Independent wheel suspensions – general

The chassis of a passenger car must be able to handle the engine power installed. Ever-improving acceleration, higher peak and cornering speeds, and deceleration lead to significantly increased requirements for safer chassis. Independent wheel suspensions follow this trend. Their main advantages are:

Ø little space requirement;

Ø a kinematic and/or elastokinematic toe-in change, tending towards understeering is possible;

Ø easier steerability with existing drive;

Ø low weight;

Ø no mutual wheel influence.

Driven, rigid steering axle with dual joint made by the company GKN – Birfield AG for four-wheel-drive special-purpose vehicles, tractors and construction machinery. The dual joint is centred over the bearings 1 and 2 in the region of the fork carriers; these are protected against fouling by the radial sealing rings 3. Bearing 1 serves as a fixed bearing and bearing 2 as a movable bearing. The drive shaft 4 is also a sun gear for the planetary gear with the internal-geared wheel 5. Vertical, lateral and longitudinal forces are transmitted by both tapered-roller bearings 6 and 7. Steering takes place about the steering axis EG.

The last two characteristics are important for good roadholding, especially on bends with an uneven road surface. Transverse arms and trailing arms ensure the desired kinematic behaviour of the rebounding and jouncing wheels and also transfer the wheel loadings to the body . Lateral forces also generate a moment which, with unfavourable link arrangement, has the disadvantage of reinforcing the roll of the body during cornering. The suspension control arms require bushes that yield under load and can also influence the springing. This effect is either reinforced by twisting the rubber parts in the bearing elements, or the friction increases due to the parts rubbing together , and the driving comfort decreases. The wheels incline with the body. The wheel on the outside of the bend, which has to absorb most of the lateral force, goes into a positive camber and the inner wheel into a negative camber, which reduces the lateral grip of the tyres. To avoid this, the kinematic change of camber needs to be adjusted to take account of this behaviour and the body roll in the bend should be kept as small as possible. This can be achieved with harder springs, additional anti-roll bars or a body roll centre located high up in the vehicle.