about derailleur gearing...
    Cross gearing usually produces more noise, too.

Posting Permissions

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