Switching from 12/ 25 to 12 /27 cassette

[Chuck Hammer]

I will be changing my cassette soon and wanted to know if I should add a link to the chain when I do..... thanks!

[AngryScientist]

generally you shouldnt have to. depends on how you sized the chain in the first place. it's really only a potential issue in the big-big combination, which you probably dont use much anyway. best to put the new cassette on, and see how stretched out the rd is in the big-big combo.

[redir]

I doubt it but maybe, just depends on if when you set up your 25 you were on the low side. You'll just have to give it a try. Once set up for the 27 though you will be able to use any cassette.

[Chuck Hammer]

I set it up in the big/big with the RD pulleys at 90 degrees. Guess I will have to swop it out and see how it runs then.
Thanks

[Ken Robb]

I made this swap on an Ultegra 9speed triple without adding to the chain.

[WillT.]

I made the exact same switch not too long ago and I didn't have to lengthen my chain. I determine the length of my chain by making sure that it doesn't rub the derailleur cage when in the small-small position.

[David Kirk]

You may or may not have to but my question would be - how many miles on that chain and is this new larger cassette new?

I would just be concerned with an older used chain on a new cassette.

dave

[norcalbiker]

We just did a swap from 25 to 28 and it was fine.

[yakstone]

I am with DK on this one. I change both the chain and casette together.
NO sense running an older chain on a new set of gears.

[Chuck Hammer]

Everything is DA 7900 and the chain can't have more than 500 miles on it plus the cassette is new one. Very good point one would think I'd be OK?

[John M]

I set it up in the big/big with the RD pulleys at 90 degrees. Guess I will have to swop it out and see how it runs then.
Thanks

It should work fine, especially if you don't actually use the 53/27

[rounder]

I have 12-25 on one bike and 12-27 on another. I know it depends on where you ride. But for me, both bikes ride about the same. i am in hilly country.