Well, can we assume that air leaking out of a tire follows Darcy's Law for the rate of flow through a permeable membrane?



While the pressure difference is much lower (it's hard to get a bare inner tube much beyond a few psi), the path length of the material should also be significantly less. I'm not quite topologically adept enough to figure out the surface areas of the torus, in fact I'm kind of stuck on it. Does anyone more mathematically inclined want to chime in?

I'm inclined to think it's going to be an inverse square thing, but I can't actually justify that assumption just yet.