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How do you measure pedal axle/spindle size?

Replacement pedals and accessories specify a size like 9/16" or 1/2". How do I measure my current pedal to see what I need? Is it just a matter of putting the pedal threads in a caliper and measuring the outer diameter of the threads across the axle/spindle? Or do you need to measure the solid part, excluding the threads?

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They're standardized between different types of cranksets.

One piece cranksets use 1/2" x 20 tpi. Three piece cranksets (most bikes) use 9/16" x 20 tpi. Old French things use something else, but these are rare (and instead of being marked with R and L for which pedal is which on the spindle, it will be D and G).

If you want, you can measure it like any other bolt. Or, take the pedals to a bike shop and compare them to another pedal.

You find one piece cranksets on some BSO's (i.e. bikes you get from places like Walmart), children's bikes and very old American bikes. Otherwise, you should have a 3 piece crankset and use a 9/16".

  • I measured outer thread diameter as 9/16" pursuant to your Bolt Depot link since I'm not sure what kind of crankset I have, I haven't gotten to that yet. Based on your categories it could be either, so I just measured it. Thanks. – compton Aug 22 '16 at 19:58
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    If you post which bike it is (or look at the crankset -- theres a picture of a one piece crankset at the link), we can tell you. – Batman Aug 22 '16 at 20:09
  • Thanks @Batman. I see from one of your links that it is a three-piece crank. (As for the kind of bike I have, I've been trying not to out myself, but it's a department store bike. When I start asking about my front fork, maybe tomorrow or the next day, I'll be totally giving myself up as owner of a BSO.) – compton Aug 22 '16 at 23:17
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    @compton Gotta start somewhere! Nothing wrong with department store bikes if it works for you. Many times they lead to the purchase of a real bike! :P – Nate W Aug 22 '16 at 23:32
  • In most parts of the US, the only affordable bikes for most people are BSO's. Not the end of the world to own one (I only got a non-BSO when I started grad school, because the campus had a decent number of old decent bikes around). – Batman Aug 31 '16 at 15:56
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for the most part, if you can identify your cranks as 1 piece of continuous metal, they are 1/2", and in most other cases they are 9/16" unless they came with/require a proprietary pedal spindle system

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