4

I got a brand new bike and I wanted to replace the pedals with the ones from my old bicycle. However, while removing the pedals from the new bike, I forgot that one of the threads was reversed and accidentally tightened it further.

I was using a 15mm wrench and went full strength until I eventually realized it was the other side and stopped. Is it possible that I exerted enough torque to damage the crank / bottom bracket?

Also, I tried riding it later and didn’t notice anything strange, but is it possible that I caused some damage, that it is not noticeable now, but will show up in the future?

Improve this question

1 Answer 1

Reset to default
8

Torque for a pedal into a crank is ~40 Nm which is quite significant. A traditional 15mm pedal wrench does not provide a lever long enough that would make it easy to go way beyond that by hand. There should also be no damage to the bottom bracket as the pedal screws into the crank.

You can always unscrew the pedal and inspect the threads inside the crank to make sure.

Improve this answer
4
  • I see. I was concerned I caused damage to the other end of the crank, where it connects with the bottom bracket axis. Supposing I had the wrench parallel to the crank, which has 15cm arm, the lever would be quite long, thus the torque on the bottom bracket axis quite large. I thought it would be ok since that part is supposed to withstand high torques while pedaling, but I was preventing the cranks from moving, which is not the usual condition when torque is applied.
    – fabda01
    Apr 23 at 23:55
  • 2
    @fabda01 If you had the pedal wrench parallel to the crank arm on which you were screwing the pedal in such a way that the lever is the length of that crank arm + the length of the wrench while having your other hand on the other pedal to prevent the crankset from rotating, that would result in a poor mechanical advantage which would be quite a limiting factor in terms of the torque you could apply. Also, the torque at the axle would still be limited by the force needed to prevent the crank arm from rotating on the other side.
    – olliebulle
    Apr 24 at 1:19
  • 1
    @fabda01 consider standing on both pedals to go over rough ground. Then you have 50% of your bodyweight applying torque to each crank arm without it moving (but rough ground means shock loading, so the forces are actually far higher). For your pedal spanner to exert this same torque, assuming it effectively doubles the lever, you'd still need to apply 1/4 of your bodyweight - and half your bodyweight to hold the other side static. It seems unlikely that you could do this with your hands
    – Chris H
    Apr 24 at 12:50
  • 1
    BTW I tend to undo pedals by putting the spanner nearly parallel to the crank arm, such that squeezing them together loosens the pedal. Then wrap both hands round both cranks and spanner, and squeeze hard. That way when it moves suddenly, I don't.
    – Chris H
    Apr 24 at 12:52

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge that you have read and understand our privacy policy and code of conduct.

Not the answer you're looking for? Browse other questions tagged or ask your own question.