Originally Posted by dafydd
i'm no physical therapist or psychologist, but i tend to feel rolling around on two beanbags is going to be awfully tiring
The two main differences between solid tires and air-filled tires are hysteresis ratio and penetration resistance response curve.
The former concerns how the tire behaves when it rolls on a flat surface. When a tire rolls, the section of tire immediately in front of the contact patch starts to deform itself, which takes energy, and the section right behind the contact patch "pushes the road back down", which releases about the same amount of energy it took to deform the tire about to make contact with the road, minus a little something (rolling resistance).
An air-filled tire has very low hysteresis, meaning that it releases most of the energy it has acquired by deformation instantly. A solid tire also releases most of the energy it has acquired, but with a small delay. That's because air itself has a low hysteresis and the tire walls are thin, but rubber has a high hysteresis.
Therefore, when a wheel turns slowly, there isn't much difference in rolling resistance between solid and air-filled tires. It's at high speed that a solid tire will start to steal all your energy and heat up, because the energy you put in to deform it gets released too late, after the rubber has left contact with the road. This means that solid tires are adequate in low-speed applications such as an everyday wheelchair, and air-filled tires are better for fast wheelchairs used in handisports.
As for penetration resistance, an air-filled tire gets deformed at the contact patch, but uses all the air inside the tire as shock absorber (the pressure in the tire doesn't rise significantly when a wheel hits a bump). In a solid tire, only the material right under the contact patch is deformed, which gives the wheel a much harsher ride. Again, in a low-speed application like an everyday wheelchair, the difference in harshness is certainly there, but it's not a huge problem like it would be hitting bumps with solid tires at 15mph.
So no, in an everyday wheelchair, it's not significantly more tiring to roll on solid tires than on air-filled tires. Even if it is a little, the pro of never getting a flat outweigh the con of pushing a bit harder. When a wheelchair user engages in a sport however, that's different, and air-filled tires are much better. A flat in that context is much more acceptable.