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  1. #1
    Bro
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    Could a crash strip pedal/crankarm threads?

    I was switching out pedals on my fixed gear earlier. Took the old ones off without issues, new pedal wouldn't thread in easily on the left crank. Tried, tried again, kept trying... I finally decided to look at the threads, and it turns out that one or two threads in the middle of the crank are stripped.

    And that's the confusing part -- I haven't switched pedals on that bike in months, and when I last put pedals on the bike, they went on without issues. When I was installing the pedal earlier, I greased up the threads and threaded it into the crank by hand, as I always do. But then I realized that that bike has hit the pavement several times, on the same side as the stripped crank. I use the bike as my commuter, and on those occasions that I crashed, I hit a patch of ice, and the bike went down.

    So that's my question -- does that sort of low-speed crash have the potential to move a pedal within the crank enough so that the threads are damaged? I wouldn't expect it to, but on the other hand, I don't know what else could have damaged the threads.
    I've made some bad decisions like taking the gears off my bike. So here's the warning: Do not as I say, nor as I do.

  2. #2
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    I'm no expert, but that sounds unlikely to me.

  3. #3
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    If the pedal was loose when the crash occurred, then yes the crash can cause damage to the threads as the pedal will move relative to the crank and take the threads with it. If the pedal was tight in the crank when the crash occurred, then no the crash will not cause damage unless it was a major crash, in which case more than just damaged threads will be evident.

  4. #4
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    Quote Originally Posted by Bro View Post
    So that's my question -- does that sort of low-speed crash have the potential to move a pedal within the crank enough so that the threads are damaged?

    If the pedal was tight no way, and even if it was a little loose I don't see how that would be possible. I'd bring it to a bike shop and have them run a pedal tap through it.

  5. #5
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    Quote Originally Posted by J.B. Weld View Post
    If the pedal was tight no way, and even if it was a little loose I don't see how that would be possible. I'd bring it to a bike shop and have them run a pedal tap through it.
    Pretty much what JB said. A tap will fix your problem.

  6. #6
    Bro
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    Yeah, I was already planning to have the LBS run a tap today. I'd been planning to tap it myself until I saw how expensive pedal taps are. It's just a mystery to me how the threads got damaged in the first place -- I tighten my pedals to "tight enough" with an Allen key or pedal wrench. Oh well. Stuff happens.
    I've made some bad decisions like taking the gears off my bike. So here's the warning: Do not as I say, nor as I do.

  7. #7
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    A buddy of mine clipped a rock and it stripped the threads from his crank. The pedals were relatively snug prior to the ride - I had lubed his chain for him in the parking lot and didn't feel any wobble when I pedaled the bike. When he hit the rock it wasn't bad enough to make him crash but it was bad enough to destroy his crank.

    So yes, a minor crash is enough to damage the crank threads. You may have to use a helicoil - a good shop will know what to do.

  8. #8
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    I've seen plenty of crashes that have destroyed crank arms at the pedal threads. Most of the time in carbon cranks it just rips the pedal insert out. But in all of these cases the pedal received severe damage as well.

  9. #9
    Bro
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    Quote Originally Posted by jtmartino View Post
    A buddy of mine clipped a rock and it stripped the threads from his crank. The pedals were relatively snug prior to the ride - I had lubed his chain for him in the parking lot and didn't feel any wobble when I pedaled the bike. When he hit the rock it wasn't bad enough to make him crash but it was bad enough to destroy his crank.

    So yes, a minor crash is enough to damage the crank threads. You may have to use a helicoil - a good shop will know what to do.
    That reminds me -- I've also clipped the left pedal several times on a downhill corner near my house -- the bike is a fixed gear, so it's a bit harder to control pedal strike. One strike in particular sent the bike into the air, with me still on it. I'm fairly certain that I'd changed pedals at least once since then before finding the damaged threads the other day, but that pedal strike may have weakened the threads, which then became damaged after repeated pedal removal/installation.

    The pedals that were in for the pedal strikes are just typical BMX-style platform pedals, and the outer edge of the pedal from the damaged crank is definitely torn up quite a bit.

    Anyways, I got the crank tapped at my local shop yesterday. It still looked fairly questionable after they finished, but I installed my pedals without issue and took it for a quick ride today, and I haven't noticed any problems yet.
    I've made some bad decisions like taking the gears off my bike. So here's the warning: Do not as I say, nor as I do.

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