Originally Posted by
chinarider
Not going to happen. I mispoke before. My cassette is a 12-27. I may just go to a 12-23 or 12-25. I wonder how much difference there really is between 30x27 and 30x25 or 23. What do you guys think?
There is no practical difference between going from 12/27 to 12/25 for your purposes because all the cogs are the same except the last 2 cogs. The last 4 cogs on the 12/27 and 12/23 are different:
12/23 -- 12,13,14,15,16,17,18,19,21,23
12/27 -- 12,13,14,15,16,17,19,21,24,27
Note the 1T jumps that take you all the way except the last 2 cogs. With the 12/27, once you drop below the last 5 cogs, you have multitooth jumps. The difference would be nice but not super dramatic so I'd wait until the 12/27 wore out naturally before replacing.
Originally Posted by
NickDavid
If your LBS said "your chain is stretched" go to another shop. Chains do not stretch. They wear out.
I wouldn't ding them for this. Everyone knows they don't stretch, but this is just a colloquial expression that you'll hear all the time.