So I got the 2009 Trek XO2 working with my old gear from the Salsa. I am still uncertain about keeping the Campy Chorus Carbon 10 levers, I mean I like them well enough, but as it stands I don’t see myself converting to a Campy drivetrain and if I upgrade to 10 speed I’d rather go SRAM or Shimano. And currently the 2009 SRAM Rival group looks like the best deal going. The only question that remains is one of gearing. I’m not hoping to make this bike a full time ‘cross racer, more of a light off road touring & dirt buddy if you will, so even in that context carbon shifters seem like a bad idea. I know, I know, bar-end shifters and aero brake levers are always an option. But so are flatbars and a set of cheap SRAM gripshifts.
The real crux of the build, besides which shifters to go with, is just how compact of a chainset I want. Alex Wetmore has a great page talking about the pros and cons of 110 vs 94 BCD cranksets and how compact doubles, especially when you go with something like 46/32 or a 44/31, can actually give you more reasonable chain crossover. When I was looking at gearing tables for 2 x 9 mountain bikes, I pretty much came to the same conclusion. It seems most 2 x 9 mountain drive trains run something like 44 x 29 up front and an 11-34 in the back. Some racers will bump that front chainring to a 46 I guess (or down to a 42) depending on the speed of the course. A 44 x 11 gear gives 104 inches development and a 29 x 34 gives 22 inches (on 26 x 2.1″ tires w/ 175mm cranks). I mean that’s a pretty good spread for off road I’d think.
SO, I’m leaning towards using the more common 110 BCD crankset with a 46/34 up front, unless I happen to win a set of sweet 8 year old Race Face square taper Turbine cranks in a 94 BCD double configuration (or vintage Ritchey Logics) I would say that the advantage of something like a 44/31 setup using an 11-28 cogset gives almost the same range. On my Jake the Snake when we rode across the US I ran a 50/40/30 triple with a 12-32 8 speed cassette in the back and Rivendell “Silver” friction barend shifters. That worked fine. I didn’t find myself fully loaded in 1st gear very often. I’d say I spent most of my time on that trip in the middle 40 tooth ring switching between 24 to 12 on the back (45-90″ development). And as I recall, the real problem was when I shifted up to the 50 tooth ring I really only got two more gears using 50×14 and 50×12 (96″ and 112″ respectively). We generally didn’t go over 18 mph, and as I recall there were only a couple of days when I remember us using having a tailwind and actually using those big rings.
And when Hanka and Katie battled it out for 1st at Pijnacker this past weekend? Well sadly the Rainbow Colors didn’t win it on SRAM Double Tap technology, but it was a good battle nonetheless.