Have questions or want to discuss cycling? Join Now or Sign In to participate in the BikeRide community.

New: Take Part in the September Giveaway to Win the Luckeep X1 Pro ebike


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, 05:07 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
 
31,317
07-19-2021, 12:00 AM
Last Post: rbx
 
22,582
06-06-2015, 06:53 PM
Last Post: garrett01
 
17,534
05-06-2015, 01:38 AM
Last Post: eastman
 
6,713
04-02-2013, 02:55 PM
Last Post: RBurrelli
 
7,717
06-14-2012, 09:43 PM
Last Post: FredS
 
21,659
06-16-2011, 07:53 AM
Last Post: Bill

Forum Jump:

[-]
10 Latest Posts
Northeast of India or Myanmar rides
Today 01:36 AM
New from South Florida
Yesterday 12:31 PM
Newbie from DC
10-12-2024 08:29 PM
Best Accessories for Polaris Ranger 1000...
10-12-2024 07:16 AM
Naming a bicycle - Yes or No?
10-12-2024 02:11 AM
Ketone Ester $$$
10-11-2024 05:55 PM
Energy gels for cycling
10-11-2024 05:52 PM
Change comes hard in the cycling communi...
10-11-2024 11:30 AM
COLNAGO SUPER (unknown year)
10-11-2024 08:12 AM
Broken Bottom Bracket
10-11-2024 01:26 AM

[-]
Join BikeRide on Strava
Feel free to join if you are on Strava: www.strava.com/clubs/bikeridecom

[-]
Top 5 Posters This Month
no avatar 1. Jesper
26 posts
no avatar 2. GirishH
21 posts
no avatar 3. meamoantonio
15 posts
no avatar 4. Flowrider
13 posts
no avatar 5. Painkiller
10 posts