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

New: Take part in the October Giveaway for the Haven Bicycle Co. beach cruiser


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
 
18,913
07-19-2021, 12:00 AM
Last Post: rbx
 
1,304
11-11-2020, 09:52 AM
Last Post: Jesper
 
4,769
03-23-2016, 02:03 PM
Last Post: darreng
 
16,126
06-06-2015, 06:53 PM
Last Post: garrett01
 
12,348
05-06-2015, 01:38 AM
Last Post: eastman
 
16,051
08-24-2014, 10:46 PM
Last Post: 1FJEF

Forum Jump:

[-]
10 Latest Posts
What was your first bicycle?
Today 10:35 AM
Chain skips under heavy load when pedall...
Today 06:03 AM
V Brakes just won’t adjust properly
Today 05:59 AM
Bike evaluation
Today 01:05 AM
VINTAGE DERAILLEURS: Campagnolo 50s-80s
Today 12:52 AM
[Sponsored] Souke Sports Cycling Apparel...
Yesterday 11:25 PM
What's your No.1 concern when you purcha...
Yesterday 11:24 PM
Is this frame dent a concern?
10-13-2021 04:50 PM
Looking for Cycling Apparel Testers - So...
10-12-2021 10:10 PM
Cycling Training Programs
10-12-2021 04:54 PM

[-]
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. Souke Sports
22 posts
no avatar 2. Criminal
17 posts
no avatar 3. ReapThaWhirlwind
12 posts
no avatar 4. Zviedrs
7 posts
no avatar 5. JR Namida
7 posts