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I'm attempting to reassemble my bicycle after it was shipped across the US. All is well; except one pedal cannot be screwed back in and it's because the inside of the pedal arm screw hole is stripped -- the pedal itself seems to be fine thread wise, but I cannot screw it into the pedal arm. I don't drive, and I live much closer to a home depot then a bicycle shop; I'm wondering if anyone has any repair suggestions? I bought a wrench to take the crank and arms off, but apparently I need additional tool too get it off; this was just an attempt at having more leverage to try and and screw the pedal in from a top. Anyone have any DIY suggestions? WD40, thread repair of sorts?

UPDATE: IT IS NOT COMPLETELY STRIPPED; JUST THE FIRST 3 - 4ISH AT ENTRY POINT. I PICKED UP SOME EPX CYCLE GREASE THIS EVENING, GONNA GIVE THAT A SHOT TOMORROW RE: SUGGESTIONS. CHEERS

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Stripped threads on disc brake mount pole are fixed by making a larger thread inside the hole and using a larger bolt. But the pedal's male thread is of fixed diameter, so this is not an option. Maybe some adapter e.g. M8 (or whatever the pedal is) to M10? Sounds crazy, though. –  Vorac Jan 31 at 9:05
    
Important question: Is this the left pedal or the right? If the left then you're probably SOL. If the right then it can be bored out and a "helicoil" installed (though this would need to be done by a skilled mechanic with the right sized helicoil). Probably you'll need to replace the crank arm. –  Daniel R Hicks Jan 31 at 12:45
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Given that you're trying to do the job without the proper tools, I'm assuming that you don't have a lot of experience with doing your own maintenance. And since you don't mention a visual inspection of the threads on the crank arm: are you sure you're using the correct pedal and turning it the right direction? The pedals are right/left specific and the left pedal is reverse threaded. –  jimirings Jan 31 at 13:28
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I think the net-net is this: Take it to a bike shop and bite the bullet. Either they can repair it or they will install a new crank arm. (And given your problem with the pedal I'd not suggest you attempt replacing the crank arm yourself.) –  Daniel R Hicks Feb 1 at 2:34

3 Answers 3

You can get parts to fix this, like the helicoil that work by cutting a new, larger thread into the crank then adding a spacer to bring it back to the correct size. They parts are relatively cheap, but the tool to cut the new thread is expensive. Which means that if you can find a bike shop with the tools it's going to cost quite a bit to have them do the work.

It's almost always going to be cheaper to simply find a second hand crank that fits, or if that fails buy a new crank.

As far as the rest of the tools, it might be worth buying a cheap bicycle tool kit rather than buying one tool at a time or travelling long distances to a bike shop. There are a number of specialised tools needed if you you're going to completely strip down a bike, and buying them one at a time adds up. My suggestion is buy the cheap-but-reasonable-quality set, then as you wear out the tools replace them with decent ones. That way the tools you barely use or where the cheap tool works well enough never get replaced.

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I'd vote this up twice if I could because of the suggestion to get a cheap tool kit. I bought one about 10-15 years ago and it's still the core of my tool kit. I've replaced some of them with nicer ones, but that's always been because the nicer ones were easier to use than the cheap ones (e.g., the crank extractor in the cheap kits is functional, but incredibly awkward), not because I wore them out. –  jimirings Jan 31 at 13:23
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Cheap tools are fine if you're not running a shop =). But I do agree with the new / used crank suggestion more than trying to fix it given the likely costs associated with it. –  Batman Jan 31 at 17:18
    
Ditto. Repair attempts will cost more than they're worth in the long run as compared to a replacement crank. –  Carey Gregory Feb 1 at 7:13

If all the thread is stripped, there is not much you can do (I saw on the forum here, that you can weld it inside, then make new thread). If only the start of the thread is stripped, try the next:
1. put a little grease inside 2. screw the pedal from the other side of the arm (i.e. the pedal will be below the BB) to the end 3. unscrew the pedal, and insert it in the right position. It can correct the thread.

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Yeah, not all of it; just the first some. Cool, yeah, I'll try this tomorrow - grease? What kind of grease should I purchase? –  Frank Milo Jan 31 at 9:19
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Typically bike applications use a light lithium grease as a lubricant. In fact, I would put a dab on the pedal threads every time you remove and re-install your pedals. This would be the same grease you would use when you repack hub, bottom bracket or headset bearings. –  Gary.Ray Jan 31 at 13:16
    
Interesting idea and could work if the damaged threads are a bit inside the crank arm, but if they're the first thread or two (which is usually the case), probably won't work since the pedal won't reach them. –  Carey Gregory Feb 1 at 7:16
    
@CareyGregory usually the pedal is reach the end of arm. Then you have to very carefully insert the pedal the right way. –  Alexander Feb 1 at 16:55
    
@Alexander Your reverse-threading technique totally worked for me. My first 2-3 crank threads were stripped and my pedal threads would not catch. I screwed the pedal in from the opposite side and then removed it and tried the correct side. Worked like a charm. Thanks, amigo. You saved me the price and hassle of finding new cranks. –  user13029 Jul 18 at 1:06

Loctite makes a product called Form-A-Thread part #236382. The kit contains an epoxy and a release agent that forms the new threads using the pedal threads as a mold. I have never used it on anything as large as a pedal. It is also not a cheap repair as a kit can cost upwards of $30. Checking the prices of an oversized tap and helicoil or repair bushing kit your local shop should be able to repair for less than you buying the tools. I am all for buying tools and doing my own repairs but this is hopefully a once in a lifetime repair. It doesn't make financial sense to buy the tools.

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They sell similar things in automotive shops for things which size of a pedal, so I could see this plausibly working. –  Batman Feb 1 at 2:11
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I would be skeptical whether such a product would hold up against the lateral loads presented with a pedal. –  Daniel R Hicks Feb 1 at 2:33
    
Have to agree with @DanielRHicks here. No way such a product will hold up long enough in this application to make it cost effective. –  Carey Gregory Feb 1 at 7:09

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