Understanding Car Suspension Systems: Types & Components
Conventional Suspension Systems
Mission: To minimize the impact of terrain irregularities on the vehicle body.
Types of Suspension:
- Independent: When one wheel moves, it does not affect the other.
- Dependent (Rigid): Movement of one wheel directly affects the other.
Components:
- Elastic Elements
- Shock Absorbers
- Linkages
- Stabilizer Bar
- Suspension Arms
Elastic Elements:
Springs: Helical coiled steel rods. (Variations include springs with closer turns and truncated springs.)
Features:
- Wire diameter: Thickness of the spring rod.
- Spring length: The overall height (H).
- Spring width: (W).
- Spring shape: Consistency in form and number of turns.
Checks:
- Breaks: Visual inspection.
- Elasticity (Assembled): Check for loss of strength by observing wheel behavior, shock absorber function, and ride height.
- Elasticity (Disassembled): Compare measurements against the manufacturer’s specifications (with and without a defined weight).
Leaf Springs: Bent or flat rectangular steel bars.
Checks:
- Breaking and dirt: Visual inspection.
- Wear: Assess elasticity by observing ride height. Check for bumpy and stiff shocks. Further inspection involves disassembling and measuring the distance of the spring’s arch.
*Note: Leaf springs always require shock absorbers.*
Torsion Bar: One or two steel bars that resist twisting forces to counteract weight.
Checks:
- Breaks, dirt, and wear: Visual inspection.
- Check ride height, as it is affected by the torsion bar, wheels, and shock absorbers.
Shock Absorbers:
Responsible for absorbing terrain irregularities and body oscillations.
- Simple: Damping in only one direction (e.g., braking).
- Double-acting: Damping in two directions.
- Gas (combined): When compressed, it slowly returns, pushing hydraulic oil. Loss of gas results in it functioning like a conventional hydraulic shock absorber.
- Hydraulic: When compressed, it does not return on its own.
Suspension Arms (Control Arms):
Allow for the wheel’s vertical movement. They are typically triangular, fitted with silentblocks at each end, connecting the chassis or subframe to the wheel hub or directly to the damper. They can be longitudinal or transverse.
Checks:
- Most importantly, check for serious strains that could affect steering alignment.
- Check for breaks and excessive dirt, which can render them nonfunctional.
Stabilizer Bar:
Made of elastic material. It doesn’t function when the vehicle is traveling straight. During cornering, it counteracts body roll by transferring weight from one side to the other, enhancing stability. It can be located at the front or rear, but is most commonly found at the front.
Checks:
- Check for breakage or deformation, which can alter steering dimensions if the arm is clamped. However, if the shock absorber is affected, it will not vary.
Linkages:
Transmit motion from one component to another, but are not a fixed joint.
Silentblock:
Metal and rubber bushings that reduce wear, noise, and vibration during movement.
Checks:
- Check for cracks.
Dependent vs. Independent Suspension:
Dependent (Rigid) Suspension: When one wheel encounters a bump, the connected wheel on the opposite side is also affected because they are linked by a rigid axle.
Independent Suspension: When one wheel encounters an obstacle, the other wheel is not affected.