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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
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    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
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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
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    @geoffc not necessarily the most expensive fix of a new crank... I did this and took my crank to my shop. The shop drilled out the worn threads completely, then re-drilled the crank and used a double threaded "plug" to bring the threaded size back down to the diameter of the pedal threads. ~$30 fix on a Sram Force crank is worth it. Granted I made a dumb mistake that I should of avoided if I paid attention... – Nikolai Oct 28 '16 at 14:37
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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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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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In my experience the best way to fix/prevent that issue is before you install the pedals make sure to apply a water proof grease like this to the threads. Marine Grease

It costs about 3 dollars and will ensure that the threads will be less likely to cross thread and most importantly the pedals won't seize or stick to the crank arm the next time you change out the pedals.

If the damage is already done you can buy a 9/16" 20 tpi die to re-thread the pedal like in the image below and a 9/16" 20 tpi tap to re-thread the crank arm.

9/16" 20 tpi die

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    If the threads are worn because the pedal was loose, retapping won't help. Only a helicoil. – RoboKaren Oct 6 '16 at 14:57
  • @RoboKaren You're right, depending on the amount of wear. My answer is dependent on the fact that the extent of the wear isn't accurately described since the "bike repairman" decided the pedal needed to be rethreaded and said nothing about the crank arm and the idea that they were probably cross threaded in the first place. – npsantini Oct 6 '16 at 15:43
  • I've been looking for these tools, and while taps are accessible, the right dies are rare and expensive. Same goes for pedal helicoil-style repair kits. This is because bicycle pedals use 9/16" with 20tpi whereas the common National Fine spec is for only 18tpi. An 18TPI thread is incompatible with a 20TPI thread. – Criggie♦ Sep 22 '20 at 23:41
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Generally, the bolts one should use are titanium bolts. They do not wear out easily and they will last for ages! The only downside is that they may be quite costly, meaning about 6 euros per pair. The pedals' threads probably were damaged because there was not enough grease or good quality grease on them. This causes the two threaded parts joined together to have friction and day by day them getting destroyed.

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    The purpose of greasing threads is to get the right torque and to prevent the from corroding/seizing together, grease is often used instead of more specific antiseize compounds. Ungreased threads aren't going to destroy themselves, they'll just be a pain to get apart again. On the other hand, parts that are supposed to move (like bearings) DO need to be greased or they'll get damaged. – Jamie A Oct 28 '16 at 20:54
  • You are right. Hadn't thought about it... – user30058 Oct 28 '16 at 21:15
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    Titanium is physically weaker than steel. If used in a high load application, you do need to ensure the bolts can bear the load or they'll break. I don't think bolts wear when tightened, but the hex hole will wear if you repeatedly use them, and in that application, titanium will actually wear faster than steel. For one example, go to the Slowtwitch forum and search for the Tririg aero bolt skewer, which is a ti rod and had a hex hole. They changed this to T25 because of wear. Last, how are bolts relevant to the question? – Weiwen Ng Sep 22 '20 at 18:13
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    Pedals are not fixed using bolts. You would have to buy a pedal with a titanium spindle. Or some replacement titanium spindle like crankbrothers.com/products/titanium-spindle-kit (yes $150 just for the spindles and bearings). – Vladimir F Sep 22 '20 at 19:00

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