TYRE TYPES DESCRIBED

Press, Volume CXII, Issue 33034, 29 September 1972, Page 13

TYRE TYPES DESCRIBED

Although there is an increasing awareness among New Zealand motorists about the need for tyre care in the interests of road safety, the various types of tyre now being offered in this country have inevitably led to some confusion in the minds of many motorists, particularly when they go shopping for replacement tyres, says Mr W. B. Deavoll, the sales administration manager for the Firestone company.

“While I would not want to be accused of talking down to the everyday motorist who, perhaps, lacks the sophisticated knowledge of the motoring enthusiast, I do feel that in the interests of his own pocket and, more important his own safety and that of his passengers, he should have a clear idea about the

relative merits of the various types of tyres available to him today," said Mr Deavoll.

The following glossary of tyre terms should be of some value in this, he said. Cross-ply or bias-plyt This is the basic type of tyre construction. "Bias’ means that the plies, or layers of fabric cord, are applied in a criss-cross fashion from rim-edge to rim-edge. A bias tyre can be made with two or four plies of textile. Belted bias: Basically, the belted-bias tyre is an extention of the bias-ply. Beginning with the same construction as the bias, reinforcing belts which encircle the circumference of the tyre are added before the tread is applied. The belts make the tyre more resistant to punctures, cuts and bruises. Belted-bias tyres are more expensive than conventional tyres, because of the additional materials and labour.

Radial: This type of tyre has a body made of cords

running straight up and over in a “hoop” fashion from rim-edge to rim-edge. To give puncture resistance, long life and tread stability, two of the four reinforcing belts run round the tyre’s circumference under the tread. Radials give a firmer ride at low speeds and an exceptionally smooth one at medium and higher speeds.

Because the manufacturing process is more complicated. these tyres cost more than conventional or beltedbias tyres. Because the radial tyre provides better traction and higher cornering power than either the conventional or the belted-bias tyre, it should never be “mixed” with the other types.