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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?


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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 '14 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 '14 at 12:45
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 '14 at 13:28
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 '14 at 2:34

6 Answers 6

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 '14 at 13:23
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 '14 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 '14 at 7:13
Disagree! My LBS has helicoiled many a stripped crank arm. Last I checked the charge was like $20, which is relatively cheap considering the tools and time involved. – Suspended User Dec 2 '14 at 23:16

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? – YourConscious Jan 31 '14 at 9:19
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 '14 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 '14 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 '14 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 '14 at 1:06

Probably too late, but since you said it was just the first few threads, you could run the proper size tap in to clean up the threads. I found this while looking for info about bike pedals for a completely unrelated project, so I don't know the correct thread size, but if you know it, you can tap that out and good as new.

No need for helicoils or adapters, they would be plan B if the threads are totally shot and the tap can't clean them up. But I've cleaned up some really boogered threads with taps and dyes.

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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 '14 at 2:11
I would be skeptical whether such a product would hold up against the lateral loads presented with a pedal. – Daniel R Hicks Feb 1 '14 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 '14 at 7:09

Just fixed my grandsons pedal, borrowed 'thread restorer kit' from O'Reilly auto parts, leave deposit, 10 min fix, most auto parts stores do this.should work if first few threads are stripped

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Welcome to SE Bicycles! Could you add some more details to help others find the tool and visualize the process. Perhaps a photo of the kit, or at least at the specs on the insert you used or a bit more description of the parts/process involved. For example, does the tool restore existing threads (i.e., clean them up by running a tap through them to recut the damaged part) or did you enlarge the hole and then tap for and install an insert to replace the damaged threads. Thanks! – dlu Nov 4 at 15:28
Yes, on the O'Reilly auto parts site click 'free tool rental' and there a list of tools they loan, this was the Thread Restorer Kit, the kit has both metric and regular and sizes up to 5/8, also files if you have to bore out to a larger size, this was a childs bike, not the type your members use, and the first 3 threads were stripped and plenty of threads left. it also will redhread bolts, you do need wrenches, at least an adjustable, but a ratchet set is preferable – opalockafats Nov 4 at 19:06

If you're saying that only the first 3-4 threads are stripped, or at least not clear, you can try threading the pedal in from the opposite side. This might help to reform the first few damaged threads. If you have a tool to remove the pedal (6mm or 8mm allen key or 15mm pedal wrench) then this method shouldn't require any further tools.

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