What do you guys think is the best cassette gear ratio for a hilly course (IMWI)?
The climbs aren't so dramatic you'd ever need the 28; the downhills aren't long enough; the flats aren't flat enough; and it's not windy enough for a tailwind to necessitate an 11 (or conversely, I doubt you'd bottom out a 12). The course seems like 100 X 70' climbs. Up. Down. Up. Down. Technical turn. Up. Down. Actually, I think making 101% sure your derailleur cables are in perfect working over because your front derailleur will get a workout.
IM Moo '04
11-28. 12-27 or 28 might be better to gain another middle cog. I think you'd have to be a reasonably strong climber to get through with a 12-25 and still have the freshest possible legs for the run. Spinning up those hills while others are grinding is a good thing. I don't think a 12 vs 11 small cog makes very much of a difference for the downhills on that course. They are either so steep that the fastest option is to tuck and bomb, or so short that there is minimal time spent spinning in the biggest gear combo, or they have a turn right at the bottom so you are bleeding speed to make it around the corner in one piece.
My best IMOO bike was 5:49 and I used a 12-25, but that was also with a 50/36 compact crank.
EDIT: I should add that I am a spinner by nature (95+ cadence in sprints, gun for 90 in HIMs and IMs). I also really prefer a very tight range of middle gears, hence the compact.
My only options are the two I mentioned. I'm going with an Ultegra cassette, and those are the biggest offered on Pricepoint and Jensonusa. I am currently running a 12-23, but am not 100% what I'm running on the front.
And yes, I will be double checking all my cables, and probably replacing them prior to the race. Last thing I need is for them to snap on me.
haven't check the avg. grades for IMWI, but I believe the hills are not too steep (less than 5% grade). If, so the 12-25 should be fine. I've climbed up to a 9% grade with a 12-25 and survived. Anything over 10% grade and you definitely want the 11-28.
[quote=PJT]They are either so steep that the fastest option is to tuck and bomb, or so short that there is minimal time spent spinning in the biggest gear combo, or they have a turn right at the bottom so you are bleeding speed to make it around the corner in one piece. [/quote]
This is an accurate description. They're short climbs, maybe 50 rotations of the crank and you're up. But the downside is just as short before you're back to the small chain ring and spinning again. I think I read somewhere how to climb little rollers like this: Just before you reach apex, maybe 10m to go with just a few turn-overs left, go ahead and shift to a bigger gear, push through the last couple of cranks up-and-over, and you'll already be in gear the instant that gravity takes over. And I do recall more than a few technical turns at the bottom of a lively descent. You'll notice a few hay bales at the bottom of some turns, so not all descents are balls-out.