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I have a bike with a 36t chain ring. I’m changing it to a 28t. That’s 8 teeth difference. The derailleur is a Deore M6000 GS.

How much should I shorten the chain assuming the chain is currently the correct size for 36t?

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    Install the chain and measure the slack. Aug 16, 2021 at 0:37
  • Fullsus or hardtail?
    – Lucero79
    Aug 16, 2021 at 14:40

1 Answer 1

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I'd guess that four links need to be removed.

A 36T chainring has 18 teeth in a half-circle where the chain is engaged.
A 28T chainring has 14 teeth in a half-circle where the chain is engaged.

A difference of 4 links (four half links, two full inner/outer pairs)

However that presumes that the chain was the right length to begin with, and that the changed angle between upper and lower run of chain are close enough (they probably are)

I'd start by putting the chain on big-big, through the derailleur, and simply holding it closed. As long as you don't run out of chain when in this gear combo, you're above the minimum. Visually check the rear mech - if it looks painfully straightened, it might need another link or two.

Then join the chain. Check that the smallest rear cog does not cause the chain to rub on itself when in the smallest chainring. If it does, remember to avoid that gear combination.

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    Thank you! Helpful advice. Logic makes sense and I didn’t realize only half the chain ring is engaged at one time only.
    – Listerone
    Aug 16, 2021 at 17:43

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