Bicycle TutorBicycle Tutor

Show off your bike!

Related video tutorials:
Stripped out crank arm
#1
I got a bike about a week ago for $15. I was going to use it for parts (for another bike I have), but after examination (and because the rims were the wrong size), I've decided to repair it instead.

Apparently, this specific model crank set has the crank arms separate from the gear assembly. And the left crank arm had stripped out the thread and square peg which it had been fastened to. The entire rest of the bike is in excellent condition, though I'm planning to replace the brake pads.

[attachment=4577]

My idea is to drill a hole through the peg straight into the crank arm, liberally apply J.B. Weld over the whole area, and force a nail into the hole I drilled. If it goes like I plan, it should create a very strong joint.

Has anyone ever encountered a problem like this before?
Reply
#2
This is a common problem. I would recommend just buying a new "bottom bracket" (bearing assembly) and a new crank set or at least a new left crank arm. Or find another parts bike to strip.

Your concept may work for a while, but I'm guessing not that long. This is a very high stress area and you typically have a steel axle with aluminum crank arm. Drilling holes in it will make the whole thing prone to snapping off and possibly injuring you. JB Weld is also basically epoxy. Despite the name, it has nothing to do with "welding" and none of the strength implied by the name. I've seen crazier schemes work, but I wouldn't ride it...
Reply
#3
(10-21-2013, 09:07 PM)DaveM Wrote:  This is a common problem. I would recommend just buying a new "bottom bracket" (bearing assembly) and a new crank set or at least a new left crank arm. Or find another parts bike to strip.

Your concept may work for a while, but I'm guessing not that long. This is a very high stress area and you typically have a steel axle with aluminum crank arm. Drilling holes in it will make the whole thing prone to snapping off and possibly injuring you. JB Weld is also basically epoxy. Despite the name, it has nothing to do with "welding" and none of the strength implied by the name. I've seen crazier schemes work, but I wouldn't ride it...

When I test-fitted the crank arm, it fit very snugly (no looseness at all). I'm not sure why the previous owner thought it was broken.
So, instead of drilling the hole, I simply smeared the entire area with J.B Weld to help prevent any minor slippage that may occur, and then bolted the crank arm down snug. After letting it set for about 30 minutes, I took it out for a test-ride. The whole bike works perfectly. Checking it after the ride, there was no looseness or any signs of stress.
I will check it from time to time to make sure it's holding, but as of now, I'm pretty confident it's a permanent fix.
Reply
#4
it is your bike......

just don't sell it or loan it to anyone; Liability Lawyer would love the $$$$$$.
Nigel
Reply


Possibly Related Threads...
Thread Author Replies Views Last Post
  Stripped & stuck nondrive crank bolt Timfoley 4 3,363 05-30-2013, 02:38 AM
Last Post: painkiller
  Stripped Out Chain ASwirsky 3 1,293 04-02-2013, 06:55 PM
Last Post: RBurrelli
  Stripped retaining bolt on right crank arm dcbriggo 4 6,879 06-03-2011, 04:28 PM
Last Post: dcbriggo
  Removing Pedals - stripped csmith 3 10,360 03-04-2011, 09:57 PM
Last Post: Darrenjs92ni
  Opinion on stripped threads in crank arm. JohnV 20 26,094 02-18-2011, 05:45 PM
Last Post: JohnV
  Crank Puller Failing to Pull Crank metellus 6 7,819 07-06-2010, 05:23 PM
Last Post: Billy
  Crank Threads stripped Thor 7 11,501 05-30-2010, 07:20 PM
Last Post: mcl896b
  I stripped my flats trying to remove my pedal ssavage666 2 7,592 05-19-2009, 09:38 PM
Last Post: DaveM
  Crank arm pedal threads are stripped antrossini 5 25,821 09-01-2008, 06:21 AM
Last Post: ozzzyrick

Forum Jump:



ISSN 1918-3445 © Copyright 2007-2010 Bicycle Tutor / Privacy Policy / Created by Alex Ramon

feed