Camber thrust and camber force are terms used to describe the force generated perpendicular to the direction of travel of a rolling

tire A tire (American English) or tyre (British English) is a ring-shaped component that surrounds a wheel's rim to transfer a vehicle's load from the axle through the wheel to the ground and to provide traction on the surface over which t ...

due to its

camber angle Camber angle is one of the angles made by the wheels of a vehicle; specifically, it is the angle between the vertical axis of a wheel and the vertical axis of the vehicle when viewed from the front or rear. It is used in the design of steering a ...

and finite contact patch. Camber thrust is generated when a point on the outer surface of a leaned and rotating tire, that would normally follow a path that is elliptical when projected onto the ground, is forced to follow a straight path while coming in contact with the ground, due to

friction Friction is the force resisting the relative motion of solid surfaces, fluid layers, and material elements sliding against each other. There are several types of friction: *Dry friction is a force that opposes the relative lateral motion of ...

. This deviation towards the direction of the lean causes a deformation in the tire tread and carcass that is transmitted to the vehicle as a force in the direction of the lean. Camber thrust is approximately linearly proportional to camber angle for small angles, reaches its steady-state value nearly instantaneously after a change in camber angle, and so does not have an associated

relaxation length Relaxation length is a property of pneumatic tires that describes the delay between when a slip angle is introduced and when the cornering force reaches its steady-state value. It is also described as the distance that a tire rolls before the late ...

. Bias-ply tires have been found to generate more camber thrust than

radial tires A radial tire (more properly, a radial-ply tire) is a particular design of vehicular tire. In this design, the cord plies are arranged at 90 degrees to the direction of travel, or radially (from the center of the tire). Radial tire construction ...

. Camber stiffness is a parameter used to describe the camber thrust generated by a tire and it is influenced by inflation pressure and normal load. The net camber thrust is usually in front of the center of the wheel and so generates a camber torque, twisting torque, or twisting moment. The orientation of this torque is such that it tends to steer a tire towards the direction that it is leaned. An alternate explanation for this torque is that the two sides of the contact patch are at different radii from the axle and so would travel forward at different rates unless constrained by friction with the pavement.

On bikes

On bicycles and

motorcycle A motorcycle (motorbike, bike, or trike (if three-wheeled)) is a two or three-wheeled motor vehicle steered by a handlebar. Motorcycle design varies greatly to suit a range of different purposes: long-distance travel, commuting, cruising ...

s, camber thrust contributes to the centripetal force necessary to cause the vehicle to deviate from a straight path, along with

cornering force Cornering force or side force is the lateral (i.e., parallel to wheel axis) force produced by a vehicle tire during cornering. Cornering force is generated by tire slip and is proportional to slip angle at low slip angles. The rate at wh ...

due to the

slip angle In vehicle dynamics, slip angle or sideslip angle is the angle between the direction in which a wheel is pointing and the direction in which it is actually traveling (i.e., the angle between the forward velocity vector v_x and the vector su ...

, can be the largest contributor, and in some cases is the sole contributor. Camber thrust contributes to the ability of bikes to negotiate a turn with the same radius as automobiles but with a smaller steering angle. When a bike is steered and leaned in the same direction, the camber angle of the front tire is greater than that of the rear and so can generate more camber thrust, all else being equal.

On automobiles

automobile A car or automobile is a motor vehicle with wheels. Most definitions of ''cars'' say that they run primarily on roads, seat one to eight people, have four wheels, and mainly transport people instead of goods. The year 1886 is regarde ...

s, camber thrust may contribute to or subtract from the total centripetal force generated by the tire, depending on the camber angle. On a well-aligned vehicle, camber thrust from the tires on each side balances out. On a surface rough enough for one front tire to momentarily lose traction, camber thrust from the other front tire can cause the vehicle to wander or feel skittish.

References

{{Tires, state=collapsed Tires Motorcycle technology Motorcycle dynamics Automotive steering technologies Vehicle technology

On bikes

On automobiles

See also

References