Will 12/27 make much of a difference?

It depends on the steepness you're going to and the state of fitness you have.

Thanks for the reply. I am in pretty good shape. I put in about 40 - 80 miles a week (depending on running/swimming schedule) with a weekly average of about 20 - 21 mph. As far as steepness goes ... I don't know any of the grade's %tages. I do know that the area is known as the Alps of Texas and is supposed to be a tough ride. (Texas standards anyway)

I rode a 12/25 in and around the Atlanta area (pretty rolling terrain, some steep stuff, but not very long at all, I'd say everything under 1 mile), but when I first went into the mountains a little farther north of here (not much steeper, but much longer climbs, up to 8 miles, I used a 12/27. The bailout gear came in handy a few times as I tried to haul my carcass around a few of the switchbacks on Wolfpen. I'd say that if you hardly ever use your 39-25 now, but you think you might need a bailout, the 12/27 will work just fine. The cassette is hardly different at all, except for the last 2 cogs--a 24 and a 27.

I have the same 53/39 cranks but use a 12/27 cogs. I use the last two (24 and 27) as my bailout insurance in case the terrain goes very steep.

I appreciate all the input. Sounds like it will be worth the money ... just in case. Thanks much.

LAV25 said:

I appreciate all the input. Sounds like it will be worth the money ... just in case. Thanks much.

I am either going up or going down here in the mountains. I went from a 11/21 to a 12/27 a while back and I am very happy with it.

LAV25 said:

I appreciate all the input. Sounds like it will be worth the money ... just in case. Thanks much.

One quick note, rear derailleurs come with different cage lengths. Short cage deraillers (specifically Campy) list a maximum gear of 26t. I'm pretty sure a 27 will still work, but it's not recommended by the manufacturer. Just and FYI...