Toe is the inclination of the wheel front and rear as seen from above the vehicle. The wheel installation angle is called the toe angle. When the front of the wheels are closer than the rear of the wheels, this is called “toe-in”. The opposite arrangement is called “toe-out”. Roll of toe angle Conventionally, the primary purpose of toe angle has been to cancel out the camber thrust generated when camber is applied. Toe angle therefore prevented the front of the wheel from opening to the out side when toe-in was applied for positive camber. As a result of an increasing use of negative camber and improved performance of the tires and suspension in recent years, however, the need to cancel camber thrust has diminished. Thus, the primary purpose of toe angle has changed to ensuring straight-line stability. When a vehicle rides up on an incline on the road surface, the body tilts to one side. The vehicle feels as if it is about to turn in the direction in which the body is tilted. If the front of each wheel is turned to the inside (toe-in), however, the vehicle will try to move in the direction opposite that in which the body is tilting. As a result, straight-line stability is maintained.

SERVICE HINT:

If toe-in is excessive, the side slip force causes uneven wear of the tires. If toe-out is excessive, it is difficult to secure straight-line stability.

HINT:

Side slip is the total distance that the left and right tires slip to the side while the vehicle is running. Both in the case of toe-in and negative camber, side slip occurs towards the outside.

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.

Toe-angle

To adjust toe-in, change the lengths of the tie rod connecting the steering knuckle arms. 1. In the type in which the tie rod is behind the spindles, increasing the tie rod length increases toe-in. In the type where the tie rod is in front of the spindles, increasing the tie rod length increases toe-out. 2. In the double tie rod type, toe-in adjustment is carried out with the lengths of the left and right tie rod kept identical. If the lengths of the left and right tie rods are different, even correct toe-in adjustment will bring about incorrect turning angle adjustment.

Camber and Caster

Click on the bulb mark or the underlined sentence. The adjustment methods for camber and caster depend on the model. Below are typical methods. Since the toe-in changes if the camber and/or caster are adjusted, the toe-in must always be checked after the camber and/or caster adjustment.

1. Separate camber adjustment On some models, the steering knuckle bolts can be replaced with camber adjusting bolts. Camber bolts have a smaller shank diameter allowing camber adjustment. This type of adjustment is used on strut type suspensions.

2. Separate caster adjustment The caster is adjusted by changing the distance “L” between the lower arm and strut bar by using the nut or spacer of the strut bar. This type of adjustment is used on strut type or double wishbone type suspension, in which the strut bar is located in front of or behind the lower arm.

3. Simultaneous camber and caster adjustment

(1) The eccentric cam type mounting bolt is at the inside end of the lower arm. Turning this bolt moves the center of the lower ball joint to incline and adjusts both the camber and caster. This adjustment method is used on strut type or double wishbone type suspensions.

(2) Turning the eccentric cam type mounting bolts at the front and rear of the lower arm changes the installation angle of the lower arm and changes the position of the lower ball joint. This adjustment method is used on strut type or double wishbone type suspensions.

(3) The upper arm mounting angle, that is, the upper ball joint position, is changed by increasing or decreasing the number and/or thickness of the shims. This adjustment method is used on double wishbone type suspensions.

Example of Camber and Caster

Adjustment

The following is an example of adjusting the Supra JZA80 (1998). (For details, refer to the Repair Manual.)

(1)Measure the camber and caster.

(2) As shown in the chart, read the distance from the marked point to 0 point.

(3) Adjust the front and/or rear adjusting cams according to the values read from the chart.

Turning Radius (Wheel Angle, Turning

Angle)

The type with a knuckle stopper bolt can be adjusted, but the type without this bolt cannot be adjusted.

HINT:

In the case of rack-and-pinion steering gear, the wheel angle is typically determined by the point at which the steering rack end makes contact with the steering rack housing. Consequently, there is usually no knuckle bolt. If the lengths of the left and right tie rod ends are different,

Rear Wheel Alignment

Rear wheel alignment of an independent rear suspension is accomplished by adjusting the camber and toe angle. The method of adjusting the camber and toe angle differs depending on the type of suspension. Some models have no mechanism for adjusting the camber.

The turning radius is the turning angle of the left and right front wheels during cornering. Giving the left and right different turning angles matches the centers of turning for all four wheels and increases the driving stability during cornering. For example, in the type of steering system in which the tie rods are located behind the spindles, if the left and right knuckle arms are mounted so as to be parallel with respect to the vehicle’s center line, the left and right steering angles will be equal (= ). Each wheel would turn around a different center (O1 and O2) even if they have the same radius (r1 = r2), so side slipping would be generated on one of the tires. However, if the knuckle arms are inclined with respect to the vehicle’s center line, because the left and right wheels have different turning angles ( < ), they can be set to turn with different turning radii (r1 > r2) and around the same center (O), so the proper steering angle can be obtained.

SERVICE HINT:

If the turning radius is improper, the inside or outside tire slips sideways during cornering and smooth turning is not possible. This also generates uneven wear on the side slipping tire.