after contemplating how rollers work, and how a track stand works, one should be able to recognize that gyroscopic forces have almost nothing to do with keeping a bike upright. If you could make a bicycle with zero diameter wheels, it would still be ridable. Try riding a bike on rollers when someone is holding your handlebars. It doesn't work. You have to be able to keep the center of gravity balanced with the reaction forces at the wheels. A bike with a very stiff headset is also incredibly difficult to ride.