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

[Triskeliongirl]

Hi emily. Its trivial, but you do need to swap out the entire cassette. If you have a RD than can handle a 12-25 I would be very surprised if it can't handle a 12-27. You can do it yourself very easily, I do it all the time (but u do need a special tool and a chain whip). But yes, you probably do need either a longer chain, or to put back in a few links that you probably removed when the chain was first installed. This too you can do yourself. Depending on what RD you have, you could possibly accomadate a 12-28, which if the 25 is giving your trouble is probably worthwhile. If you need to change the RD, you could install a mountain RD and then use an 11/34 like on your friday. This is what i have with a compact double on my travel bike, and a 12/27 on my racing bike. I am surprised the trek pilot fits you. I would have thought it had too steep a seat tube angle for your body if I remember correctly (don't you have proportionally long femurs?). I ride a cervelo RS 48cm now w 650c wheels, which fits me like a dream (my racing bike). My terry isis 19" I had converted to a travel bike with s/s couplers and that works great too. My 17.5" terry isis was really too small for me and is now being ridden by my son's girlfriend.