I apologize in advance if I mix-up some lingo, I have almost no experience in fixing bicycle drivetrain.

Previously I had Comet CKM-7159 as crankset (I managed to find this datasheet that seem to describe it pretty good - datasheet)

Long story short, pedal track on the left crank got completely destroyed. Since it's a two-piece crankset (or I just have not enough muscles to detach left crank from the spindle) it looks like I need new crankset .

Based on my filters:

  • crankarm length from 170 to 175 mm
  • bottom bracket diameter - 24 mm
  • crank gearing - 1
  • chain gearing - 11

I get exactly 7 sets: Search results :(

I'm not trying to spend a fortune here, so I look at the cheapest option on the list: https://www.bike-components.de/en/Shimano/GRX-FC-RX600-1-Crankset-p72011/?o=200945-black-175-0-mm-40-tooth

It looks okay to my non-trained eye, I think it should work. However, when I look at the description of my bottom bracket, I see this interesting bit:

Only for cranksets without clamping screw on the left crank arm (NBD)

And as far as I understand my main candidate for new crankset actually has this clamping screw.

Do I interpret this correctly and this set is indeed incompatible with my bottom bracket? Or it will fit after all?

Also any other constructive criticism of my though process is very welcome, as I said in the beginning, I have almost no idea what I'm doing.

  • The compatibility notes don't mention your bottom bracket, so i assume it might be incompatible. Make sure your chain is long enough (it most likely is) to accomodate the bigger chainring. you need one more link.
    – Burki
    Sep 3, 2023 at 10:17

1 Answer 1


In many circumstances you'll run in to chainline problems or frame clearance problems if you replace a mountain crank like you have with a road/gravel one as proposed. You will not be able to use your existing FSA mountain BB with a Shimano road/gravel crank due to spindle length reasons. If you did use the GRX crank get a Shimano road BB for it.

Simplest and cheapest plan by far is get the left crank helicoiled, or talk to FSA and see if they can supply just the crank.

For the most part in actual practice, a 68/73mm FSA mountain 24mm BB can accept any 24mm mountain crank for 68/73mm shells.

  • Thank you very much, that is very clear and concrete advice.
    – kazaker
    Sep 4, 2023 at 9:06

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