Originally Posted by
Zara Sp00k
hmmm, it sounds like even a 26, if I could find one, would be outsized, so then the question is, if I put on a 11-28 with an appropriate sized chain do you think it might be possible to use the 12-23 without changing the chain? Maybe I'd just not have to use the small chain ring when the 12-23 is installed.
If your derailleur has enough capacity to take up slack on an 11 28 cassette it will also have enough capacity to take up slack for the larger small cog on a 12 23 cassette
However, you may need a longer chain for the larger cassette. Going from 23 teeth to 28 teeth for your large rear cog will require at least one extra double link. Although you will be adding 5 teeth, keep in mind that the chain only engages halfway around the cog so you will be going from about 12 teeth engaged with the chain to 14-15 teeth engaged, a difference of only 2 to 3 teeth