> Steering a motorcycle is done by precessing the front wheel.
I've encountered this claim so many times over the years. The precession force I've observed when riding motorcycles, by moving the bars after the front wheel leaves the ground, is simply not that great. It's obviously not the primary force steering a motorcycle.
With the front tire in contact with the road, motorcycles can appear to steer from precession because they initiate turns unintuitively via inverted counter-steering. What's really happening is when you initiate a turn, the point at the road:tire interface immediately veers in the direction you pointed because of the tire's grip with the road. But since this point is well below the center of gravity of the motorcycle, instead of steering the entire bike in that direction, the bike falls down and leans in the opposite direction. Thanks to the angle of the fork there's a complementary geometric relationship between the bike's lean angle and the front wheel's steering angle in the direction of the lean. These are the primary mechanisms steering a motorcycle.
The same mechanism is present in automobiles, which also have a significant distance separating the road:tire interface from the center of gravity. But in those vehicles it's exhibited as body roll, which is then necessarily resisted by the suspension components like springs and anti-sway bars. Nobody claims precession causes automobile body roll, because it's more obvious what's going on there - and the driver doesn't steer backwards briefly at the start of every turn.
Precession is a fun demonstration in science class, and does enable a motorcycle rider to exert some control when on one wheel. But it simply isn't the primary mechanism steering a motorcycle.
I've encountered this claim so many times over the years. The precession force I've observed when riding motorcycles, by moving the bars after the front wheel leaves the ground, is simply not that great. It's obviously not the primary force steering a motorcycle.
With the front tire in contact with the road, motorcycles can appear to steer from precession because they initiate turns unintuitively via inverted counter-steering. What's really happening is when you initiate a turn, the point at the road:tire interface immediately veers in the direction you pointed because of the tire's grip with the road. But since this point is well below the center of gravity of the motorcycle, instead of steering the entire bike in that direction, the bike falls down and leans in the opposite direction. Thanks to the angle of the fork there's a complementary geometric relationship between the bike's lean angle and the front wheel's steering angle in the direction of the lean. These are the primary mechanisms steering a motorcycle.
The same mechanism is present in automobiles, which also have a significant distance separating the road:tire interface from the center of gravity. But in those vehicles it's exhibited as body roll, which is then necessarily resisted by the suspension components like springs and anti-sway bars. Nobody claims precession causes automobile body roll, because it's more obvious what's going on there - and the driver doesn't steer backwards briefly at the start of every turn.
Precession is a fun demonstration in science class, and does enable a motorcycle rider to exert some control when on one wheel. But it simply isn't the primary mechanism steering a motorcycle.