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I was riding home today (with clipless pedals; SPD) and noticed my ankle was twisting strangely with each rotation of my legs. I had just gotten to the top of a massive hill. I pulled off to the sidewalk and inspected my pedal.

Turns out that the pedal had begun to loosen (perhaps it was never tight enough?) and the force of me pedaling on it had bent it a bit. I was quite upset because I was still 20 minutes away from home.

I tried getting the pedal off, but I was unable to loosen it (with a wrench, or hex key from the side) What should I do? I'm thinking of taking a powerdrill and forcing it out. Will this be an okay solution? Will my crank arm be damaged at all?

Here is a picture enter image description here

as you can see the bend is very imperceptible. You can really tell when you pedal on it though. From the picture you can also see how loose the pedal got when it started to bend. Do you guys think there is hope in saving the crank?

Thanks for the advice guys, I'm going to take this to my LBS and see what they say. I'll let you know what happens!

EDIT: Turns out that the pedals were not installed tight enough and it resulted in some cross-threading. My LBS said that the crank wasn't damaged too much. He re-threaded the crank and said that it should be okay, but that I should watch out in case that happened again.

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  • It seems a bit odd that you can't get the pedal OFF. Are you sure you're turning it in the right direction? The left pedal threads backwards, remember.
    – Daniel R Hicks
    Aug 9, 2014 at 1:16
  • Stupid question: Is is possible that the crank arm is bent, due, perhaps, to dropping the bike on the pedal? Or perhaps due to climbing a steep hill with a fixie when the pedals or cranks were not up to that much force?
    – Daniel R Hicks
    Aug 10, 2014 at 14:16
  • I did not think about that. I guess that is possible. The bike has fallen down quite a bit. I'm going to my LBS in a few minutes and will figure it all out then.
    – bdeonovic
    Aug 10, 2014 at 17:50
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    A happy ending! I'm embarrassed to admit, I had the same experience when I assembled a bike and was in a hurry to go for a ride and didn't seat the peddle all the way. The peddle felt 'wonky' like you described - fell off - and I was able to clean the crank threads and re-attach. I'm an idiot. Want to know how much of an idiot? I'm still using the same damaged crank, pounding uphill on 18% grades.
    – Jim Fred
    Aug 10, 2014 at 23:59

4 Answers 4

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As others have pointed out, it's probably not so much bent but cross-threaded. The threads fatigued because the shoulder on the pedal shaft wasn't seated on the crank arm. If you keep riding it as-is (not suggested) the pedal will fall off all by itself!

One thing in your favor: judging by the ~3mm gap between the shoulder and the crank arm, you might have about 3mm of un-molested threads on the crank arm. When the pedal comes off, you can do as Blam suggested and run the pedal through from the inside to clean the damaged threads on the crank arm. Lubrication helps. As Nathan pointed out, it's very likely that the softer crank threads gave-way to the harder pedal threads. When re-installing the pedal make sure the shoulder on the pedal shaft seats firmly on the crank arm. It might hold long enough to arrange for a new crank arm.

Why did it fatigue and why will it hold now? If the shoulder on the pedal shaft is not seated, the threads will alternate between compression & tension which worsens fatigue. If the shoulder is seated, all the (remaining) threads are in tension working together. And, there's a moment/torque principle involved too.

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    I definitely WOULD NOT reinstall that pedal. Not unless the threads were proven to be perfect on very close inspection.
    – Daniel R Hicks
    Aug 10, 2014 at 12:49
  • Was it installed cross threaded, or did it work loose, damage thread then cross thread as it self tightened? (Pedals tighten under load). OP does not provide detail of recent maintenance, but absence of that detail makes me think the pedal was fine for a while - i.e. not cross threaded.
    – mattnz
    Aug 11, 2014 at 1:46
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Generally speaking, when a pedal works its way loose and is ridden for a decent amount of time, it does strip (and thus ruin) the crank arm. The only way you can be sure that the crank arm is good is to inspect it. So I'd guess your crank arm is damaged (especially if its at the point where you can't loosen the pedal).

A picture of how its bent in would be helpful, but theres a decent chance that both parts will have to be written off.

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I've had something similar (but more dramatic) happen and I lost the crank arm. It seems to be made of softer medal, luckily, than the pedal, which was absolutely fine and I still use. Crank arms are pretty cheap when compared to pedals anyway.

The damage may all be to the crank arm. I agree with Batman, the crank arms is probably a write-off. But it's probably the case that your aluminum crank arm came up again your tempered steel pedal and the latter's threading has decisively won. Which is all for the best.

I would say whatever your course of action, don't risk the pedal for the crank.

Removing a stuck pedal

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Hit it with a bigger wrench. Right side should have normal threads.
CNC Pedal Rod

I would try a bigger wrench before drilling it out. You have to drill exactly in the center. You will need a press.

If the pedal bent there is a pretty good chance crank was damaged. If the threads are just marred up a bit you might be able to clean them up by running a fresh pedal through from the inside.

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  • A bigger wrench was indeed all that was needed to get the pedal off.
    – bdeonovic
    Aug 10, 2014 at 23:19
  • If you needed a bigger wrench, the forces involve will have damaged the aluminium around the thread. You will not be able to achieve a 100% reliable repair without spending more than the crank arm is worth. Know what happens when pedals come off at high speed, I would not be using that crank arm.
    – mattnz
    Aug 11, 2014 at 1:43

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