It's All About Traction
The amount of force, in pounds, exerted on the sidewalls ofthe tire per square inch
– or PSI
The area of the tire that touches the ground, or the
TIRE PATCH, creates a frictional force called
TRACTION with the surface. Tires with too high or low of pressure do not
have the optimal size tire patch which causes problems with surface traction.
- Rolling resistance
- damage: popped tube
- little comfort
- + rolling resistance
- + damage: pinch flat
- - responsiveness
Riders should adjust their tire pressure based on their WEIGHT to optimize the tire patch size.
Adjust tire pressure to accommodate for:
- Road or trail conditions
smooth pattern, like on a road bike, decreases resistance with pavement
knobby pattern, like on a mountain bike, helps keep traction with
A tire with a smaller diameter accelerates faster, however a larger diameter tire will clear obstacles easier due to the IMPACT ANGLE.
Is the Wheel Defying the Laws of Physics?
Have you ever noticed that it seems difficult to balance your bike when moving at very slow speeds? When you pedal, you increase your speed and create angular momentum which helps you maintain a stable, upright position.
Low angular momentum
High angular momentum
A rotating bicycle wheel acts as a gyroscope. It is thought that the gyroscopic effect plays a major role instability and control when riding a bike. A gyroscope is based on the principle of angular momentum.
angular momentum = moment of inertia × angular velocity
moment of inertia: describes an objects tendency to resist angular acceleration
moment of inertia = mass × radius 2
angular momentum = mass x radius 2 × angular velocity
When a wheel is spun, it develops angular momentum which causes the wheel to resist changes in orientation as explained by the law of conservation of momentum. This states that the angular momentum must remain constant in both magnitude and direction unless acted on by an outside force.
angular momentum initial = angular momentum final
Although the gyroscope tries to maintain its orientation, outside forces such as friction act on the gyroscope causing it to eventually lose its angular momentum as the wheel’s speed decreases.