I've been fascinated by motorcycles since I was a child. I've owned and ridden them since I was a teenager. What keeps a motorcycle on two wheels?What are the physical forces behind the simple (OK, not so simple) act of riding a motorcycle?
Lean angles, countersteering, force vectors, rotational velocity, inertia, inverted pendulums... what's with all this stuff?
The boring physics of steering a Motorcycle (YouTube)
Motorcycle Physics (YouTube)
The Lazy Motorbike: Countersteering, a physical View on it. (YouTube)
Officers study physics of motorcycle crashes (ksl.com)
Motorcycle Physics Resources on the Web
Well, I don't think you can do much better than this terrific page titled The Physics of Motorcycles on MotorcycleJazz.com. Go there and read it right away! We'll be here when you get back.
"Question: If you are on a motorcycle going down the highway, and you press on the inside of the left handle grip, why do the wheels turn to the right, but you turn to the left?" Answer here
Despite what some people may think, motorcycle roadracing is not only a highly strenuous sport, but there is MUCH more involved than just twisting the throttle and turning the handlebars. The Physics of Motorcycle Racing
This page contains a limited bibliography of technical papers related to the modling [sic] and simulation of motorcycle dynamics. Much of the work has been done in the UK, where Prof. Robin Sharp works with the same symbolic code generator (VehicleSim Lisp, formally known as AutoSim) used by Mechanical Simulation.
To find the essence of bicycle self balance we looked at simpler and simpler dynamical models until we found a minimal two-mass-skate (TMS) bicycle that theory told us should be self-stable. This bicycle has no gyroscopic effect and no trail. We built a bicycle (of sorts) based on the theory to prove the point.
This bicycle proves that self-stability cannot be explained in any simple words. Bicycles are not stable because of gyros, because you can make a self stable bicycle without gyros. We did that. And they are not stable because of trail, you can take that away too. And we did that. More positively, we have shown that the distribution of mass, especially the location of the center of mass of the front assembly, has as strong an influence on bicycle stability as do gyros and trail.
Why can a bicycle balance itself? One necessary condition for bicycle self stability is (once we define the words carefully) that such a bicycle turns into a fall.