Changing rings on cassette

[derrick]

Have a campagnola 10 speed rear cassette with a 12 tooth small cog, can it be changed for an 11 tooth or do i have to change the whole cassette. if it's possible i would loose the largest ring.
Cheers Del.

 

[Tollers]

It would work, but shift badly for the highest gears as the shifting ramps are in different places. I tried something similar before giving up and using the original cassette gearing.

Tollers

 

[accountantpete]

You would also need an 11t lockring.