Help with a stripped pedal hole, on a crank arm, please.

[Archie Sturmer]

Wald once made a crank repair kit that consisted of a bolt threaded from the back of the crank arm and extended into a threaded sleeve (extension-like) into which the pedal would also be fastened.

Not sure, but they may have come in 9/16” as well as 1/2”?

Wald USA Bicycle L & R Extractor Puller Vintage Antique Bike Shop Tools | eBay

Wald Tools. Made In USA. Lh & Rh Extractors.

www.ebay.com

 

[eastema]

Helicoil is a fairly cheap and solid fix.

 

[byke!punk]

An age old problem. This image is from a Harley catalog. I don’t recall where I got my set.

 

[Schwinn Sales West]

Have any of you ever ridden a bicycle with a bent crank arm, or a bent pedal spindle, it's a weird feeling. Having the pedal spindle exactly on alignment with the bottom bracket bearings is very important. Installing a "right hand thread" Heli Coil or welding up the stripped pedal hole in the crank arm is not very difficult, that is until you consider how easily it is to get the new hole and threads "out of center". This kind of repair work would require a mill and some degree of operator skill to set it up.

At the end of the day, it would be much faster, and much cheaper to replace the damaged crank arm. Curious, how do you strip the threads out of a crank arm? Was the pedal ridden loose?

John

 

[byke!punk]

At the end of the day, it would be much faster, and much cheaper to replace the damaged crank arm.

John

Yep!

 

[Dannuus]

I have an alloy drive side crank arm with a stripped pedal hole. Re-tapping the hole won't work as the hole is too big now. Other than replacing the crank arms or using a heli-coil , is there anything else that can be done to remedy this problem? Thank you

Nope.

 

[Fritz Katzenjammer]

When I worked at a place that had a machine shop attached we didn’t think anything of welding something like this up and remachining it, but we were recovering parts worth a lot of money. You’ll likely be looking a couple hundred dollars to have something like this done right.

Likely a lot cheaper to replace the component.

 

[Andrew Gorman]

Unior makes pedal repair bushings. It's a simple job that I have done myself. You don't need their reamer or tap, just the bushing. Drill out the messed up hole to the pilot drill size for the tap. tap the hole, insert the bushing with loctite, trim off any excess and you are on the road. The whole kit is available and would probably save time if you were doing this frequently.

Unior Pedal Thread Insert - Right, 9/16''

- Pedal thread inserts are used to replace damaged threads in cranks, sold individually

www.cyclesport.com

Unior Crank Saver Kit 1695MB1

www.starbike.com

 

[eastema]

Have any of you ever ridden a bicycle with a bent crank arm, or a bent pedal spindle, it's a weird feeling. Having the pedal spindle exactly on alignment with the bottom bracket bearings is very important. Installing a "right hand thread" Heli Coil or welding up the stripped pedal hole in the crank arm is not very difficult, that is until you consider how easily it is to get the new hole and threads "out of center". This kind of repair work would require a mill and some degree of operator skill to set it up.

At the end of the day, it would be much faster, and much cheaper to replace the damaged crank arm. Curious, how do you strip the threads out of a crank arm? Was the pedal ridden loose?

John

I mentioned helicoil I guess because I am a machinist and have a Bridgeport mill in my cellar. In industry this is a very quick and easy fix. But you are right, you would do this job with the chainring lock nut fastened tight, indicate chainring flat and then machine the hole to proper size for helicoil. I forget the days when I didn't have these skills. I am 61 now.

 

[Schwinn Sales West]

I mentioned helicoil I guess because I am a machinist and have a Bridgeport mill in my cellar. In industry this is a very quick and easy fix. But you are right, you would do this job with the chainring lock nut fastened tight, indicate chainring flat and then machine the hole to proper size for helicoil. I forget the days when I didn't have these skills. I am 61 now.

I mentioned helicoil I guess because I am a machinist and have a Bridgeport mill in my cellar. In industry this is a very quick and easy fix. But you are right, you would do this job with the chainring lock nut fastened tight, indicate chainring flat and then machine the hole to proper size for helicoil. I forget the days when I didn't have these skills. I am 61 now.

If you were to take the time to set up the crank arm for the proper drilling and taping by using a mill for alignment, a Time-Sert installation would be a better thread repair than a Heli-coil in an aluminum crank arm. The Time-Sert gets locked into the hole and cannot unscrew like a Heli-Coil. Lots of motorcycle case threads come with the steel Time-Sert threads original from the factory on high stress thread points. I can't think of many more high stress thread points than on a steel pedal threaded into an aluminum crank arm.

Fortunately, on this repair the original poster is discussing a right-hand thread. If the problem thread, was on the left crank arm he would have far less thread repair options.

John