Can a 12-25 cogset be changed to 12-27 easily?

[goldfinch]

I have an 11-28 105 cassette on the rear (10 speed). That is another option to consider.

[emily_in_nc]

I have an 11-28 105 cassette on the rear (10 speed). That is another option to consider.

Yes, I actually misspoke above, goldfinch. The Ultegra 10 speed cassettes are 11-28 or 12-30.

I asked DH, and he does not have a cassette tool or chain whip here, so when I get a chance to take the bike in, I will likely just ask the shop for an estimate to do the work and provide the cassette. From the research I've done, if I have the medium-cage rear derailleur, I could use the 12-30, which I'd prefer as it would give me a 27 and 30t ring, two additional gears. This would be great when I'm riding in the middle chainring in front, which is most of the time. I hit that 25t cog far too early since I'm used to bikes with more easy gears and am a spinner, not a masher. I'd need my granny chainring a lot less with a 12-30 than with a 12-25. But I'll settle for an 11-28 if that's all that will work without a derailleur change. I looked at my derailleur, and comparing it to photos on ebay, I think it's gotta be at least a medium cage, if not a long. It looks much longer than the short-cage.

We shall see!