What is the difference between springs, dampers and anti-roll bars?
The spring carries the weight, the damper controls how the spring moves, and the anti-roll bar connects the two sides. Three separate jobs, constantly confused — particularly the damper, which almost everyone calls a shock absorber and which absorbs very little shock.
Springs. Support the vehicle's weight and allow the wheel to move over bumps without the body following. Their rate — how much force per unit of compression — determines how much the car moves for a given input. Stiffer springs reduce body movement and transmit more to the occupants.
Types include coil springs, leaf springs on many commercial vehicles, torsion bars, and air springs, which allow ride height and rate to be varied.
A spring alone is useless. Compress it and it stores energy, then releases it — the car would bounce repeatedly after every bump, since nothing dissipates that energy.
Dampers. This is where the energy goes. A damper forces hydraulic fluid through small orifices, converting the spring's oscillation into heat. Its job is to control the rate at which the suspension moves, not to absorb the impact — which is why "shock absorber" is a misnomer.
Most have different characteristics in bump (compressing) and rebound (extending), and adjustable dampers let those be tuned. Worn dampers cause a floating ride, poor body control and — importantly — longer braking distances, because a wheel that is bouncing is intermittently unloaded.
Anti-roll bars (sway bars). A torsion spring connecting left and right suspension. When both wheels move together it does nothing. When one side compresses more than the other — which is what happens in a corner — the bar twists and resists, reducing body roll.
Its other use is a tuning tool: stiffening the bar at one end changes the balance between understeer and oversteer, which is why suspension setups adjust them.
Bushes and mounts locate everything and absorb vibration, and perished bushes cause vague handling and knocking noises attributed to dampers.
The compromise: comfort wants soft springs and long travel; handling wants control and minimal movement. Every road car is a negotiation between the two.