The coefficient of thermal expansion is much higher for rubber as well. I'm can't quote a reference, but I think it's about 7 X10-4/degree C, pretty large compared with aluminum or steel., I think they are about 2.5X10-5 and 1.9x10-5 respectively.
The expansion of the rim will be a complicated thing to compute as well. The aluminum rim will try to expand at a fater rate than the steel spokes, increasing the tension in the spokes and inducing compression in the rim.
Figuring out the how the whole assembly expands and contracts will be a tricky bit to do. The bead of the tire will be held to the rim, and the shape of the tire would distort a bit as temperature increases. I think the distance from the outermost limit of the tire to the rim will increase with temperature, but I'm not sure.
I'm pretty sure the elastic properties of the rubber increase with temperature as well, although this would be small compared to the changes in diameter. Pressure accounts for 99% of the support, but you can wheel a bike around on a flat, so the tire itself contributes a little.
Good data, and a remarkable puzzle.