Tuesday, August 3, 2010

Schlumpf Comparison

As we approach the end of the year, I'm getting closer to purchasing something from Schlumpf. I've been going back and forth between the Mountain Drive and the High Speed Drive (HSD).

Compared to my current setup, the Mt. Drive gives me 4 lower gears and 2 higher gears.

The gear chart here shows the benefit of gaining a huge number of lower gears by adapting the Mountain Drive . I've included the center column to compare the drive's specs with my current setup. I'd be getting 4 lower gears, 2.2, 19.0, 16.7, 11.8 gear inches. Unlike the HSD that's limited to one of two chain ring sizes, the Mt. Drive lets owners select any size chain ring.

Although the Schlumpf drives are easy to engage, I would rather not go through the motion of engaging it from normal stop and go rides along flat or downhill rides. Ideally, the effective 20T chain ring will be used strictly for hill climbing. I plan to spend most of my time in the larger chain ring.

Of all the chain ring sizes to choose from, how do I pick? Easy. Being that I typically start from a full stop in gear 3 or 38.1GI's, I've chosen a 50T chain ring to bring this down as my first gear in the largest chain ring. 41.7GI's is fairly close to 38.1GI's. Sometimes I start in gear 4, so I will be able to start with the Mt. Drive disengaged using the large chain ring from a start as long as I'm between 38.1-44.4GI's. 41.7GI's.

Compared to my current setup, the HSD gives me 2 lower gears and 4 higher gears.

The HSD Gear Chart here shows that 2 higher gears and gained and 1 lower gear is lost by comparison. By choosing the HSD, I'll have 15.9GI's as my lowest gear as opposed to 11.8GI's from the Mt. Drive.

I find myself spinning out at my highest 72.7GI. Will I ever really get a chance to use something as high as 120GI's? How steep of a slope would I have to be going down to utilize that effectively and would it be worth the expense of not getting the ultra low gears that the Mt. Drive offers?

Ashley from Utah Trikes recommends 18-130 as an ideal gear inch range. He seems to be the speed demon type claiming 45mph regularly on downhills. Neither of these setups brings me to those numbers, but the HSD definitely brings it closer than the Mt. Drive would. Fellow BROL members have mentioned that their ideal top end would exceed 100GI's and sometimes as high as 120GI's.


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