Originally Posted by
tatfiend
From the book "Bicycling Science" rolling resistance is such a small part of the total resistance while riding that it has minimal effect. Air resistance is the big killer so far as bicycles are concerned as indicated by what pro riders do to optimize their time trialling position and components used.
At racing speed, yes. At touring or commute speed, no. Power lost to RR depends on speed, AR depends on the cube of speed. So they might go like:
6mph - RR 20W, AR 4W
12mph - RR 40W, AR 32W
24mph - RR 80W, AR 256W
It's also damn hard to get more than minute aero improvements, but racing tyres of the same width vary by about 40% in RR. Changing tyres is one of the cheapest performance boosts that you can make to a bike - the effect can equal thousands of dollars spent on carbon fibre.
And
most of the time in a road race most riders are drafting anyway, which reduces the importance of AR, but not RR.