The FC-M171 and FC-M171-A are listed separately in Shimano's spec sheet (p73-74), but I can't see any difference between the listed specifications. Curious, as my old crankset was FC-M171 and the replacement that I've just fitted is labelled FC-M171-A. It's not the crank arm length.

  • Can you see any difference between them? country of origin?
    – Noise
    Nov 19, 2021 at 20:27

1 Answer 1


I believe the A is a different tooth count. The normal one is 42-32-24T, and the A model is 48-38-28T.

Image from their 2017 dealer support manual.

enter image description here

  • 1
    Thanks, but the spec (and the screenshot) show both the "A" and "non-A" are available in 48-38-28 (while the non-A is also available in 42-34-24). So it's not as simple as just different tooth count, unfortunately!
    – matthewr
    Nov 19, 2021 at 20:19
  • 2
    Hmmm true, i'll dig deeper and amend my answer when I find one.
    – Nate W
    Nov 19, 2021 at 22:46
  • 1
    Looking at the exploded views (EV) of both FC-M171 & M171A, the chain guards are different part numbers and look slightly different. On the EV for 171A it has an interchangeability table of parts with M171 and it notes the chain guards are a "B" fit which means they can be interchanged but look different.
    – Jeff
    Nov 21, 2021 at 3:43
  • @Jeff thanks, just seen this. Sounds like that's right - I'd mark it as solved if it was an answer instead of a comment!
    – matthewr
    Nov 25, 2021 at 18:52

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