Advertise on Bikeforums.net



User Tag List

Results 1 to 10 of 10
  1. #1
    Has coddling tendencies. KiddSisko's Avatar
    Join Date
    Jul 2005
    Location
    Topanga Canyon
    My Bikes
    2008 Blue RC8 w/ '09 Rival
    Posts
    8,015
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)

    JB Weld crank bearing fix

    Warning: A story about a guy with time and mad skills saves a few $100.

    I just extended the life of my SRAM Rival crank with the use of JB Weld. I recently purchased a new set of pedals (Look click-it) and shoes (Shimano). With all new pedals, shoes and cleats, I began noticing a hitch in the left crank whenever pedaling hard uphill. Some sort of give. Re-tightening the crank arm did nothing. I also began noticing the tell-tale sound of bearings (ceramic, mid-range price) on their way out.

    So in anticipation of a big day Saturday (riding up to the finish of ToC stage 7 in advance of the pros), I decided to replace the worn bearings with the never been used stock bearings that came with the BB. Before re-tightening things up, I tested the fit of the new bearings. I was surprised there was so much give between the left side inner bearing race and the crank axle. It was not a tight fit at all, and partly explained the hitch I felt while pedaling. A high stress point, once wear begins along that metal surface (the crank axle support race), it just worsens with repeated use.

    Ordinarily, this would mean a new crank is in order. But wait, perhaps I could extend it's life by tightening up that surface area by applying a layer of JB Weld? You know the stuff - 2 part epoxy that can do/repair anything/everything. I've worked with it extensively over the years, so I knew it was possible. The trick in this instance was ensuring that A.) it cured in time and B.) I didn't permanently weld the bearing to the crank axle.

    The proceedure was: apply a thin layer along the axle mating surface, let it begin to cure with the aid of a heat ***, then slide the bearing over the axle to it's resting spot, quickly remove the bearing and clean off the squeezed out excess epoxy. After some additional heat assisted curing, slide a water moistened bearing (the inner race surface) over the axle one more time, and remove.

    Before it fully hardens is the time to reassemble the BB and crank, this time using a thin layer of grease as the lubricant between the axle and bearing surface. The result? A rock solid fit. I'll know more once the climbing begins, but experience tells me it'll work fine.
    "We understand what you are saying. I don't think you understand what you are saying." - umd

  2. #2
    Senior Member miamijim's Avatar
    Join Date
    Aug 2003
    Location
    Tampa, Florida
    Posts
    11,811
    Mentioned
    17 Post(s)
    Tagged
    1 Thread(s)
    Maybe it'll work, maybe it wont.

    I've used Loctite to fix loose hub races with very good success.
    WWW.CYCLESPEUGEOT.COM 2005 Pinarello Dogma; 1991 Paramount PDG 70 Mtb; 1976? AD Vent Noir; 1989 LeMond Maillot Juane F&F; 1993? Basso GAP F&F; 1989 Terry Symmetry; 2003 Trek 4700 Mtb; 1983 Vitus 979

  3. #3
    has a Large Member Campag4life's Avatar
    Join Date
    May 2007
    Posts
    8,412
    Mentioned
    8 Post(s)
    Tagged
    0 Thread(s)
    While I applaud your creativity and have used JB Weld extensively and concede it is great stuff, I would not use it for this application.
    It really isn't clear what you did by your description though or even what the role of JB Weld is here...increase bearing pre-load?...JB Weld in pure compression without shear forces? etc. It maybe OK 'short term' but if the crank shoulder wore increasing axial play with the bearing race...perhaps insufficient heat treat on the crank, JB Weld will decay rapidly as it doesn't have near the structural integrity as the crank axle...much lower yield strength and abrasion resistance.
    Again I wouldn't do it but if it works for you then good...the question will be how long of course.
    Last edited by Campag4life; 05-21-11 at 06:10 AM.

  4. #4
    Underwhelming MrTuner1970's Avatar
    Join Date
    Nov 2009
    Location
    Northeast Mississippi
    My Bikes
    Lynskey R330 Ti, Dean El Vado Ti, Trek 4300
    Posts
    1,263
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    I wouldn't be too hopeful.

  5. #5
    Senior Member mvnsnd's Avatar
    Join Date
    Aug 2010
    Location
    WNY
    My Bikes
    old bikes
    Posts
    1,941
    Mentioned
    3 Post(s)
    Tagged
    1 Thread(s)
    You have that new axle and bearing kit on order. right?

    I do think you approached the repair in a good way, but I don't think it will last very long at all.

  6. #6
    Has coddling tendencies. KiddSisko's Avatar
    Join Date
    Jul 2005
    Location
    Topanga Canyon
    My Bikes
    2008 Blue RC8 w/ '09 Rival
    Posts
    8,015
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Such negative Nancys! For my test run, I climbed to the top of today's Tour of California stage on Mt Baldy. It totally worked and took out that nagging play between the left side mating surface of the crank axle and BB bearing inner ring. Here's a picture to illustrate. This is just before re-assembly, after the final trim and pre-sliding of the bearing. Look how much JB Weld remained after sliding the new bearing over it. Without that thin layer, the axle floated back and forth a tiny bit when pedaling hard. Felt like a hitch and sounded like a pop.

    "We understand what you are saying. I don't think you understand what you are saying." - umd

  7. #7
    Senior Member Homebrew01's Avatar
    Join Date
    Jul 2004
    Location
    Ffld Cnty Connecticut
    My Bikes
    Old Steelies I made, Old Cannondales
    Posts
    15,453
    Mentioned
    6 Post(s)
    Tagged
    1 Thread(s)
    Welcome to the "Break the Rules" Club.

    I've done several repairs & fixes that aren't supposed to work, but they do.
    Bikes: Old steel race bikes, old Cannondale race bikes, less old Cannondale race bike, crappy old mtn bike

  8. #8
    Has coddling tendencies. KiddSisko's Avatar
    Join Date
    Jul 2005
    Location
    Topanga Canyon
    My Bikes
    2008 Blue RC8 w/ '09 Rival
    Posts
    8,015
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Here's the before shot. Looks fine, but it was quite worn from thousands of miles with lots of climbing. Hey, things wear. I just extended it's life.

    "We understand what you are saying. I don't think you understand what you are saying." - umd

  9. #9
    Senior Member ericm979's Avatar
    Join Date
    May 2007
    Location
    Santa Cruz Mountains
    Posts
    6,170
    Mentioned
    1 Post(s)
    Tagged
    0 Thread(s)
    Loctite 641 is made for that sort of thing.

  10. #10
    Has coddling tendencies. KiddSisko's Avatar
    Join Date
    Jul 2005
    Location
    Topanga Canyon
    My Bikes
    2008 Blue RC8 w/ '09 Rival
    Posts
    8,015
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Eric, does Loctite cure in a manner so you can work with it like with JB? The goal isn't to bond the bearing to the axle, especially that left side bearing, otherwise you can't remove the crank. The JB was used in this instance to fill the gap that caused the excess play.
    "We understand what you are saying. I don't think you understand what you are saying." - umd

Posting Permissions

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