A car suspension system is a combination of various components joined together to perform several tasks. The suspension system has following functions:
- It keeps the vehicle’s tires in contact with the ground at all times.
- It helps in controlling the motion of a vehicle
- It isolates the chassis and the occupants from the shocks that are encountered during traversing the rough terrains.
There are several types of suspensions available as per their applications, but in general they all perform the action of controlling the vehicle movements sideways, forward/backwards and in up/down direction.
This function is accomplished by a set of components connected together with the help of links and rods. following are the main components of a suspension system:
Tire is the first component that establish the contact with the ground. There are several specification of tires available in market depending upon the applications like dry surface, wet surface, rough roads, all terrain etc. The main portion of a tire that ensures proper grip and handling is Contact patch. More the contact patch more will be the grip.
Wheel is the component on which the tire is mounted. There are several types of wheels available depending upon the Diameter, width and material. It can be a steel wheel or an alloy wheel.
Apart from the diameter and width, Offset is an important aspect in wheel design. It is generally indicated as positive/higher or negative/lower offset. Negative offset is when the mounting face is away from the wheel center line towards the outer edge of wheel. Positive offset is when the mounting face is away from the wheel center line towards the inner edge of wheel.
It is critical in the designing of the knuckle of suspension as it defines the scrub radius.
Brake rotor is a disc that is fitted over wheel hub. Brake rotor is place in between wheel hub and wheel. It may be slotted, plain or grooved for quick heat dissipation. Brake caliper is attached to it which houses brakes in it and helps to stop the vehicle.
Wheel hub is the component on which wheel mounts. It has studs attached to it in case of nut over stud configuration and threaded holes in case of lug nut configuration. Wheel hub provides the adequate contact surface for the attachment of wheel. The wheel hub is press fitted to the knuckle of the suspension.
Knuckle or upright:
Knuckle is the component that has the major role in the suspension. Suspension arms, steering rods, wheel hub, brake bracket and shock absorber are mounted on knuckle. Alignment of knuckle define several angles like camber, caster, toe, king-pin\steering axis etc. which plays a major role in suspension design. Knuckle houses a bearing in its center that has a splined axle passing through it. This bearing is press fitted into the knuckle.
Shock absorber and damper:
Shock absorber and damper are used to absorb the shocks encountered during an uneven ride and damp it so as to isolate the shocks from the chassis and occupants. One end of shock absorber is connected to knuckle and another is connected to chassis.
Brake caliper is a part an assembly that consists of piston, brake caliper bracket, brake pads, sliding pins, nuts, dust boots and washers. This complete system works together to stop the vehicle.
This system is attached to the brake rotor with a very minute gap between the brake pads and brake rotor and on other side it is attached to knuckle.
Steering tie rod:
Steering tie rod is the link between the steering rack and the knuckle. To every motion of steering rack, the tie rod transfer the motion to the knuckle which in turn rotate the wheel about the steering axis.
Suspension Arm or control arm:
Control arm are the vital part of a suspension system. It connects the knuckle to the chassis and hence controls the up/down motion of suspension system. The swinging action of the suspension in a controlled manner is accomplished by the control arm. One point is connected to the knuckle via a rod end having spherical bushing and another end is connected to chassis via two rubber bushings.
The designing of each and individual component is critical from the strength point of view. A special care is taken during component level designing, considering all the loading conditions.