# Threads gone on crank arm - pedals won't screw in



## BobHatcher (Jan 23, 2008)

I've got a 15-yr old Trek mountain bike that I've put road tires on and use as a beater bike around town. It's probably not worth very much, but it fits me and I like it.

I've been using it on a wind trainer this winter and noticed that my foot was wobbling and when I checked it seems the pedal had become unscrewed from the crank arm. Upon inspection the crank arm threads are shot.

I'm looking for advice on how I can fix it. As far as I can see, here are my options


Take it to a machine shop and see if they can rethread it with a tap and dye.
Replace the crank arm - but, I've never done this before and the number of threads with people having trouble with this scares me.
Take it to the LBS and have them replace either the crank arm (if possible) or the crank set itself.

But, given that the bike isn't worth it, I am not sure i want to replace the entire crankset. How likely is it that I'll just be able to replace the crank arm itself?

What advice would you give?

thanks,

bob


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## Cory (Jan 29, 2004)

*They still make helicoils?*

Back when I used to pass my time crossthreading spark plugs into the aluminum head of my race car, there were inserts called Helicoils (brand name; there probably are others) that could be run into the stripped hole and provided threads for whatever screwed into it. Looked like a stainless steel spring, sort of, and made a permanent repair.
In your case, though, it might be cheaper to pick up an old bike in a thrift shop and swap cranks, or even buy a new crankset from someplace like Nashbar. I'm always surprised these days when I check the prices on stuff I used to pay $1.75 for (for example, the price of a VW engine rebuild the first time I had it done, in the mid-'60s, was $90. Ninety, not $900).


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## flakey (Feb 8, 2003)

There is a repair kit for this that a professional shop should have. The tool reams and threads the crankarm and then you install a threaded bushing which will accept your 9/16 pedal. The bushing is like a helicoil except that its more like a threaded barrel.
I would guess the insert would cost about 5 dollars retail. Not sure about labor, maybe $15-20.00 

It's been 10 years since I worked at a shop and did this so I cant remember how long it takes.

The tool/repair kit is made by ELDI


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## tihsepa (Nov 27, 2008)

http://www.youtube.com/watch?v=RvmL0pEphQI

I fix alot of stripped threads. These are easily the best way and it sounds real familiar to what flakey had mentioned.


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## BobHatcher (Jan 23, 2008)

Hey, thanks a lot you guys. I think I'll go to my local car mechanic and see if he'll re-thread for me.

I appreciate it.

bob


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## flakey (Feb 8, 2003)

I would first call some bicycle shops in your area and ask them if they have the ELDI tool and repair kit. The tool is specifically designed for this repair as well as the threaded bushing that is inserted into the arm. If they have the tool, that means they have probably done it a few times.

Your auto mechanic could probably do it, but if its the right drive side arm, does he have a 9/16 left hand threaded helicoil? If he can get them, then you/he will have to probably buy a box of 6 or 10.
Also a helicoil may not be the best choice. The ELDI kit has a threaded barrel where a helicoil is more like a spring. 

It will be a pain for your auto mechanic to do this while the crankarm is attached to the bike, a shop would remove it and then do the repair. 

Another thing is that if a shop screws up the repair, they will probably give you a new arm or a very good deal on a new one.

Starting with a bicycle shop would seem to be the best first choice.


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## JCavilia (Sep 12, 2005)

> but if its the right drive side arm, does he have a 9/16 left hand threaded helicoil?


Good point, except you mean LEFT side arm.


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## fleck (Mar 25, 2005)

any good bike shop should have the capability toe ream the threads. I had it done on my CX bike this past fall after tearing it up. It's been great since.

I wouldn't bring it to a mechanic unless no shop around could do it.


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## BobHatcher (Jan 23, 2008)

Thanks everyone... yes, my LBS can re-thread it for me.

I appreciate all your comments... thanks.

bob


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