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Is there something I can do to prevent my bike pedals from wearing out? And what causes the threads on a bike pedal to wear out?

I have a 4 year old Raleigh road bike with just regular open pedals. After 300 miles of riding, I had to replace the pedals because one of them broke off when the threads on the arm that the pedal screws into wore out.

The bike repairman offered to send the pedal out to be re-threaded but that would have taken a week and cost more than just replacing the pedals.

Any suggestions or recommendations?

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Thanks everyone. I really appreciate you taking the time to answer my question. – Jim Sandiford Jun 16 '12 at 5:38
There is one other slight possibility -- that somehow old French pedals were installed in a bike with "standard" pedal threads. The French pedals have threads with a slightly smaller diameter. – Daniel R Hicks Jun 16 '12 at 13:27

Having never had this happen, and having had one bike for over twenty years, I can only think that the pedal must never have been tightened up properly, so it was moving and wearing out - otherwise the pedal/crank connection is actually pretty solid.

It is something that can be hard to tighten, especially as one thread is clockwise and one counterclockwise, which can confuse people.

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It probably means that the pedal was never installed correctly: either it was not tightened enough or it was cross-threaded.

It's actually not that hard to install a pedal incorrectly. If you miss perfectly aligning the threads, it's called cross threading. It's possible to cross thread the pedals and still have them feel like the pedal look like it is installed properly.

However, if you look closely, you'd see that the pedal isn't perfectly perpendicular to the crank. When you pedal, you'll feel a pop as the pedal goes around when your foot crests and the pedal (due to not being parallel to the crank) has to change orientation.

Over time movements of the pedal relative to the crank will slowly strip out the threads on the crank, on the pedal, or both.

I could speculate that your raleigh may have been purchased at a department store, and that it wasn't assembled by a professional. They didn't install the pedal correctly.

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I had this happen. And it dug a concave gap into the crank arms. Expensive error to make. – geoffc Jun 15 '12 at 21:25

I would guess that the pedal was cross-threaded. Either that or it simply wasn't properly tightened to begin with. (In fact, a right-hand pedal may have been force-fit into the left crank or some such.)

In any event, the crank arm (in addition to the pedal) is likely damaged beyond use. The only possible repair of the crank arm is to install a "Helicoil" repair kit, if one can be found of the correct size (and rotation).

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