12-25 to 13-26 cassette Chain length

[Shoeman]

Currently running 12-25 cassette thinking of changing out to 13-26 because I don't use the 12t. Question is, will I be ok with the current chain or will I have change to a longer one. Thanks!

[Mark McM]

Almost certainly, the same chain length with work with either.

Consider: The chain only wraps half the sprocket, so for example, on a 12 tooth sprocket, the chain only wraps about 6, and on the 13 tooth sprocket the chain wraps about 6.5 teeth. So the difference in "ideal" chain length would be about 1/2 links. Since you can only change the chain length in 2 link increments, you really can't further fine tune the chain length for this small difference in sprocket sizes anyway.