Alignment installation cannot be carried out without the appropriate equipment. Therefore, only the basic concepts necessary for setting the wheel alignment are described here.
Convergence
Convergence is the angle at which the plane of the wheel deviates from the longitudinal axis of the car. Positive toe means that the wheels, when measured at wheel center height, converge slightly closer at the front than at the rear. Negative toe means that the front wheels diverge more than the rear.
For a Mercedes car, both front and rear wheels have positive toe: front wheels - 0°25' (sports suspension 0°10'), rear wheels - 0°25'.
Camber and transverse inclination of the king pin
Front axle
St - collapse; Sp is the transverse inclination of the kingpin; 4 - lower suspension arm; 5 - steering knuckle 6 - upper suspension arm; 7 - knuckle joint; 19, 20 - bolts with an eccentric; +/-3 - installation stroke - 3 mm
The camber and lateral tilt of the kingpin reduces the transmission of shocks to the steering and ensures minimal friction when cornering.
Camber is the angle at which the plane of the wheel deviates from the vertical. The front wheels are thus further apart at negative camber at the point of contact with the road than from above. The front and rear wheels of a Mercedes have negative camber.
The transverse inclination of the kingpin is the angle between the axis of rotation of the fist and the vertical at the point where the wheel is standing, when viewed in the longitudinal direction of the car.
The camber and lateral inclination of the kingpin together determine the so-called running-in shoulder. Thanks to appropriate design data, greater directional stability is achieved when braking, especially if the wheels are on different road surfaces (for example, if the left wheel brakes on a dry road and the right wheel brakes on a wet road).
Longitudinal inclination of the kingpin back
The longitudinal inclination of the kingpin back is the angle between the axis of rotation of the fist and the vertical in the transverse direction. This tilt greatly affects the front wheel control when driving in a straight line. Slight tilt favors yaw when driving on bad roads or in crosswinds, and when cornering, the steering wheel does not return to the center position well.
Longitudinal inclination together with camber is set using two eccentric bolts on the suspension arms.
Prerequisites for verification
- prescribed tire pressure;
- the car is not loaded, but prepared for the trip: a full tank, a spare wheel and a tool - all this should be when checking;
- shake the suspension strongly beforehand;
- the steering wheel is straight;
- adjusted play in the suspension arms;
- wheel bearing play adjusted.
Checking / setting the positive convergence of the front wheels
The position of the front wheels when viewed from above
Accurate wheel alignment must only be carried out by a specialist workshop. With one-sided tire wear, the toe-in should be checked in general. The convergence is checked if parts of the steering trapezoid were removed. Toe-in can be checked by relatively simple means.
The above prerequisites for verification must be met.
1. Set the wheels straight, the crossbar of the steering wheel should be located horizontally.
2. The middle position is reached when the groove at the junction of the steering joint coincides with the marking mark on the steering gear (arrow). If at the same time the steering wheel is not quite straight, remove it and rearrange it.
3. Place a sliding bar between the front wheels in front and push it apart with a force of about 100 N (corresponds to 10kg). To do this, use branded special equipment or a similar rod. The extension is necessary in order to simulate the movement when the wheels tend to move outward.
4. Measure convergence. The total convergence of the front wheels should be 0°25'±10' (for sports suspension 0°10'±10'). This means that the edges of the rim at the front should be 1mm closer than at the back.
5. Set positive toe by turning the steering linkage lever on the hex (10th). Pre-release the clamping cone (10f), while holding the lever by the hexagon with an open-end wrench.
6. Set the positive convergence with the same angle on the left and right, while the steering wheel should be in the middle position.
7. Tighten clamping cone (10f) torque of 50 Nm, while holding the steering trapezoid lever by the hexagon with an open-end wrench. Check the ball joint collar, it must not be creased or damaged. After verification (installations) remove the wheel spreader.