cccorlew

Just how freely can I change sprockets on an Ultegra 10-speed cassette?
I have a 11-23 I'd like to
toss out the 11 and 12
get a 12 that goes in position 1
add a 25 on top

Shimano makes this configuration, but rather than buy it, can I just add those two sprockets?

Or
make a 13-25 (again, Shimano makes this configuration) buy getting a 13- tooth 1st position, adding in an 18 and adding a 25 on top?

I guess I'm asking, do all the sprockets come apart, or are some stuck together. If they are stuck together, how can I find which ones are? Is there a set of rules somewhere?

Proximo

The three largest cogs are mounted to a common carrier so you'll have to replace them all at once.

Sheldon Brown

Actually, the 25 would have to go on the bottom! ;-)

Unfortunately, it won't, 'cause the bottom sprocket needs to have a recess to fit over the hub.

This approach worked great with 7-, 8- & 9-speed systems, but not with 10-speed.

Generally with Ultegra the 3 biggest sprockets are on a spider unit. Other ones are sometimes rivetted in pairs, but can often be separated. The smaller ones are always separate.

Sheldon "Custom Cassettes" Brown

cccorlew

Thanks for the help. Does this then add up to: "You just have to buy a new 12-26 cassette and there is no way to recycle most your 11-23 so you can save a few bucks" ??

And, just for educational purposes, are you saying that my 23 tooth sprocket has a recess and is different than a 23 tooth that's justy inside a 26 tooth?

cccorlew

Whoops. I think I found some info at
https://cycle.shimano-eu.com/media/te...9830608752.pdf
that helps me understand all this weirdness...