They are arguably the most essential safety item on a vehicle

Morgan Naidu

Morgan Naidu

There are many elements to Bridgestone's Think Before You Drive campaign, but perhaps the most critical is that it gets motorists to better their understanding and appreciation of the tyre - arguably the most essential safety item on a vehicle.

Over the past few months we have delved into areas of tyre construction, reinforcement, sidewalls, inner linings and tread patterns or footprints - all with the purpose of understanding in intimate detail just what it is exactly that tyres do for us.

Tyres are but four items of a car that has over a million parts, components, devices and design elements. Yet, all of these are rendered impotent if the car has no tyres or non-functioning tyres.

The tread or footprint of the tyre is critical in that it must maintain its shape irrespective of the conditions or duress it undergoes. This keeping of its shape is what allows the tyre overall to react or respond whatever input the driver makes.

It is this tread that can be rendered in any number of patterns, depending on the specific driving conditions or performance for which it has been built.

Previously, we touched on the various tyre tread options which ranged from the sports tyre to the high-performance tyre and the more compromising general use tyre as typified by most modern-day saloon or hatchback car tyres.

The general purpose tyres are intrinsically linked to the everyday cars - the sedans, hatches or any vehicle that would be considered conventional rather than specialist.

These vehicles - and invariably the general use tyres fixed to them - are used daily for a combination of private and business use with the users expecting minimum fuss, maximum performance and reliability.

No one wants the inconvenience of a breakdown, engine failure, starter problem or such, and tyres are no different. Yet, the tyres are very often the most disregarded parts of a car.

Who actually takes the time to look at the tyres and consider the makes, the brands, the sizes, rating and intended uses?

When problems occur, however, most car owners are likely to change tyre brands altogether, subscribing to some false sense of security that a new brand name means no problems whatsoever.

This is what makes the general use tyre so unique. It has many applications and the burden of expectation on it is indeed great. Not so the specialist 4x4 or racing sports tyres - these have specific uses and expectations, therefore there is a greater degree of tolerance and understanding from the end user.

An off-road tyre may be noisy on the tar, yet perform fabulously in off-road conditions; a high-performance tyre may give a harsh and unyielding ride, yet its ability to grip the corners outweighs any discomfort.

This is because the mindsets of the drivers of these cars with specialist tyres are different.

The general use tyre, however, creates somewhat of a headache for the designers, given the unfortunate ignorance of many end users or purchasers.


Having seen the involved construction of tyre sidewalls and the importance of the tread's shape retention, it is critical to understand the interaction between the two.

The sidewall contributes to the tread's ability to keep its shape in constantly changing road conditions and surfaces.

In retaining shape, it means that both components must strongly resist any deformation - however severe the stress.

The footprint is also maintained with the strategic intervention of stabiliser belts placed underneath the tyre tread. Stabiliser belts are the silent heroes of tyres and help improve performance and durability of a tyre.

Remember that it's not the rigidity of the sidewall that does most impact but its ability to deflect the lateral forces when a tyre is in motion.

That ability to continue moving when the tyre is in motion is sometimes referred to as inertia, and it is this that maintains that momentum even when the driver changes input on the steering wheel and heads off in an intended direction.

Coming up to a corner, the weight of the vehicle pushes it forward and towards the outside of the corner as the inertia puts higher force when the corner sharpens.

This in turn creates additional load on the outside of the turning tyre and to the other tyre on that side of the vehicle. This load forces the tyre down on to the road while the vehicle's weight is already pushing towards the outside of the corner.

These two actions result in a downward compression of the sidewall and the vehicle's weight causes the sidewall to bend.

The sidewall part of the tyre attached to the tread bends inwards and the part near the tyre beads bends outwards as the force of the weight is extended.