Does weight really matter if you're not a racer?
02-12-09, 04:13 PM
#51
Bike ≠ Car ≠ Ped.
Also note that a lot of what is sold for bikes as "more aero" is only more aerodynamic if most of the air you're moving through comes from straight ahead or straight behind. In a place where it is common to have a steady 10mph breeze, and on a windy day it's 20mph with gusts up over 40mph... you're making a bet that you don't get much wind from the side. Even most racers can't move fast enough to minimize the effect of a direct side hit from a 40mph gust.
Supposedly, a lot of the aero testing done by manufacturers -- especially those of wheels, like Zipp or Reynolds -- focus on wind drag as it hits at an angle. They figure the same as you, that there's always going to be a bit of crosswind, and the bike direction plus the wind direction would result in an "apparent" wind vector.
A quick-n-dirty guesstimate would be: riding an easy 10 mph with a 10 mph crosswind from directly to the side, you'd have an apparent wind coming from 45 degrees to the side of dead ahead. Standing still would mean that the crosswind is coming straight from 90 degrees; doubling your speed to 20 mph would make the crosswind feel like it's coming from about 22 degrees away from dead ahead.
For more info, search the Road forum for threads about aero wheels (in particular, a claim from Zipp that their TT disc wheel "produces negative drag" under certain conditions).
