Independent wheel suspensions, in particular front wheel suspensions, for vehicles built on a frame and that include a pair of longitudinal members of U- or I-shaped profile are most commonly of the McPherson-type, or comprise double suspension arms. Such solutions are usually difficult to fit because of the limited space available for their installation. This presents particular problems in the case of front wheel suspensions in which the space is severely limited by the location of the engine between the longitudinal frames. An alternative is to shift the engine, which is often the case in buses, so that the engine is located at the back of the vehicle.
Examples of various types of known independent wheel suspensions are disclosed in DE 2918605, DE 4412145, DE 19515565 and U.S. Pat. No. 4,033,605.
A further problem with current wheel suspensions is that they limit the possible ground clearance and the scope for locating the engine. It is desirable to have the facility for relatively free adjustment of the height of the chassis above ground level, while the engine needs to be located as low down as possible in order to achieve a low center of gravity and a level floor in the driver's cab. These requirements are difficult to achieve with current solutions that have sprung, rigid axles that extend under the frame and the engine.
A wheel suspension which to some extent solves the aforementioned problems is disclosed by SE 9903731 in which each wheel suspension is fixed in a sub-frame fitted around a pair of longitudinal members. The disadvantages with this solution are that it becomes complicated due to all the additional links needed to absorb longitudinal forces and to transmit steering movements, and that the sub-frame takes up a lot of space.
In addition, DE 4021096 demonstrates a relatively compact wheel suspension which affords good ground clearance, but this solution cannot be applied to steered front wheel suspensions and cannot absorb larger lateral forces.