I am having a problem with loose tightness of the Crankset (picture) and have no clue what type of tools do I need to deal with the problem. Any advice including the steps how to tighten it appreciated. Thanks in advance.

FSA Crankset

  • 1
    38-41Nm is the torque for the bolt and M17 a type of thread. So, you'll need a torque wrench to get the correct tightness. Focusing a little inside the bolt would help to see what kind wrench you need.
    – ojs
    Jul 3, 2021 at 13:05
  • Problem sorted @ojs -> see my comment on Swifty answer, but in short - 10 mm hex key does the job. I tried to find torque wrench to that spec and noticed that they are very expensive. Usually you get up to 15 Nm in affordable brackets of up to 30 USD. My guess is that 40 Nm means 'really tight' in subjective terms of my muscles (Athletic build) Jul 6, 2021 at 20:46

1 Answer 1


It appears to be a self-extracting crank, which means that there are two separate black pieces in there; the one that says LH and the one that says M17. The arrows show how they have different thread directions.

The 'LH' piece is the self extractor. It tightens left hand thread with a pin spanner, but as it hasn't shaken off it is probably tight so if you don't have that tool then don't stress it.

The centre piece with M17 and a right hand arrow is the bolt that actually holds the crank on, and has some kind of tool flats in that central hole, probably for a large hex key. Turn this clockwise with the appropriate size hex key (10 mm? +?) and torque up to spec (38-41 Nm).

The self extracting aspect means that if you turn this centre bolt anti-clockwise instead, it will pull the crank off.

Once tightened then monitor for loosening issues, if it loosens up again then something may be damaged.

  • I have bought 10 mm hex key and it indeed fit perfectly. Crankset tight. Thanks for your contribution Swifty. Jul 6, 2021 at 17:21
  • @PekotskiBit excellent, well done. You'll be able to recognise this kind of fitting in future too. remember to check it's still tight in 20 km or so
    – Swifty
    Jul 6, 2021 at 18:03

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