Changing a rear cassette...

maharg22

Hi All

I am due to receive a new bike in the next week or two and I am looking at changing the rear cassette.

Currently the bikes spec has Shimano 6800 11sp Ultergra and it comes with a stock 11-25T cassette, front rings are 50/34T FSA

Question is mainly what if any of the two options should I change to 11-28T or 11-32T? I know it's a personal choice, currently I have an 8sp Sora set up with a 11-32 on the rear and find that it suits me. However I am unsure of what the Ultegra is like.

Also will I need to replace the chain or is it just a simple case of swapping the cassette and that's it, job done?

Fairly new to home mechanics so please be gentle.

Regards

Ant

imposter2.0

Much depends on the rear mech. Short cage will probably only take a 28..

maharg22

Imposter wrote:

Much depends on the rear mech. Short cage will probably only take a 28..

Pretty sure its fitted with the medium cage.

arlowood

I'd just double check with the supplier that it is the medium cage otherwise as Imposter says you won't be able to fit an 11-32.

If it's a medium cage then with the 11-32 you will almost certainly need to to check that the current chain is long enough. With a 50/34 compact, the different chain length requirements between a 25 and 32 max rear sprocket is 1" (25mm) so you may be OK.

I've found this a useful tool for that purpose:-

http://www.epicidiot.com/sports/chain_l ... ulator.htm

wishitwasallflat

maharg22 wrote:

11-32 on the rear and find that it suits me. However I am unsure of what the Ultegra is like.

Also will I need to replace the chain or is it just a simple case of swapping the cassette and that's it, job done?

If 34 32 suits you as your lowest gear then th Ultegra lowest of 34 25 is very very much higher lowest gear and will require very much more torque for the same speed. If you prefer, or need, to spin a low gear (as I do myself protect my ropy old knees) stick with the 34 32. You will need a new chain if you do and a long enough rear mech.