Larger rear cassette

datpat64

I'm looking to change my rear Shimano Casstte from 11-24 to 11-28 (help out on the hills round here) !

there's a couplle of things i need to find out ;

1. SRAM cassette will be OK for this as I can't find Shimano at 28 ?
2. DO I need a different rear derailleur (long casge as opposed to short) or can I get away with a slightly longer chain length

The new cassette is quite a bit bigger than the old one and I the chain is to otight round the jockey wheels if i simply use the same set up and just change the cassette.

Thanks

Dave

jibberjim

Yes SRAM will be fine - surprised you can't find a shimano one though

http://www.rosebikes.co.uk/article/shim ... aid:443959 for 30 quid?

http://www.rosebikes.co.uk/article/shim ... aid:366574 for 40 quid?

http://www.rosebikes.co.uk/article/shim ... aid:286215 for 130 quid?

You may well need to lengthen your chain, your derailleur will be fine though.

Berk Bonebonce

Are you using a compact chainset already?

Erudin

When I changed the double to a triple on my Bianchi I also fitted an 11-28 cassette. Needed a longer chain and triple mechs (long cage rear). Also run 11-28 or 11-32 9spd mtb cassette on my winter/audax/tourer bike using a Shimano M530 Deore rear mech (45t capacity so will take up chain slack even with 52/42/30 triple, 34-11 cassette). Make sure the chain can get into big/big to be safe.

If you look at the tech docs for a mech it will give the "capacity", for rear mechs, the capacity (on a rear mech) relates to the amount of chain slack the derailer can take up, and is equal to the front range plus the rear range (see sheldon link below). You might get away with your current mech (probably 33t capacity) or a medium cage rear mech (about 39t capacity).

Chain length calculating:



ParkTools has an equation method:

http://www.parktool.com/blog/repair-help/chain-length-sizing

See also:

Javascript Bicycle Chain Length Calculator ("rigorous equation")

Sheldon: Capacity (of a derailer)

datpat64

Guys ! As always many thanks. Looks like the derailleur is fine just need to add some chain length.

Thanks for taking the time to reply with such easy to follow answers

Thanks