Determining MTB crank length

The stages PM price drop has me considering getting one. I can transfer it between MTBs as needed. What I can’t tell is the length of the cranks. I can tell you the SRAM serial number and date of manufacture. They are dec 2012 and June 2013 2x10. The road bike’s Rival has 172.5 stamped on it. But dang if I can find the info on the mtb ones.

Is there a place I am not seeing it?


It would be helpful if you posted pictures as well as the serial numbers. Even if we knew the precise models you were talking about, mountain bike cranks, just like any cranks, come in several lengths. Typically, MTB cranks might be longer. My MTB cranks are 175 mm whereas my road bike has 172.5 mm cranks.

Here are the pics. The newer is a SRAM GXP crank. I suspect the older is the same.

Both are 2x10 104 BCD.


Unless you ride a small frame, most likely your cranks are 175. Smaller frames sometimes get spec’d with 170s instead, but otherwise 175s tend to be the most common on MTBs. Maybe someone more knowledgeable than me can tell you something based on the serial numbers, but my guess is 175 unless you ride a small and then maybe 170.

Can you also post photos of the outside so that we can properly identify groupset and groupset generation?

In the first photo it looks to me that there is a 175 stamped just above the green number.




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Can you not measure them? They will be either 175 or 170, everything else is rare.