HowStuffWorks: How Motorcycles Work

At least the explanation of motorcycle steering doesn’t invoke magical gyroscopic stability, but it does assert that countersteering works because of gyroscopic precession.

This motion is called precession, and it’s what causes the steering in motorcycles to be counterintuitive.

No mention is made of roll moments due to laterally accelerating contact patches or gravity, just precession.  Professor Cossalter in his excellent Motorcycle Dynamics, on page 304 of the second edition, calculates the roll moment generated by gyroscopic effect for a motorcycle traveling at 22 m/s (79 km/h or 49 mph) to be 3.5 N-m (2.6 lb-ft) and compares it to the roll moment generated by the accelerating contact patches of 30 N-m (22 lb-ft), which is 8.6 times larger. He concludes with the note that the gyroscopic effect is present from the instant torque is applied at the handlebars, and the roll moment generated by the lateral force of the tires can take some time, ~0.1 seconds in this example, to build up.

So gyroscopic effect is neither necessary nor sufficient for steering in motorcycles to be counterintuitive. Instead, steering in motorcycles is counter intuitive because countersteering is necessary, and countersteering is necessary because motorcycles are single-track vehicles that must lean into a turn. Finally, countersteering works because of the roll moment generated by laterally accelerating contact patches, the force of gravity acting on the center of mass, and to a small amount, if spinning wheels are present, gyroscopic precession.

If you are going to explain how stuff works, it probably helps to learn how stuff works first.


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