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What Bits Keep Me on the Road?

What does keep a car on the road?

When you have a one-to-two tonne large metal object travelling down a road at speed, what are the bits that enable the car to remain in control and in contact with the road?  Yes, the driver is able to steer the car in the right direction when guiding the vehicle via the steering mechanism and the steering wheel, but there are other very important components in a car’s suspension that work in unison to hold the car on the road and keep the ride comfortable.

A suspension on a car is hugely important in that it separates the car’s occupants from the road and smooths out the ride over the bumps in the road.  A car’s springs absorb the bumps, and they come in three types: coil springs, torsion bars and leaf springs.

Shock absorbers (or dampers) have two main functions.  They also work to absorb any big bumps in the road so the speed at which the upward direction of the wheel over the bump is absorbed or slowed down.  Shock absorbers also push the wheel back down onto the road to keep the wheel planted on the road for maximum grip.  Shock absorbers also have plenty of upward and downward travel to ride the wheel up and over bumps or drop the wheels down into holes.

Also an integral part of the suspension, are the rubber grommets which separate a lot of the parts of your suspension from each other.  Obviously, they also hold components together and thus the rubber grommets link an A-Arm with the sub-frame or are used on anti-roll bar links and mountings for example.  The harder the material make-up of the bushes, then the harder the ride becomes for the occupants in the cabin.

Suspension types are mainly grouped as being dependent and independent.  However, even independent systems are typically joined across the car by an anti-roll bar and so are not truly independent.  Independent suspensions are named because their same axle wheel’s suspension systems are independent of each other.

A hydrolastic suspension is a suspension system where the front and rear suspension systems are connected together in order to keep the car level when driving over bumps.  The front and rear suspension units have hydrolastic displacers, one unit per side.  A hydrolastic suspension provides a nice soft ride, and the hydrogas suspension is an evolution of the hydrolastic suspension.  The Hydropneumatic suspension is a fabulous hydro-linked system used by Citroen where the suspension includes the brakes and steering as well as the suspension itself.  The fundamental technology of the Hydropneumatic suspension is hydraulics.  The fluid’s interaction with a pressurised gas creates a superbly smooth ride.

A well set up air suspension system can better the mechanised metal spring suspension in most situations.  As found in the new BMW cars, the luxurious, smooth and supple ride is superior.  It’s also found in large logistics trucks.

With the advent of computer-controlled suspension systems, the anti-roll bar is no longer needed.  The computerised system uses sensors to rapidly adapt a car’s suspension to changing road surfaces.  Ride height sensors and self-levelling systems mated to the suspension componentry also works to keep the suspension taut and the body roll to a minimum in the corners.

Next time you’re in your car, I’ll bet you’ll be thinking a little more about what the suspension is doing in conjunction with your tyres to keep you on the road.  Remember though, the safest way to stay on the road is to keep your speed appropriate to the road conditions.

You might like to shed some more light on the subject.  I know that Audi even uses a Magnetic fluid in some of their cars to create a good ride.

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