TYRES

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Tyres

Let us look at one of the most important and at the some time most neglected item on most motor vehicle, tyres.

Most drivers occasionally check pressures with a quick look and a kick, and never really think about the important function of those four circular pieces of rubber, whose area of contact with the road surface at any moment when rotating is about the size of a size ten (10) shoe.

Tread Pattern

Contrary to popular belief the groves or channels in the tyres are not for the purpose of traction.

The sole purpose of the groves or channels in the tyres is to remove water from the road surface

The Function of the Tread Pattern.

When the tyres are rotating the groves or channels are designed to pick up the water at the leading front edge of the tyre and channel that water and force it to pass to the rear and sides of the tyre, enabling the rubber to remain in firm contact with the road surface.

At sixty miles per hour a tyre has to shift gallons of water every second if the rubber is to bite down onto the road surface.

The deeper the groves or channels in the tread pattern the easier the tyres can carry out this function.

As the tyres become worn through use, the groves become smaller and smaller reducing, and sometimes completely eliminating the tyres ability to remove the surface water leading to a very dangerous condition known as Aquaplaning.

When the rubber can not bite down to the road surface in wet weather, either because the channels are not deep enough or you are traveling to fast for the conditions, the tyres start to skim along the surface of the water and lose contact with the road surface.

Now you will be in real trouble because when you brake the vehicle, the road wheels stop rotating immediately but the vehicle continues to move forward at the same speed,

The rubber is not in contact with the road surface so therefore cannot retard the vehicle).

When the vehicle is steered into a corner the angle of the front wheels change but the vehicle will not change direction. (The tyre is not in contact with the road surface so the rubber can not change the direction of the vehicle).

At this point your vehicle is really behaving just like a speed boat on the water.

Aquaplaning (how to reduce the risk)

• In wet weather reduce your road speed.

• Never use tyres that are below the legal limit for your type of vehicle.

• Keep tyres properly inflated.

Minimum Tyre tread depth for Saint Lucia

Type of Vehicle
Minimum depth in Millimeters

Car/Jeeps (Small) 1.mm

Jeeps (Large) 2.mm

14 Seat Passenger Bus 2.mm


Please remember these limits are the legal minimum depth of the channels for your type of vehicle, and anyone with an eye for safety will think about replacement when the rubber is down to around the 3mm mark.

Prepared by
Martin P. Joseph
Driving Examiner