Care for tyres as they are important for your safety

Bridgestone's "think before you drive" campaign over the past few months has involved getting to know about that most critical of safety items on a car: the tyre.

Bridgestone's "think before you drive" campaign over the past few months has involved getting to know about that most critical of safety items on a car: the tyre.

Whether it is the inner liner and sidewalls or the beads used on construction of a tyre, there is plenty to it than meets the eye.

Most car users and motorists know the brand name of a tyre and something called the tread area.

The tread area is what usually gets checked at police road blocks as a certain minimum tread has to be maintained for the car to be considered legal and roadworthy.

When the tread wears down considerably past the point that would be considered legal, it's time to change the tyre or else risk the long arm of the law or worse - tyre failure while driving.

The tread area is where the proverbial rubber meets the road - it is the part of a tyre that makes contact with the road surface, transferring power from the motor for forward motion or stopping power from the brakes that allow the vehicle to come to a halt or be slowed down.

The tread plays many roles in the functioning of a tyre in that it creates the changes in direction as required, disperses water in wet and rainy conditions and is basically your first defence against potential damage from stones, obstacles, debris on road surfaces, potholes, speed humps or anything lying in its path.

Because it is the only point of contact between the car and road, the tread is often referred to as the footprint. The footprint varies according to the tyre size and in some cases it has been compared to the size of a man's hand, while others have described the four-tyre tread areas as being no bigger than four sheets of A4 paper.

However one looks at it, these four-tread areas or patches or contact points keep the car on the road, offering traction and grip, directional stability and cushioning.

It is these four contact points of the tyres that allow the vehicle to move, stop, turn, switch direction - and all with relative comfort and ease.

What this means is that tyre manufacturers have many things to consider when designing a tyre, from safety to performance, wear and tear.

It sounds silly, but one of the first things to consider in tyre design is just what its main use will be.

Of course, we know it is to be fitted on to a vehicle which will in turn be driven by its driver, possibly carrying occupants, moving at a combination of high and low speeds.

But when it comes to the general use of the tyre, the designer needs to look at a number of elements that include designing the actual tread to suit the purposes for which the tyre will be used.

Designers will consider things like ride quality and noise, ensuring that there is enough grip for wet or dry conditions, that the tyre performance suits the speed range of the vehicle, and that there is enough ability on the tyre to disperse water, have a fairly decent wear life and have a high resistance to damage.

There is certainly a lot of expectation from the tyre, particularly because the tread directly impacts on the way the car will respond to whatever input the driver makes.

The reaction of a tyre to the various inputs of the driver is critical to whether a tyre will be accepted in the market or not.

On the average family sedan, one expects the tyre to be responsive, smooth and not jittery or skittish.

An ultra-high performance tyre may be so responsive and direct in its reaction to driver input that it may be considered nervous on conventional driving and road conditions.

In the normal driving of a sedan, this tyre may actually be tiring on a daily basis, but for the kind of driver who is experienced enough to "read" what a car and tyres are doing in the varying road surfaces, this high performance and the acute feedback would be welcome.

This does not mean that it should be put onto a conventional sedan, however, just as one does not expect to put racing tyres on a road-going car and expect it to be effective.

Just like one gets different kinds of shoes for walking, jogging, exercising, gala dinner, smart or casual affairs, tyres also have their various purposes and it is this that designers have to consider when creating a tyre which will do its best for the market and conditions it is intended for.

When it comes to the durability, life cycle and performance of the tyre tread, much emphasis is placed on the actual compounds or materials that are used to make up the tyre and its tread.

There is still no getting away from the importance of the design, however, and this particularly affects the lifespan of the tyre itself.

When it comes to determining the needs for so-called general use tyres, the issue of a quiet ride keeps popping up.

It's especially important in a world that is heavily polluted and looking for ways to cut down on noise and gas emissions from cars.

Think about it the next time you hear a car pass you by - the majority of the noise you hear is actually the feedback from the tyre meeting the road surface.

This noise is actually caused by air flowing through the grooves of the tyre as well as the tread lug and ribbing that brushes against the road surface to create a noise.

Remember that a tyre is dynamic and moves and changes shape before recoiling to its original shape when the tread meets the road.

Those same centrifugal forces that affect the shape of the tyre affect the tread as well - when each lug or part of the tread meets the road, it alters in shape and angle.

The tread area of the tyre has to resist all these stress factors and forces and maintain its footprint contact with the road.

The diagram of a general use tyre on this page illustrates the many separate blocks and grooves that are part of the tread area.

The tread is able to keep its shape and strength - despite all the other goings-on happening in the tyre - thanks to special stabiliser belts.

Notice the two outer tyres, and how they are deforming under the stress of medium to high speed cornering.

Even under stress though, the tyre works in a way that allows the footprint to be maintained and the car to stay on course.