Originally Posted by
cplager
(1) Smaller tires have more rolling resistance. Just like thinner tires do. It's a real effect. But it's not overwhelming. (World's fastest bicycle has 406 tires).
2) Smaller tires are going to have less aerodynamic drag than big tires. But effect of that will depend on rims and will likely be dwarfed by rider's aerodynamics.
3) Narrower tires have less aerodynamic drag and more rolling resistance. So it isn't a simple one is faster/slower than the other. These effects are smaller than other aerodynamic effects.
4) In a pelaton, yes, I believe a Bike Friday rider would do better than a rider on 700c wheels because she would be able to get closer to the rider in front of her. The aerodynamic benefit of this will outweigh the (real) deficit caused by rolling resistance increase. Yes, the UCI made this illegal in races.
5) As far as smaller wheels having faster acceleration, yes, there is a real effect. No, it's really a small effect.
6) I'm assuming the Prius has small tires so the car can be made smaller. If you put bigger tires on it, you'd need to make the car bigger and therefore heavier and less aerodynamic.
There has been very little valid testing of bike, tire, wheel rolling resistance.
The recent change to wider tires and complete changing of the tire design from real world testing is why I question many of the assumptions.
The bicycle industry assumptions I have just recently seen proven false--Narrower tires are faster---higher pressure tires are faster----suspension forks are slower---higher thread count gives less rolling resistance---
give me pause to question what many people see as absolute givens like ---smaller wheels have more rolling resistance (I believe this is true but I haven't seen proof).
Your statement number (6) ---- overall size is critical and keeping the vehicle components small but I think smaller wheels take less energy to get to a given speed. The reason this comes into question for me is they are smaller than Corolla wheels. I do know also Toyota was attempting to get the Prius to the lowest possible wind drag so you may be right, I may be wrong.
Sometimes physics does not work in the same relationships that we think it should.
The historical testing of bicycle tires on a smooth drum (which was industry standard as recently as 2011) shows how little testing is really done.