Frequent inspection and correction of wheel alignment are ordinarily not necessary under normal conditions of use. However, if the tires are worn unevenly, if steering is unstable, or if the suspension has had to be repaired due to an accident, the wheel alignment must be inspected and corrected.

1. General

Wheel alignment covers several items such as camber, caster, steering axis inclination, etc., and each item is closely related to the other items. When inspecting and correcting, it is necessary to consider all items and how they relate to each other.

2. Where to measure and cautions concerning tester handling

Recently a large number of new alignment tester models have come into use. However, note that the high-precision testers may be quite complex, and errors may occur without your being aware of it. Therefore, maintenance of the testers must be performed periodically to assure that they are always reliable. Always measure wheel the alignment with the vehicle parked on a flat, level area. This is necessary because, no matter how accurate the alignment tester is, correct values cannot be obtained if the place where the measurement are to be carried out is not level.

3. Necessity of inspection before measurement of wheel alignment

Before measuring the wheel alignment, each factor that could affect the wheel alignment must be checked and necessary corrections made. Proper execution of this preparatory operation will give the correct values. Standard wheel alignment values are determined by the manufacturer with the vehicle in its “normal” condition. Therefore, when inspecting wheel alignment, it is necessary to have the vehicle as close to its normal condition as possible in which standard values are determined. (See Repair Manual for standard values.) Items to be checked before measurement of wheel alignment area.

• Tire inflation pressure (under standard conditions)
• Markedly uneven wearing of tires or difference in the sizes.
• Tire runout (radial and face)
• Ball joint play due to wear
• Tie rod play due to wear
• Front wheel bearing play due to wear
• Lengths of left and right strut bars
• Difference between left and right wheelbase
• Deformation or wear of steering linkage parts
• Deformation or wear of parts related to front suspension
• Lateral body inclination (chassis ground clearance)

4. Importance of chassis-to-ground clearance

adjustment before alignment measurement

In a vehicle with independent front suspension, wheel alignment factors will vary depending upon the load because of changes in chassis-to-ground clearance. It is therefore necessary to specify the wheel alignment factors for the specified clearance. Unless otherwise specified, refer to the Repair Manual, etc.

5. Road test

After adjusting the front axle, suspension, steering, and/or front wheel alignment, carry out following road test to check the result of the adjustments:

Straight-ahead driving

(1) The steering wheel must be at the correct position

(2) The vehicle should run straight ahead on a flat road.

(3) Excessive steering shimmy or flutter should not occur.

Turning

The steering wheel should turn easily in either direction, and should return quickly and smoothly to the neutral position when released.

Braking

The steering wheel should not pull to either side when the vehicle is broken on a flat, smooth road.

Checking for abnormal noise

No abnormal noise must be heard during the driving test.

6. Measurement results and how to use them

If the measured values deviate from the standard values, it makes the measured values within the standard values by adjusting adjustment mechanisms or replacing parts.

The vehicle must have proper straightline performance for stable driving, cornering performance for driving around curves, recovery force for returning to the straight-line condition, the capacity to soften the shock transmitted to the suspension when the tires are impacted, etc. Therefore, the wheels of a vehicle are mounted at specific angles to the ground and specific suspensions for each purpose. This is called wheel alignment. The wheel alignment has the following five factors:

• Camber
• Caster
• Steering axis inclination (kingpin inclination)
• Toe (toe-angle, toe-in and toe-out)
• Turning radius (wheel angle, turning angle) If even one of these elements is incorrect, the following problems can occur:
• Difficult steering
• Poor steering stability
• Poor recovery on curves
• Shortened tire life

Tire uniformity refers to uniformity of weight, dimensions and rigidity. However, since uniformity of weight is ordinarily called “wheel balance”, and uniformity of dimensions (or rather, the lack thereof) is called “run-out”, uniformity alone usually refers to “uniformity of rigidity”. These greatly affect driving performance.

1. Wheel balance

It is necessary to balance the wheel assemblies properly in order to eliminate vibrations and this operation is what is called wheel balancing. Wheel balancing involves balancing the weight of the entire wheel assembly-that is, the disc wheel with the tire attached. Wheel balance can be divided into “static balance”( that when the wheel assembly is at rest) and “dynamic balance” (that when it is rotating). HINT: There are off-the-car balancers that balance the tires alone and on-the-car balancers that balance the tire with the rotating parts such as the disc brake rotor and axle hubs.

2. Run-out

Run-out is defined as the apparent change in a tire dimensions during rotation. Run-out is measured by holding a dial gauge against the surface of the tire, rotating the tire, and observing the fluctuations of the indicator needle on the gauge. There are two types of run-out: that in the tire’s radial direction (radial run-out), and that in the axial direction (lateral run-out).

3. Uniformity

The tire is subject to subtle fluctuations in the way it flexes as it rotates. These fluctuations introduce a periodic variation in the force which it receives from the road surface. This force can be resolved into three components:

Radial Force Variation (RFV) Fluctuation in the vertical force acting upwards toward the tire’s center. (parallel to the tire’s radius)

Lateral Force Variation (LFV) Fluctuation in the horizontal force acting parallel to the tire’s axis.

Tractive Force Variation (TFV) Fluctuation in the horizontal force acting parallel to the tire’s direction of motion.

SERVICE HINT:

Vibration Tire vibration problems are divided into body shake, steering flutter, and steering shimmy. Body shake is defined as vertical or lateral vibration of the vehicle body and steering wheel, along with vibration of the seats. Shimmy and flutter are defined as vibration in the steering wheel in its rotational direction.