Originally Posted by
subgrade
One other thing which I don't see mentioned often (if at all) by the proponents of wider tires at lower pressures for smoothing out the ride: if you run the tires at pressures low enough to substitute for a short travel suspension fork, you get lots of rolling resistance on smooth, hard pavement (worth 1-2kph). And that resistance is there all the time, unless you get off and change the tire pressure each time the riding surface changes.
Not totally true - bike tires aren't like car tires and the energy spent in deforming the casing is pretty minimal and is far outweighed by the vibration dampening improvements which improve efficiency. The wider the tire, the less energy wasted because, at lower pressures, the contact patch is wide but not very long compared to a narrow tire at the same pressure. In other words, the wider the tire, the longer in it's rotation it can stay "round"