Advertise on Bikeforums.net



User Tag List

Results 1 to 9 of 9
  1. #1
    Philologist
    Join Date
    Jun 2008
    Location
    Birmingham, Alabama
    My Bikes
    Univega Gran Turismo
    Posts
    437
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)

    Crank torque question

    I have an SR Custom triple crankset (square spindle) and I haven't been able to find exact torque specifications for the cranks. Barnett's Manual says "In absence of manufacturer’s recommendations, torque to 350 inch-lbs" and I tried that. But afterward, it wouldn't shift to the smallest chainring any more. It [i]almost/i] shifted, but not quite. Apparently the chainrings are now slightly closer to the frame than they used to be. So I pulled the crank again and re-torqued it to 300 inch-lbs, plus adjusting the lower limit screw on the front derailleur a bit. Now it shifts correctly and the crank seems tight enough.

    Did I do the right thing? Should I have left the crank torqued to 350 inch-lbs and just loosened the FD limit screw more? Also, the non-drive side crank is still torqued at 350 inch-lbs. Should I leave it alone or reduce it to match the drive-side crank?
    Þæs ofereode, ðisses swa mæg. ("That passed away, this also can.")
    from Deor, in the Exeter Book (folios 100r-100v)

  2. #2
    Senior Member
    Join Date
    Aug 2005
    Location
    Pittsburgh, PA
    My Bikes
    '''96 Litespeed Catalyst, '05 Litespeed Firenze, '06 Litespeed Tuscany, '12 Surly Pacer, All are 3x8,9 or 10. It is hilly around here!
    Posts
    25,416
    Mentioned
    5 Post(s)
    Tagged
    0 Thread(s)
    Yes, you should have just tweaked the lower limit screw the first time. Removing and replacing square taper cranks repeatedly isn't a real good idea but can be done without harm if you torque them once per installation.

    I'll bet the reduction from 350 to 300 inch-pounds isn't what solved your problem but the limit screw adjustment did.

  3. #3
    Senior Member
    Join Date
    May 2004
    Location
    Wilmington, DE
    My Bikes
    2003 Specialized Hardrock, 2004 LOOK KG386i, 2005 Iron Horse Warrior Expert, 2009 Pedal Force CX1
    Posts
    8,849
    Mentioned
    1 Post(s)
    Tagged
    0 Thread(s)
    Personal opinion would be to torque to spec and adjust the FD. The FD adjustments are easy; having a crank arm come loose would suck, to put it in simple terms.

    I recently went through this with a square taper crank on my road bike. I had pulled the crank to try and find the source of a creaking noise (never did fix it) and retorqued to the middle of the manufacturers spec, as opposed to the lower end that I was using. I had to adjust my FD to be able to get into the little ring and to keep it from shifting off the big ring.

  4. #4
    Philologist
    Join Date
    Jun 2008
    Location
    Birmingham, Alabama
    My Bikes
    Univega Gran Turismo
    Posts
    437
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by HillRider View Post
    Yes, you should have just tweaked the lower limit screw the first time. Removing and replacing square taper cranks repeatedly isn't a real good idea but can be done without harm if you torque them once per installation.

    I'll bet the reduction from 350 to 300 inch-pounds isn't what solved your problem but the limit screw adjustment did.
    Actually, it was both; I adjusted the FD first and it worked OK while stationary, but on a test-ride it hesitated and didn't shift smoothly. After re-torquing the crank it shifted quickly and smoothly again.
    Þæs ofereode, ðisses swa mæg. ("That passed away, this also can.")
    from Deor, in the Exeter Book (folios 100r-100v)

  5. #5
    Philologist
    Join Date
    Jun 2008
    Location
    Birmingham, Alabama
    My Bikes
    Univega Gran Turismo
    Posts
    437
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by joejack951 View Post
    Personal opinion would be to torque to spec and adjust the FD. The FD adjustments are easy; having a crank arm come loose would suck, to put it in simple terms.

    I recently went through this with a square taper crank on my road bike. I had pulled the crank to try and find the source of a creaking noise (never did fix it) and retorqued to the middle of the manufacturers spec, as opposed to the lower end that I was using. I had to adjust my FD to be able to get into the little ring and to keep it from shifting off the big ring.
    So should I go ahead and torque it a bit more, back up to 350 inch-pounds, and adjust the FD again if necessary?
    Þæs ofereode, ðisses swa mæg. ("That passed away, this also can.")
    from Deor, in the Exeter Book (folios 100r-100v)

  6. #6
    Senior Member DannoXYZ's Avatar
    Join Date
    Jul 2005
    Location
    Saratoga, CA
    Posts
    11,495
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    YES! Definitely do NOT use crankarm-bolt torque as an "adjustment". Use other things that are adjustable to fine-tune the bike, like FD limit-screws and cable-tension. You just have to search "loose crankarm" on here to see how common the problem of loosening crankarms is. A buggered crankarm may not be that big a deal, but certainly is more frustrating than shifting problems, especially if it falls off miles away from home.

  7. #7
    Philologist
    Join Date
    Jun 2008
    Location
    Birmingham, Alabama
    My Bikes
    Univega Gran Turismo
    Posts
    437
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by DannoXYZ View Post
    YES! Definitely do NOT use crankarm-bolt torque as an "adjustment". Use other things that are adjustable to fine-tune the bike, like FD limit-screws and cable-tension. You just have to search "loose crankarm" on here to see how common the problem of loosening crankarms is. A buggered crankarm may not be that big a deal, but certainly is more frustrating than shifting problems, especially if it falls off miles away from home.
    OK, I'll put it back to 350 inch-lbs. That particular value seems rather arbitrary to me, since it wasn't a specific recommendation for my particular cranks, but a generic "if you can't get it elsewhere, use this" value. However, since I've already had it up to 350 once, I can see how it might get loose if I tried to use a lower torque now.
    Þæs ofereode, ðisses swa mæg. ("That passed away, this also can.")
    from Deor, in the Exeter Book (folios 100r-100v)

  8. #8
    slow as I ever was Ex Pres's Avatar
    Join Date
    Dec 2007
    Location
    an imposter living in the 35223
    Posts
    5,652
    Mentioned
    5 Post(s)
    Tagged
    0 Thread(s)
    +1 Danno. You're doing the right thing. Torque it up.

    We have several of us vintage bike & component knuckleheads here in B'ham if you ever want any help.
    72 special CNC ___________ 72 Frejus (ala Legnano) __73 Holdsworth Record
    78 Raleigh Professional_____ 80 Ranson_____________ 80 unknown French (SS)
    82 Peugeot PXN10_________83 Trek 620 (nee 600)____ 85 Gianni Motta
    85 Trek 560______________88 Guerciotti GLX
    90 Miele Gara_____________02 Casati Dardo (g/blue)__02 Casati Dardo (y/blk)
    03 Casati Dardo___________08 BF IRO (fixed)________10 Vassago Fisticuff (IGH)

  9. #9
    Senior Member
    Join Date
    May 2004
    Location
    Wilmington, DE
    My Bikes
    2003 Specialized Hardrock, 2004 LOOK KG386i, 2005 Iron Horse Warrior Expert, 2009 Pedal Force CX1
    Posts
    8,849
    Mentioned
    1 Post(s)
    Tagged
    0 Thread(s)
    FWIW, Shimano recommends approximately the same torque value for it's square taper cranksets. I've used 360 in-lbs (30 ft-lbs) on all of the square taper cranks I've installed without issues.

Posting Permissions

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