Wheel alignment and camber / transverse and longitudinal inclination of the kingpin
Wheel toe-in is the difference between the distances measured in front and behind the steered wheels at the height of their axis of rotation from the road. As a rule, the front wheels should have a positive convergence, since they - due to camber and rolling resistance - roll somewhat outward when moving in a straight line, since there are minor gaps in the wheel bearings, in the suspensions and in the tie rod joints. Positive toe limits the tendency of the wheels to roll outward. With positive wheel alignment, the distance between the wheels in front is less than the distance behind. With negative toe-in, on the contrary, the smaller distance between the wheels will be at the rear.
VW PASSAT cars are equipped with zero toe-in (0°). It must be borne in mind that on vehicles with power steering, toe adjustment can only be carried out on the right tie rod.
The camber and lateral tilt of the kingpin reduce the transfer of shock loads from the road to the steering and keep the moment of friction of the wheels on the road when cornering to a minimum.
Camber is the inclination of the plane of the front wheel relative to the vertical plane (the figure shows a positive camber with the wheel plane tilted at an angle a). VW PASSAT vehicles have a negative camber angle. The prescribed camber angle is -1°20'±20'; with an engine power of 150 hp and VR6 engine: -1°10±20': for cross-country vehicles: -1°±20'. Camber adjustment can only be carried out in the connection of the wheel bearing housing with the shock absorber strut,
The transverse inclination of the kingpin is characterized by the angle p between the axis of the kingpin and the vertical passing through the point of contact of the tire with the road, when viewed in the direction of the vehicle.
The camber angle of the wheels and the angle of the transverse inclination of the kingpin have a joint effect on the so-called running-in shoulder - the distance between the center of the bearing surface of the tire of the steered wheel and the point of intersection of the axis of the kingpin with the road. The smaller the break-in shoulder, the easier the car is to drive.
The shocks transmitted from the side of the road to the steering also become significantly weaker.
The longitudinal inclination of the kingpin is characterized by the angle between the axis of the kingpin and the vertical passing through the point of contact of the tire with the road, when viewed in a direction perpendicular to the direction of the vehicle.
The longitudinal inclination of the kingpin has a proportional effect on the straightness of the movement of the front wheels. A slight longitudinal inclination of the kingpin causes a deviation from a straight-line movement on a bad road or with a side wind, and also forces the steering to not fully return to the neutral position after a turn.
Adjustment
To determine the parameters of the undercarriage, a viewing hole or a lifting platform is required. For each parameter definition, the following prerequisites must be met:
- The tire pressure corresponds to the prescribed value,
- Perfectly flat horizontal surface for measurements.
- The vehicle is unloaded.
- The car is preliminarily strongly elastically deformed.
- Steering is properly adjusted.
- No unacceptable clearances in the steering gear.
- No impermissible gaps in wheel suspensions.
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