Over-inflating tires increases rolling resistance on road surfaces. This happens because the higher the tire pressure, the less the tires are able to absorb the force generated from riding over irregularities in the road.

So why are *stiff* frames so important? I'd think that the further up the vehicle (bicycle and rider) this energy must travel the more it would increase rolling resistance (in much the same way as over-inflated tires). For most every application except out-of-the-saddle sprinting, wouldn't a less stiff frame result in a faster ride?

I'm assuming that the only time an overly-stiff frame would be an advantage is when you're putting out a ton of watts (at least enough to generate frame flex sufficient to rob significant wattage from reaching the road). My guess is that this might start somewhere around 350-400 watts - something very few cyclist, especially triathletes - put out for more than a few minutes or in a sprint.

Just wondering.