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Bicycle crank repair

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Bicycle crank repair

Postby paul_s » Fri Mar 03, 2017 2:57 pm

I got a bicycle from a neighbor that has a pedal stripped out. I'm looking for suggestions on how to repair it. I don't know what type of aluminum it is. What filler rod would people suggest? I'm thinking that I would weld the entire hole and re-drill and tap it. I've never made this type of repair and feel that there would be some ideas from folks that have done this before.
Thanks for your suggestions.
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Re: Bicycle crank repair

Postby ldbtx » Fri Mar 03, 2017 3:14 pm

You sure that's not a steel nut contained in the casting? Kinda looks that way. Either way, I'd be tempted to Heli-Coil it, I think.
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Re: Bicycle crank repair

Postby AndersK » Fri Mar 03, 2017 3:26 pm

Just have in mind that side has a left hand thread.
Might have contributed to the failure... :mrgreen:
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Re: Bicycle crank repair

Postby Artie F. Emm » Fri Mar 03, 2017 3:31 pm

I did a quick look, but didn't learn what alloy a crankset usually comes from. I believe there is a particular filler metal to use if you're not sure of the base alloy- someone will come back with that info, I'm sure.

In the mean time: do you already have the taps required for this? It may be a specialized deal specific to the cycling industry. BTW The left-side pedal has reverse threads to prevent the pedal from un-threading itself while riding. I saw the proper taps from Park Tool for $35. And looking at how worn the teeth are on those chainrings (the tops start out life as square), I looked up replacement cranksets at Nashbar.com and they start at $30. If the threads are too badly FUBARred to use and the bike just isn't worth the time and effort, you might consider just welding the spindle into place (if the metals allow).

What's the make/model for your bicycle?
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Re: Bicycle crank repair

Postby paul_s » Fri Mar 03, 2017 4:21 pm

The bike is a Ascent Diamond Back. The crank has a part number Shimano FC-M450. It's all alloy and not with a steel insert...but that would be much stronger.
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Re: Bicycle crank repair

Postby paul_s » Fri Mar 03, 2017 4:47 pm

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Re: Bicycle crank repair

Postby Erich » Fri Mar 03, 2017 5:40 pm

Left side crank will have a left handed thread. It will be an odd combo of diameter and thread.
Don't start or price the job until you have the tap in hand.

I don't want to make a filler recommendation because I don't know the alloy but for sure that part is heat treated up to T6 temper. You will need to have the part re heat treated after welding if you don't want further failures.

If you could find a helicoil for that thread that would be the easiest way to go.

Here are pedal taps
http://www.chainreactioncycles.com/us/en/park-tool-pedal-tap/rp-prod17511?utm_source=bing&utm_medium=cpc&utm_campaign=Chain%20Reaction-US-PLA-PLA-All-SE-Bing%20Shopping&utm_keyword=Park+Tool-Workshop+%3E+Tools&utm_term=1101204465508&utm_content=Bing%20Shopping&gclid=CJmHs4Wlu9ICFQaXMgodjSwEiQ&gclsrc=ds

Well, how about that, there are repair bushings

http://www.parktool.com/blog/repair-help/#article-section-1

Put down the torch and Step away from the welder and use the bushing repair kit.
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Re: Bicycle crank repair

Postby Poland308 » Fri Mar 03, 2017 7:43 pm

Bike info = Zank.
I have more questions than answers

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Re: Bicycle crank repair

Postby exnailpounder » Fri Mar 03, 2017 7:58 pm

The left side has reverse threads :lol:
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Re: Bicycle crank repair

Postby AndersK » Sat Mar 04, 2017 5:37 am

exnailpounder wrote:The left side has reverse threads :lol:

Yeah, I got it wrong. Stand corrected in shame :oops: :lol:
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