SUSPENSION SYSTEM
The system of springs, shock absorbers and linkages by which a vehicle is supported on its wheels. It allows relative motion between the chassis and the wheel. The purpose of the suspension system is to isolate the vehicle body from road bumps and vibrations, while keeping the wheels in contact with the road and thus provide good driving pleasure, and keeping vehicle occupants comfortable and a ride quality reasonably well isolated from road noise, bumps, and vibrations,etc
SUSPENSION TYPES
The main groupings are dependent and independent suspension types but this naming convention really only applies to traditional or analogue suspension systems. Even independent systems are typically joined across the car by an anti-roll bar and so are not truly independent. But now days the concept of fully independent suspension systems started to appear on cars where the anti-roll bar was replaced by sophisticated computer software connected to some form of electronically-controlled suspension.
FRONT SUSPENSION - DEPENDENT SYSTEMS
It is basically a solid bar under the front of the car, kept in place by leaf springs and shock absorbers. It's still common to find these on trucks.
Solid front axles weigh a lot. wheels are physically linked, the beam can be set into oscillation if one wheel hits a bump and the other doesn't.
FRONT SUSPENSION - INDEPENDENT SYSTEMS
So-named because the front wheel's suspension systems are independent of each other (except where joined by an anti-roll bar)
MACPHERSON STRUT OR MCPHERSON STRUT
This is currently, without doubt, the most widely used front suspension system in cars. The system basically comprises of a strut-type spring and shock absorber combo, which pivots on a ball joint on the single, lower arm. At the top end there is a needle roller bearing on some more sophisticated systems. The strut itself is the load-bearing member in this assembly, with the spring and shock absorber merely performing their duty as oppose to actually holding the car up. The steering gear is either connected directly to the lower shock absorber housing, or to an arm from the front or back of the spindle (in this case). When you steer, it physically twists the strut and shock absorber housing (and consequently the spring) to turn the wheel.
DOUBLE WISHBONE SUSPENSION SYSTEMS.
The following three examples are all
variations on the same theme.
COIL SPRING TYPE 1
This is a type of double-A or double wishbone suspension. The wheel spindles are supported by an upper and lower 'A' shaped arm. In this type, the lower arm carries most of the load. If you look head-on at this type of system, what you'll find is that it's a very parallelogram system that allows the spindles to travel vertically up and down. When they do this, they also have a slight side-to-side motion caused by the arc that the wishbones describe around their pivot points. This side-to-side motion is known as scrub. Unless the links are infinitely long the scrub motion is always present.
COIL SPRING TYPE 2
This is also a type of double-A arm suspension although the lower arm in these systems can sometimes be replaced with a single solid arm (as in my picture). This transfers the load-bearing capability of the suspension almost entirely to the upper arm and the spring mounts. The lower arm in this instance becomes a control arm.
MULTI-LINK SUSPENSION
This is the
latest incarnation of the double wishbone system described above. It's
currently being used in the Audi A8 and A4 amongst other cars. The basic
principle of it is the same, but instead of solid upper and lower wishbones,
each 'arm' of the wishbone is a separate item. These are joined at the top and
bottom of the spindle thus forming the wishbone shape. The super-weird thing
about this is that as the spindle turns for steering, it alters the geometry of
the suspension by torquing all four suspension arms. They have complex pivot
systems designed to allow this to happen.
Car manufacturers claim that this system gives even better road-holding
properties, because all the various joints make the suspension almost
infinitely adjustable.
TRAILING-ARM SUSPENSION
The trailing arm system is literally that - a shaped suspension arm is joined at the front to the chassis, allowing the rear to swing up and down. Pairs of these become twin-trailing-arm systems and work on exactly the same principle as the double wishbones in the systems. The difference is that instead of the arms sticking out from the side of the chassis, they travel back parallel to it. This is an older system not used so much any more because of the space it takes up, but it doesn't suffer from the side-to-side scrubbing problem of double wishbone systems.
TWIN I-BEAM SUSPENSION
a combination of trailing arm suspension and solid beam axle suspension. Only in this case the beam is split in two and mounted offset from the centre of the chassis, one section for each side of the suspension. The trailing arms are actually (technically) leading arms and the steering gear is mounted in front of the suspension setup. Ford claim this makes for a heavy-duty independent front suspension setup capable of handling the loads associated with their trucks.
TRANSVERSE LEAF-SPRING
This system is a bit odd in that it combines independent double wishbone suspension with a leaf spring like you'd normally find on the rear suspension. Famously used on the Corvette, it involves one leaf spring mounted across the vehicle, connected at each end to the lower wishbone.
REAR SUSPENSION - DEPENDENT (LINKED) SYSTEMS
SOLID-AXLE, LEAF-SPRING
It is simple and cheap to build. The ride quality is decidedly questionable though. The drive axle is clamped to the leaf springs and the shock absorbers normally bolt directly to the axle. The ends of the leaf springs are attached directly to the chassis, as are the tops of the shock absorbers.
SOLID-AXLE, COIL-SPRING
Because the leaf springs have been removed, the axle now needs to have lateral support from a pair control arms. The front ends of these are attached to the chassis, the rear ends to the axle.
BEAM AXLE
This system is used in front wheel drive cars, where the rear axle isn't driven. (hence it's full description as a "dead beam"). Again, it is a relatively simple system. The beam runs across under the car with the wheels attached to either end of it. Spring / shock units or struts are bolted to both end and seat up into suspension wells in the car body or chassis.
4-BAR
4-bar
suspension can be used on the front and rear of vehicles.
