Down-force and Grip

March 10, 2010 Accessories, Cars No Comments

A car turns by turning the front wheels left or right. This puts the tires at angle compared to the direction of motion. Due to friction between the road surface and the tire, the tire resists forward motion and redirects the motion to the direction of the tire. This change in direction applies first in the front of the car where the turning tires are located. This turning, therefore, puts the entire car at an increasing angle against the forward motion. The rear tires, which are fixed in relation to the angle of the entire car, resist the original forward motion, also through friction, and gradually shift the motion of the car to the direction of the front wheels.

Friction is based on the weight of the car and the area of contact of the tires and the road. Since the weight of the car is relatively large, the frictional forces at slow speed exceed the force of inertia, which is based on speed and direction. When the speed of the car is high enough, the force of inertia can exceed the forces of friction of the tires causing them to slip or lose grip of the road. This cause the rear wheels to continue in the forward direction while the front wheels turn, causing loss of control or spin-outs. A spoiler is like a wing of a plane. A wing reacts with the rushing air outside the plane and forces it upward. A spoiler is a reverse wing that forces the car downward. This force is called down-force. Down-force adds with the weight of the car and increases the frictional forces between the tires and the road and increases its grip. Thus, a spoiler makes the car safer at high speeds and adds a sporty, speedy, look to a car that makes it attractive.