The types of suspension in common use not only differ from car to car, but also from the front to rear axles. All modern cars are fitted with Independent Front Suspension (IFS). This means that both front wheels are free to move up and down, independently of each other. This is especially important for the front wheels, as bumps in the road will inevitably affect the steering. To keep this to a minimum, the independent suspension system ensures that the action of one wheel does not affect the other.
There are four basic advantages of the independent front suspension system:
1) Improved steering precision because the wheel movements are not linked from side to side. There is reduced gyroscopic reaction, and the wheel travel path is more accurately controlled.
2) Better road-holding through the use of softer springs and wider spring-base, aided by reduced unsprung weight.
3) Increased ride comfort because of the softer springs and reduced unsprung weight. Coil springs and torsion bars are used for suspension purposes only, while radius arms and torque bars locate the axle units.
4) Increased passenger accommodation arising from the ability to position the engine further forward and lower, owing to the removal of the solid axle beam that required clearance for its vertical movements. A lower bonnet line is also obtainable.
The majority of IFS advantages can be applied to Independent Rear Suspension (IRS), but the reduction in unsprung weight of the rear axle by about 50 per cent is especially important to the improvements in ride comfort, road-holding and traction. Passenger space is further increased by the absence of propeller shaft and final drive assembly requiring body clearance for their vertical movements with the suspension action.