Unity3D - Collision Part 2

Wheel Collider

The Wheel Collider is a special collider for grounded vehicles. It has built-in collision detection, wheel physics, and a slip-based tire friction model. It can be used for objects other than wheels, but it is specifically designed for vehicles with wheels.

PROPERTIES

Center	Center of the wheel in object local space.
Radius	Radius of the wheel.
Suspension Distance	Maximum extension distance of wheel suspension, measured in local space. Suspension always extends downwards through the local Y-axis.
Suspension Spring	The suspension attempts to reach a Target Position by adding spring and damping forces.
Spring	Spring force attempts to reach the Target Position. A larger value makes the suspension reach the Target Position faster.
Damper	Dampens the suspension velocity. A larger value makes the Suspension Spring move slower.
Target Position	The suspension's rest distance along Suspension Distance. 0 maps to fully extended suspension, and 1 maps to fully compressed suspension. Default value is zero, which matches the behavior of a regular car's suspension.
Mass	The Mass of the wheel.
Forward/Sideways Friction	Properties of tire friction when the wheel is rolling forward and sideways.