I am interested in getting a left-side power meter for my road bike. It has Shimano 105 components. I'm considering a 4iiii Precision left-side crank, in a 105 or Ultegra version.

I looked, and don't see the size of my current cranks marked anywhere. How do I measure them? Is the distance the total length of the crank, or the center-to-center distance from the bottom bracket to the pedal spindle?

1 Answer 1


It's the center-center distance, but it should be stamped on the inside of the arm.

  • Adam, thanks for the reply. Will it be stamped on the inside of both arms, or just one? And where on the inside, exactly? I looked and didn't see it. (I have a Wahoo cadence sensor on the inside of the left arm. It's possible it's covering the stamp.)
    – Duncan C
    Commented Jan 1, 2022 at 2:19
  • 1
    Ah-ha! I went back and looked more closely and found it. It seems my cranks are 172.5 mm. Thank you!
    – Duncan C
    Commented Jan 1, 2022 at 2:25
  • For others' reference, here's another question that shows where the length is stamped. bicycles.stackexchange.com/questions/67619/…
    – Weiwen Ng
    Commented Jan 2, 2022 at 14:46
  • Thanks for the answer. I did eventually find the crank length info printed on the crank.
    – Duncan C
    Commented May 7, 2022 at 23:50

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