Originally Posted by
groovestew
Gearing I think is less relevant, isn't it? Unless you can spin out in top gear on your MTB, there's still a full range of gears. The differences between gears may be greater on a MTB cassette, so maybe there's a few seconds lost here and there with less smooth transitions, but I'm not sure that different gearing will make as much difference as tires, weight, posture, pedals, etc. I actually have road gears on my MTB now, and don't find they make me any faster. I just put them on so that the difference between gears is less jarring.
The gearing differences between my MTB and my road bike account for a lot of the speed difference for me. On my road bike, I have a close ratio cassette (12-24 9-speed, so it's something like 12-13-14-15-16-17-19-21-24), and on my MTB I have a wide ratio cassette (11-34 9-speed). The road bike has just the right gear for pretty much any speed I care to go, so I can keep my cadence in the mid-90s, or if I'm feeling feisty dial it into the upper 90s, and go whatever speed gives my legs the workload they're comfortable with. On the MTB, there are huge gaps between gears, and often I'll find myself going slower than I want because I can't spin fast enough in the gear I'm in to go the speed I'd like, and if I upshift I'm spinning too slowly to be comfortable. I end up hunting between gears, and eventually slowing down a bit to keep my cadence in my comfort zone.