Contents: Definitions ↡ Checking and adjusting ↡
Definitions
The geometry of a vehicle's steering and suspension is determined by four angular values - all angles are expressed in degrees (convergence can also be expressed in linear units); the steering axis is taken to be an imaginary line passing through the suspension strut axes, extended, where necessary, to contact with the ground.
Camber is the angle between each wheel and a vertical line through its center and the tire contact point, when viewed from the front or rear of the vehicle. Positive camber is when the tops of the wheels are angled outward from the vertical line; negative camber when they are tilted inward.
The front camber angle is adjusted by loosening and rotating the front lower arm axle bolt and can be adjusted using a camber measuring device. The rear camber is not adjustable and is provided for reference only. It can be checked using a device and, if the obtained value differs significantly from the required value, the car should be checked at a service station, since the deviation may be caused by damage to the body or suspension components.
Caster is the angle between the steering gear axis and a vertical line through the center of each wheel and the tire pivot point, when viewed from the side of the vehicle. Positive caster is when the axis is tilted so that it intersects the horizontal line ahead of the perpendicular; negative slope when the line crosses the horizontal line beyond the vertical.
The front wheel tilt is adjusted by loosening and rotating the rear lower arm axle bolt and can be adjusted using a special device for determining the longitudinal tilt of the strut axle. The longitudinal tilt of the rear wheels is not adjustable and is provided for reference only. It can be checked using a device and, if the obtained value differs significantly from the required value, the car should be checked at a service station, since the deviation may be caused by damage to the body or suspension components.
Toe is the difference between the lines running through the centers of the wheels and the center line running through the car when viewed from above. Toe is in when the wheels are facing inward, and toe is out when the front wheels are facing outward (from each other).
Front wheel toe-in is adjusted by turning the steering rod ball joints in or out to change the effective length of the steering rod.
The rear wheel alignment is also adjusted. It is changed by loosening and turning the inner axle bolt of the lower rear wishbone.
Checking and adjusting
Since precise checking of the front wheel alignment requires special equipment and the skill to use it, it is recommended to perform this check and adjustment at service stations. If the car owner decides to perform such an adjustment himself, then a description of this procedure is given below. Note that most shops selling tires have devices for checking the wheel alignment angles in their assortment.
Setting the front track alignment
To check the fitment, the first thing to do is to buy a fixture. There are two types of fixture. The first, called a "tui", measures the distance between the front and rear inner rims of the wheels when the car is stationary. As previously described. The second type, known as a "wear pad", measures the actual position of the tyre contact surface on the road surface when the car is moving. This is achieved by mounting the front wheels of the car on a plate, which is then moved slightly according to the wear of the tyres and shows this movement on a scale. Both types of fixture have their advantages and disadvantages, but if the method is used correctly, each will give a satisfactory result.
When checking, make sure the steering wheel is in the direction of straight-ahead travel.
If adjustment is necessary, apply the parking brake, then jack up the front of the vehicle and support it on stands.
First, clean the threads of the tips. If the tips are rusted, apply a compound to the tips to facilitate the loosening of threaded connections before starting the adjustment. Loosen the inner joint clamp bolt, the lock nut and the clamping ring of the outer joint.
Change the length of the steering rod by screwing in or out the ball joints by rotating the steering rod using pliers; shortening the tie rod will decrease toe-in / increase toe-out.
After completing the adjustment, hold the steering rod and tighten the inner joint clamp bolt to the required torque. Tighten the outer joint clamp ring to the required force and securely tighten the lock nut.
If, after adjustment, the steering wheel spokes deviate from the horizontal position with the wheels installed in the direction of straight-ahead travel, remove the steering wheel and reposition it (see paragraph 17).
Check that the toe-in has not changed when the vehicle is lowered to the ground; adjust again if necessary.
Setting the camber and longitudinal tilt of the rack axis
If you have access to a camber and caster measuring tool, you can check the angles as follows. Both angles are adjusted simultaneously, since any change in camber also affects caster and vice versa.
Install the fixtures on the vehicle and check that the camber and caster angles of the kingpin are within the permissible values.
If adjustment is required, loosen the clamps securing the stabilizer bar to both front lower control arms. Also loosen the lower control arm pivot bolt nuts.
Rotate the bolts until the desired camber and tilt angles are achieved. Then, holding the bolt still, tighten the axle bolt nuts to the specified torque.
Check that both angles are set correctly, then tighten the stabilizer bar mount clamp nuts to the required torque and remove the tools.
Rear wheel alignment adjustment
The procedure for checking the rear wheel alignment is similar to that described for the front wheels.
To adjust the alignment, loosen the nut on the lower crossmember inner axle bolt. Turn the bolt until the toe is set correctly. Then, holding the bolt still, tighten the bolt nut to the specified torque.
Check that the toe-in has not changed by lowering the vehicle to the ground. If necessary, repeat the adjustment.