Originally Posted by
DieselDan
Right on the money Leebo. The OP failed to recognize the wheels itself as a gear. MTBs usually cannot get close the same gear as a road bike, even the 29"(622mm rim) wheels, as the frame of an MTB may restrict the chainring to 48 teeth.
Nah, I don't buy it. But, I also don't count downhill speeds as an indicator of pedaling efficiency, either.
If a rider takes a MTB, puts it on the big ring and small cog, and can spin his legs well past 100-120 rpm on flat ground to get near 30 mph,
then he's maxing out the possible human-powered speed of the bike-and-rider combination. IMO, that's the point where taller gearing makes a difference -- not in efficiency, but in top speed capability.
Use the equivalent ratio on a road bike, and it'll be easier for the rider to spin the same cadence and/or maintain the same speed. That's a certain indicator of efficiency.
26" vs. 700c wheel diameters don't matter as much as people seem to think, either. At least not when big, fat MTB tires are being used -- my MTB's 2.whatever" tires are nearly as tall as my road bike's 23mm tires.