I am a roadie who has figured out that "cross" bikes are pretty darn versatile. I plan on using my cross bike mostly for commuting and I have a question about the gearing on cross bikes. I have horrible knees and I run a 52-42-30 on my road bike (not sure if I'm running a 12-25 or 12-27 casette). If I understand correctly, cross bikes seem to run "in between" road bikes? I already noticed the earlier post on gearing, but to dive a little deeper, is a 46-38T with a 12-25 in the rear going to kill somebody who's used to the low gears? If so, will a 12-27 make much of a difference? Thanks in advance for any opinions on the issue!

Really depends on your commute route. If it's mostly flat and spinning, then stick with the tighter ratios of the 25. If it's hilly, then go for the 27. What you've got up front is pretty much set up for racing. But it should work fine for commuting as well. For group rides, you'd be undergeared though.

I am a roadie who has figured out that "cross" bikes are pretty darn versatile. I plan on using my cross bike mostly for commuting and I have a question about the gearing on cross bikes. I have horrible knees and I run a 52-42-30 on my road bike (not sure if I'm running a 12-25 or 12-27 casette). If I understand correctly, cross bikes seem to run "in between" road bikes? I already noticed the earlier post on gearing, but to dive a little deeper, is a 46-38T with a 12-25 in the rear going to kill somebody who's used to the low gears? If so, will a 12-27 make much of a difference? Thanks in advance for any opinions on the issue!

I'd suggest 48/38 with a 12-27. If you're just going to comute, go with a 50/38. Other options ...

1) Get a compact crank and get a 36 small chainring.

2) Get an XT rear mech and put on an 11-31 cassette.