Wheel Alignment & Tire Characteristics
1. Relationship Between Wheel Alignment and Vehicle Pulling to One SideWhen the cross camber or caster of the front wheel alignment is large, it can cause vehicle pulling.
WHEEL ALIGNMENT DIRECTION OF VEHICLE PULLING
Camber Vehicle pulls in direction of wheel with large camber value.
Caster Vehicle pulls in direction of wheel with small caster value.
If the cross camber or caster is within the specified range (30' or less), noticeable vehicle pulling will not occur due to side-to-side differences in camber or caster.
NOTE:
If the cross camber or caster is 30' or less and the steering wheel is released for 100 m (109 yards) when driving at 100 km/h (62 mph), the alignment-induced drift distance is approximately 0.5 m (1.64 ft).
2. Relationship Between Tire Characteristics and Vehicle Pulling to One Side
When radial tires are rotating, they have the characteristic of generating force in the lateral direction between the tire and the road surface. This lateral force is comprised of two factors:
^ Ply-steer, which changes direction according to the rotation direction of the tires.
^ Conicity, which is generated in a fixed direction regardless of the tire rotation direction.
If these lateral forces are too strong, vehicle pulling will occur.
a. Ply-Steer
Lateral force due to ply-steer is produced by the construction of the belts inside the tire tread. With radial tires, the wire of the belt is slanted as shown in the illustration below. Thus, it is in the lateral direction that tire tread easily changes shape (stretches), and lateral force is generated between the tire and the road surface in the lateral direction.
NOTE:
Lateral force from ply-steer prevents vehicle drift caused by road slant. so in many cases lateral force to the right is provided for left-handed steering vehicles.
b. Conicity
Conicity is lateral force resulting from uneven formation of the left and right sides of the tire. The direction the lateral force is exerted depends on the hardness of the side walls and the difference in height between the left/right sides of the tire.
NOTE:
^ In the case of vehicle pulling caused by tires, the lateral force which is exerted as a result of conicity has the greatest effect. If the steering wheel is released for 100 m (109 yards) when travelling at 100 km/h (62 mph), the vehicle may drift as much as 1.5 m (5 ft).
^ When vehicle pulling is due to conicity, the amount of drift can be reduced and the direction of drift can be changed by changing the location of the tire or reversing the tire when installing it on the wheel.
Repair Procedure Flow Chart