Car Suspension System - Functions And Components

One thing every body wants from a car is comfort. In any automobile, the comfort it can delivery is greatly tied to its suspension system. Without a suspension system no body will opt for a ride in any car, no matter how luxurious it may appear. How is that so? In this article we shall look at the function of the suspension of any car and the basic component of the suspension system.

Function of Suspension

Apart from your car's tyres and seats, the suspension is the prime mechanism that separates your bum ( seated back side) from the road. It also prevents your car from shaking itself to pieces. No matter how smooth you think the road is, it's a bad, bad place to propel over a ton of metal at high speed. So we rely upon suspension. People who travel on underground trains wish that those vehicles relied on suspension too, but they don't and that's why the ride is so harsh. Actually it's harsh because underground trains have no lateral suspension to speak of. So as the rails deviate side-to-side slightly, so does the entire train, and it's passengers. In a car, the rubber in your tyre helps with this little problem, while all the other suspension parts do the rest.

Component of the Suspension

In it's most basic form, suspension consists of two basic components:

Springs

These come in three types. They are

• coil springs, 

• torsion bars and 

• leaf springs. 

 Coil springs are what most people are familiar with, and are actually coiled torsion bars. Leaf springs are what you would find on most American cars up to about 1985 and almost all heavy duty vehicles. They look like layers of metal connected to the axle. The layers are called leaves, hence leaf-spring. The torsion bar on its own is a bizarre little contraption which gives coiled-spring-like performance based on the twisting properties of a steel bar. It's used in the suspension of VW Beetles and Karmann Ghias, air-cooled Porsches (356 and 911 until 1989 when they went to springs), and the rear suspension of Peugeot 205s amongst other cars. Instead of having a coiled spring, the axle is attached to one end of a steel shaft. The other end is slotted into a tube and held there by splines. As the suspension moves, it twists the shaft along it's length, which in turn resist. Now image that same shaft but instead of being straight, it's coiled up. As you press on the top of the coil, you're actually inducing a twisting in the shaft, all the way down the coil. I know it's hard to visualise, but believe me, that's what is happening. There's a whole section further down the page specifically on torsion bars and progressive springs.

Shock absorbers

These dampen the vertical motion induced by driving your car along a rough surface and so should technically be referred to by their proper name - dampers. If your car only had springs, it would boat and wallow along the road until you got physically sick and had to get out. It would be a travelling deathtrap until the incessant vibration caused it to fall apart.

Shock absorbers (dampers) perform two functions. As mentioned above, they absorb any larger-than-average bumps in the road so that the upward velocity of the wheel over the bump isn't transmitted to the car chassis. But secondly, they keep the suspension at as full a travel as possible for the given road conditions - they keep your wheels planted on the road.

You want more technical terms? Technically they are velocity-sensitive hydraulic damping devices - in other words, the faster they move, the more resistance there is to that movement. They work in conjunction with the springs. The spring allows the wheel to follow the road, moving up and down. The kinetic energy of that moving unsprung mass is transmitted to the damper where it is dissipated. The damper does this by forcing gas or oil through a constriction valve (a small hole). Adjustable shock absorbers allow you to change the size of this constriction, and thus control the rate of damping. The smaller the constriction, the stiffer the suspension. Phew!....and you thought they just leaked oil didn't you?

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