tahoeeddie

i have a road bike, 10 speed cassette 11-25 currently. and i'm thinking about putting in an 11-28. do you know if i need to add links to my chain?

it's a new chain (a couple of months), and the chain was measured off of the 25.
i don't know how much the RD can adjust for putting in a 28.

thanks.

HillRider

The rear derailleur doesn't define the required chain length. Shift the bike to big-big (large chainring and largest cog) and see if there is any slack and if you can fold the chain over itself at least 4 pins. If so the old chain should clear the newer cassette. If the chain is now the minimal length to just allow big-big with the 25, you need 2 more half links (1" additional length) to clear the 28T.

tahoeeddie

Thanks.i ended up just being able to slap the 11-28 on. some slight adjustment to the b-limit and it's all good to go.

fietsbob

bear in mind the RD strain if you cross chain Big-Big things may stretch too hard .

like the chain is a bit short .. you can get it, forced , to upshift.. but wont come back down under return spring pressure..

but if you shift to the small ring first, consistently, you might get away with it ..


Might be a good time to put a new chain on with the new cassette, anyhow..

FBinNY 

How the heck would I know?

But you have the bike and can easily find out for yourself.

Every 2 teeth added to either of the big (bigger, biggest) sprockets calls for 1/2" of additional chain. So adding 3 teeth means you need 1" more chain, which turns out to be the least you can add.

Now you know you need 1" more chain, but that doesn't mean you need to lengthen because the chain may already be long enough. So shift to big/big and see how much chain you have to spare. Pull the lower loop forward at the bottom of the chainring, and note how much you can pull up.

The minimum is just shy of 1" and you need 3/4" more so If you can pull up almost 2", you're in. If you can only pull up 1" or so, you don't have any to spare and will need to lengthen.