Originally Posted by cplager;16120983...
A couple important points here:
1) When accelerating a bicycle, you need to not only accelerate the wheels (both linear and rotational sense), but also accelerate the bicycle and the rider. If you compare the mass of the wheels to that of the bike and the rider, you'll see that the wheels are are very small part of a bigger picture. So, yes, it takes more force to accelerate a heavy tire than a light tire, but not (relatively speaking) a lot more force to accelerate a rider, bike, and a [I
"heavy"[/I] tire compared to the same rider, the same bike, and a "light" tire.
2) When you are moving at a constant speed, you only need to provide enough power to overcome the frictional forces against you. It will take less energy to keep a heavy but low rolling resistance tire moving than a light but high rolling resistance tire.
That's how I see it also. Going uphill at a steady or declining speed it's basically just the extra weight.
But going downhill, say coasting down, there are a couple of things going on. We're accelerating at least at first, and the angular momentum will slow that slightly. Very slightly. Then the angular momentum and extra weight will allow a higher speed I think depending on the grade. At the bottom our heavier tires will hold the speed better, again because of the rotating momentum.
So tally it up: uphill steady, slowed by just the extra weight. Downhill, helped by extra weight AND angular momentum. Flat after, helped by angular momentum, slowed a tiny amount by extra weight. Going
back uphill and slowing,
helped by the angular momentum and held back by weight. I'm not so sure that it wouldn't be
advantageous to have a heavier tire on some type of rolling course.