My Deore FD-M590 is missing the instructions how it should be mounted and I would guess like any front derailleur, however what confuses me is little pink (my eyes) insert/plug which I don't know what to do with it.


What is the purpose of this thing?

  • 1
    I think it might be to keep the mech in the highest gear without needing the cable so you can line the red sticker up with the chainring teeth to get it in the right position when clamping to the seat-tube.
    – chored
    Commented Jan 27, 2019 at 14:32

1 Answer 1


You can search Shimano's Technical Documents site for manuals.

Here's the manual for the M590 BB, crank and front derailleur: https://si.shimano.com/pdfs/si/SI-6SA0A-001-ENG.pdf

The red insert is apparently a 'Pro-Set Alignment Block' and is there to help set the height of the cage above the large chainring.

  • Many thanks for providing the link as well, I was unaware of this site. Commented Jan 27, 2019 at 15:50
  • 2
    Surprisingly many people don't seem to be aware of the Shimano Tech site. Commented Jan 27, 2019 at 15:54
  • @ArgentiApparatus: And unless you buy OEM stuff, the packaged Shimano items always come with the same user instructions sheet that you find on their PDF manuals page.
    – Carel
    Commented Jan 27, 2019 at 22:00

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