Mad Scientist, hope you remember to put centripetal force in there? It's a biggie on a 500+ lb bike cornering at high speed.

Centripetal force is there indeed. What I didn't include was friction and normal force. For a thin wheel, one can approximate they lie on the origin of axes (as i draw them), which is exactly crossed by th wheel longitudinal axis (hence they don't enter into the moment calculation). But for a broad wheel like there are on motorbikes, the point of application will be obviously offset. This is not difficult to include conceptually, but that gores up (does that word exist?) the formulas a bit.

Note that, with my formula, phi always has a solution, which means the ~~bike~~ wheel can be at equilibrium at any lean angle. This is obviously not true in reality (the bike falls), where more stuff (see previous post) must be taken into account.