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?
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".
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
I measured my 9/16" pedal threads at their outer diameter using a caliper, and got .561", which is darned near the decimal of 9/16".
