Recently I tried to unscrew the left pedal of a bicycle by turning it counter-clockwise with a spanner lengthened with a piece of pipe. The net result is the spanner broke apart and the pedal is still there.

This makes me wonder.

Is that just threaded joint or is there something else besides threading? Is the threading left-handed or right handed? Do I need anything else except what I would normally use to unscrew a threaded joint?

  • 3
    No doubt there's an exception on some bike somewhere, but on 99.99% of bikes in the world the left-hand pedal is threaded in with left-hand threads and the right-hand pedal is threaded in with right-hand threads. Jul 30, 2012 at 12:06
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    I was really miffed, when my dad and I did the same thing to a Mastercraft wrench, which has a lifetime warranty, and we were looking forward to returning it, but then someone stole the set out of his car. We did the same thing, attached a pipe to wrench, bounced up and down... Amazing how strongly it can be bonded over time.
    – geoffc
    Jul 31, 2012 at 2:46
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    There is a great post on here about how to remember which way the pedals are threaded bicycles.stackexchange.com/q/3957/213
    – Gary.Ray
    Aug 1, 2012 at 18:44

3 Answers 3


Like Daniel Hicks says, they are threaded opposite to each other. This ensures the act of you pedaling is constantly tightening them both. If they were both the usual right hand threads then the left pedal would eventually unscrew and fall off.

So, if you're like me and use the right hand rule to constantly assess which direction you should be turning things to make them move in the direction you want, you'll now need to switch to the "left hand rule" for the left hand pedal.


About "just threaded" vs "something else", the answer is: they are just threaded.

A possible problem, though, is rust or other chemical bonding, which might make significantly difficult to take the pedal off with raw force (a friend of mine recently broke a spanner, even applying the force in the correct direction).

As for the right vs. left rule, if you attach the spanner with the handle pointing upwards, you have to pull the handle to the back of the bike.

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    Can it be said that you always rotate the spanner against the forward rotation of the corresponding crankarm? (I always forget these mnemonics, it takes me sooooo long before I need to unscrew a pedal again...)
    – Jahaziel
    Jul 30, 2012 at 16:28
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    @Jahaziel To losen the pedals, yes. Besides that, best mnemonic: In a scene from the movie "Breaking Away", the pseudo-italian boy TIGHTENS the pedal by just grabbing the pedal with the spanner and than back-pedalling it (the freewheel makes it possible, rear wheel doesn't spin). When you ASSEMBLE the pedals, it is the quickest way to tighten them (backpedaling while grabbing the spanner), even with the bike standing on its wheels. Jul 30, 2012 at 17:04

Pedals are threaded as said above, but over time the pedal may become stuck, especially when the pedal is made of steel and the crank is made of aluminium.

Before trying to unscrew it, you should spray some degreasant here, like WD-40. Wait for a couple of minutes and then try to unscrew. You should also use a proper pedal wrench instead of a standard wrench (easier and more force is applied). If it doesn't work, spray more degreasant, wait more, and try again. Sometimes spraying degreasant and waiting a whole day (or night) is sufficient to unscrew it, sometimes it just doesn't move, and my advice would be to just change the crank and the pedal, or else you might end by hurting yourself.

That's the recipe I used for many old bikes, and it usually works but sometimes, even if the bike isn't rusted, there's no other option than to dispose of the crank.

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