Bicycle TutorBicycle Tutor

Show off your bike!

Related video tutorials:
Crank arm pedal threads are stripped
#1
It's an aluminum 3 piece crank, it is kinda faded but I think it is an SR Suntour if that means anything. It came on a Trek 3700 purchased in late 2006 or early 2007...
When I was riding it, it would loosen up... and I'd tighten it with my fingers as good as I could... but it wouldn't work too well for long rides... one day it fell out and it stripped the threads inside the right hand crank arm.
So I was wondering if there was any way to re-thread the hole... or buy a new arm... or something that is a fairly inexpensive fix. I can't afford a brand new crank.

Reply
#2
There is a product called a helicoil. First you have to drill and tap the crank arm to a larger diameter so the helicoil can be threaded in. Some shops will do this for you, but often the cost is more than it would be to replace the crank arm.
Reply
#3
How do I tell what size to buy?
Do most bike shops have them or do I have to order them off the site?
What does tap mean?
How much would a new crank arm be?

Reply
#4
Quote:How do I tell what size to buy?
To be honest I'm finding a lot of conflicting info online about the correct size to use. You likely have 9/16" pedals... I'll keep looking for more info. When I worked in the shop we always had a guy named Max who took care of helicoil repairs.
Quote:Do most bike shops have them or do I have to order them off the site?
A good bike shop should have one, or at lease be able to assess whether or not it is worth doing...
Quote:What does tap mean?
A 'tap' is a tool that cuts new threads inside a hole. Here's an article that describes the process.
Quote:How much would a new crank arm be?
You're probably looking at somewhere between $10-$30 for a single crank arm. Your best bet would be to take your bike down to the local bike shop to find a proper sized replacement.

Reply
#5
Hi,
I have some problem with my Trek 3700 approximetly 2 years old. I think this staff is defective. I have found on internet a complete crankset for $99 but only in stores not shipping is available. Right now I am looking for a bike shop around to get an estimate? Pain in the ...., If you find some good solution please let me know.
Thank you,
Anton

Reply
#6
Hi Antrossini,
I'm familiar with the Helicoil re-threading and to be honest it will be expensive unless...
You know someone in the engineering business. I would look for a small engineering business that may have a helicoil repair kit.
To do it yourself requires perfect alignment of the original thread bore, using a special sized drill and tap for the helicoil and a specific tool for setting the new thread, which is stainless steel.
If you can get it done cheaper than a crank arm replacement the new thread will be stronger than the original.
Regards,
Rick.

Reply


Possibly Related Threads...
Thread Author Replies Views Last Post
  Stripped Crankarm garrett01 10 7,185 06-06-2015, 10:53 PM
Last Post: garrett01
  Threaded Left Crank Arm (Pedal thread) square_eyes 7 5,135 09-29-2014, 11:03 AM
Last Post: square_eyes
  Thread busted on right pedal crank zippy 35 64,329 06-10-2014, 04:21 PM
Last Post: emmanuelr
  Stripped out crank arm Gideon Reynolds 3 7,368 10-22-2013, 04:26 PM
Last Post: nfmisso
  Crank brothers pedal rebuild peter o'sullivan 0 1,872 10-22-2013, 12:45 PM
Last Post: peter o'sullivan
  First bike restore... pedal crank issue, see pics liveanimal 7 6,137 10-15-2013, 02:55 AM
Last Post: nfmisso
  Stripped & stuck nondrive crank bolt Timfoley 4 5,888 05-30-2013, 02:38 AM
Last Post: painkiller
  Stripped Out Chain ASwirsky 3 2,482 04-02-2013, 06:55 PM
Last Post: RBurrelli
  JB Weld pedal-to-crank arm experiment Wolfie 2 10,590 07-07-2011, 03:35 PM
Last Post: nfmisso
  Stripped retaining bolt on right crank arm dcbriggo 4 11,604 06-03-2011, 04:28 PM
Last Post: dcbriggo

Forum Jump:



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

feed