Re: White Elephant
Short answer: Smaller wheels have greater rolling resistance, but they require less energy to accelerate.
Long answer: Imagine a polished metal wheel on a glass surface - no deformation. The actual area of contact is nearly zero, a point. The direction of movement of the wheel at this point of contact is tangential to the wheel and parallel to the ground, so the movement is in the direction that we want the vehicle to travel. This scenario is cleanly impossible, an ideal from a text book.
Now add deformation. A rubber pneumatic tyre. We need it for traction. Our perfect circle now has a flattened area on the bottom. The direction of the wheel's movement at the point the wheel meets the ground is no longer parallel to the ground. This results in road noise and heating of the tyre. Now, for the same area of tyre-road contact, a larger wheel will result in the motion of the wheel being closer to parallel to the road.
Acceleration: bigger wheels have more angular momentum, weight for weight, than smaller wheels. A child on a roundabout knows that if they starting spinning whilst hanging out, they spin much faster when they pull their mass in towards the centre of the roundabout. Effectivily they start as a big wheel, and become a small wheel of the same weight - in order to preserve the angular momentum the speed up. In reality, big wheels will also be heavier than small wheels because otherwise they would break more easily.
So, big wheels reduce the energy you waste in friction. If we had 100% efficient (you can never have 100% efficiency!) regenerative breaking in electric vehicles, the energy used to accelerate bigger heavier wheels wouldn't be wasted since it would be reclaimed when the vehicle decelerated - just as energy can be stored in flywheels.