Originally Posted by
tyrion
Much easier and cheaper to just replace the 26t chainring with a 22t. Only costs $10 to $20.
It's quite possible, however, that the RD has a 22T capacity. The OP would need to swap out large ring as well.
Agree with above poster that you can purchase (a) replacement ring(s) for less than the cost if a 42 cassette, which, as with the chainring difference, may not work with the RD on the bike. Depending on which Deore RD, you may be limited to a 34T cog, which could probably be pushed to 36.
I toured with a Troll for a few years and liked it very much. I could climb walls with a 24-34.