switching cassettes
 

I'm switching cassettes and want to know if I will need to adjust chain length...

switching from a Ultegra 12-23 to a 105 12-27....other than a possible RD barrel adjustment will my current chain be okay with the switch??

thanks

Impossible to say without looking at it on the bike. In your big ring/big cog now, how much cage movement is left in your RD?

B-screw perhaps.

http://www.sheldonbrown.com/derailer....html#btension

always check your chain stretch--- old chain?- new chain? and do you know how to check the proper length on any given chain on any given bike?---- I'm sure that's been discussed on bf---

Since one is 9 speed and the other is 10 speed....
EDIT- I jumped too soon again:)

IF the chain was properly sized for the 23, you'll need to add a link set. Inner & outer link.
Going the other way, no problem, although technically, you would remove one link set. I probably wouldn't, just in case I wanted to switch back.