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Automotive
Wheel Alignment

Proper alignment of both the front and the rear wheels of your car ensures, reduction in fuel consumption, longer tire life, easier steering, less strain on the parts that make up steering and suspension of the vehicle, not to mention greater safety in driving. The alignment angles are designed in the vehicle to properly locate the vehicle’s weight on the moving parts and facilitate steering. If these angles are not correct, the vehicle is misaligned. When you get your car aligned your technician is just restoring these angles to original angles specified the design engineers.

Basic Wheel Alignment Angles

Caster

The angle of the steering axis of a wheel from the vertical, as viewed from the side of the vehicle.
The forward or rearward tilt from the vertical line is caster.
Tilting the wheel forward is negative caster.
Tilting the wheel backward is positive caster.
Caster is designed to provide steering stability.
The caster angle for each wheel on an axle should be equal.
Unequal caster angles cause the vehicle to steer toward the side with less caster.
Caster is not related to tire wear.
Caster is effected by worn or loose steering parts such as strut rods and control arm bushings.

Camber

The angle represented by the tilt of either the front or rear wheels inward or outward from the vertical as viewed from the front of the car.
Camber is designed into the vehicle to compensate for road crown, passenger weight, and vehicle weight.
Camber means each wheel is tilted outward or inward the same amount.
Unequal camber causes tire wear and causes the vehicle to steer toward the side that is more positive.
Incorrect camber angles causes the inside and outside of the tire to have different diameters.
Wear from incorrect shows up on either the outside or inside of the tire tread.

Toe

Toe is the distance comparison between the leading edge and trailing edge of the front tires.
If the leading edge distance is less, than there is toe-in.
It the leading edge distance is less, then there is toe out.
Toe is critical as a tire wear angle.
Wheels that do not track straight ahead have to drag as they travel forward.
Excessive toe (in or out) cause a sawtooth edge of the tread surface from dragging the tire sideways.
Excessive toe-in will cause a tire to wear on the outside edge. Toe-out causes wear on the inside edge.

Thrust Line Alignment

A main consideration in any alignment is to make sure the vehicle runs straight down the road, with the rear wheels tracking directly behind the front tires when the steering wheel is in the straight-ahead position.
The geometric centerline of the vehicle should parallel the road
This is the case when rear toe is parallel to the vehicle's geometric centerline in the straight-ahead position.
If the rear toe does not parallel the vehicle centerline, a thrust direction to the left or right is created.
This difference of the rear toe from the geometric centerline is called the thrust angle. The vehicle tends to travel in the direction of the thrust line, rather than straight ahead.

Steering Axle Inclination

Steering Axle Inclination locates the vehicle weight to the inside or outside of the vertical centerline of the tire.
The steering axle inclination is the angle between true vertical and a line drawn between the steering pivots as viewed from the front of the vehicle.
It is an engineering angle designed to project the weight of the vehicle to the road surface for stability.
The steering axle inclination helps the vehicle's steering system return to straight ahead after a turn.

Tuning Radius

Turning Radius is the amount of toe-out present in turns.
Tuning radius is also called "toe-out on turns" or " turning angle".
As a car goes around a corner, the inside tire must travel in a smaller radius circle than the outside tire.
This is accomplished by designing the steering geometry to turn the inside wheel sharper than the outside wheel.
The result can be seen as toe-out in turns.

Tracking

All vehicles are built around a geometric centerline that runs through the center of the chassis from the back to the front.

The thrust line is the direction the rear axle would travel if affected by the front wheels.

This condition is called tracking.

An ideal alignment has all four wheels parallel to the centerline, making the thrust line parallel to the centerline.

However, the rear-wheels thrust line of the a vehicle might not always be parallel to the actual centerline of the vehicle, so the angle of the thrust line must be checked first.

When the car is tracking correctly, its rear wheels are the same distance from the front wheels on both sides.

Automotive Wheel Alignment