What would be the speed advantage of the same rider on the same flat, paved course, on a road bike verses a mountain bike? Assume the MTB never spins out the gears.
I'm talking a standard, 20 lb. road bike with 90psi slicks vs. a standard, 25 lbs. XC hardtail with 40 psi knobbies and enough air pressure in the fork to keep it from bobbing.
Does the road bike, due to lower rolling resistance, lower rotational weight, and better aerodynamic position have a 5% advantage, assuming the same rider and no hills? 10%? 50%?
I just got dropped BADLY by my wife (a triathlete) on a flat bike-path ride of about 25 miles and am wondering if I should play the "my bike's an MTB, yours is a road bike" card to save my delicate ego.
(the fact is that she's in much better shape than I am, but I'd rather blame the bike )