Hi,

Tech. question here. My Trek Pilot currently has a 12-25 cassette (10 speed) in back with Ultegra derailleur. It's a triple in front (I think it's 30/42/52 but haven't actually counted). In lieu of springing for a new road bike right now, I would really like to change out the cassette for a 12-28, which I assume would be pretty easy. However, I'd love to go even lower (12-30) if my derailleur could handle it. I'm pretty sure it's a medium cage simply because the bike has a triple crank (and from its appearance).

What's the upper limit on what rear cassette I can put on with my current setup without having to go to a long-cage derailleur?

Thanks very much in advance!