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Don't Gamble With Tyres

11th February 1938, Page 107
11th February 1938
Page 107
Page 107, 11th February 1938 — Don't Gamble With Tyres
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Which of the following most accurately describes the problem?

on passenger vehicles Some of the Major Considerations to Which the Coach and Bus Operator Should Give Attention. The Advantages Offered by Low Pressure Equipment• THE operator of passenger-carrying

vehicles has to face an entirely different set of tyre problems from those which confront the user of goods vehicles. To the lorry owner the main features are " mileage" and "cost per mile." In his purchases he aims at obtaining the greatest number of miles per pound sterling, and all other considerations are secondary to that of value.

The coach proprietor cannot afford to overlook this question' of mileage, but a far more important consideration is (or should be) the safety and comfort of passengers. Reliability is also of great importance. To hold up passengers while a burst tyre is replaced is a most undignified business and often results in a loss of future custom.

o Security v.Mileage •

Long mileage and maximum safety do not necessarily go together. Safety from skidding is achieved by road grip, and where there is effective road grip there is friction, which causes the tyre to wear more rapidly.. This is inevitable, but it is well worth while to forgo that extra mileage in order to obtain complete security.

Bursts, too, can be dangerous, in addition to being • tronblesorrke. Coupled with skidding, they constitute the two chief dangers that a coach operator should try to avoid at all costs, for either is sufficient to do him considerable harm in the eyes of his patrons.

The obvious way to overcome both troubles is to buy only the best. A first-grade tyre is almost immune from bursts if properly treated, and it offers a tread design which is the result of long and patient research into the question of safety from skidding.

The basic idea of all anti-skid tread designs is to offer a good number of edges and corners to the direction of travel. It is these which give the grip. The tread blocks offer resistance to wear, but it is their extreme edges which bite into the road and keep the vehicle steady when the brakes are applied. Thus, tyres should be chosen which conform to these principles.

Most tyres incorporate a few circumferential ribs in ' their tread pattern and these are quite good to stop side-slipping. But they are useless to prevent forward slip, unless they be augmented with tread blocks which are well broken up. Nearly all first-class tyres embody these features, because the manufacturers have vast resources for research into all vital questions.

In the matter of comfort, the coach owner has a simpler task in tyre selection than the goods-vehicle operator, for the reason that he is not faced with the difficulty of choosing between high-pressure and lowpressure equipment. Obviously, there is only one choice—the .lowpressure tyre.

Tyres of this class can be obtained in different carrying capacities which enable them to deal with all weights. They are bigger than the corresponding high-pressure equipment and will thus accommodate a good volume of air at a moderate pressure. The carcase is more flexible and can be deflected considerably without damage.

• Low-pressure Merits •

As compared with the highpressure tyre, the low-pressure unit offers greater mileage, comfort and safety against skids, as well as being subject to less wear and tear, through the abience of vibration, on the chassis and bodywork. Accordingly, it is, in every way, a very desirable tyre.

Any coach which is fitted with high-pressure tyres is, in my opinion, out of date. The owner would not ask his patrons to sit on hard wooden benches. No, he provides them with luxuriously sprung, wellupholstered seats, and the comfort is often augmented by the installation of electric heaters and radio.

Why, then, should he ask them to ride on a class of tyre in which the pneumatic effect is not outstandingly apparent? If the vehicle be worth it, he should lose no time in converting to low-pressure equipment. This does not entail so great an expense as might be imagined.

When the present high-pressure tyres are worn out they can often be replaced by low-pressure equipment which fits the same rim. Even if new rims be necessary, the extra cost is trifling. New tyres have to be bought in any case, and the money might just as well be spent on the more modern equipment, the only additional expense being the wheels. Tyre distributors offer new wheels at approximately half normal price if these be bought with the cover and tube, i.e., as a unit,

• Standardize Equipment •

When replacing high-pressure with low-pressure equipment, the latter should never be fitted singly; that is, as the old tyres wear out one by one. Owing to the differences in height, etc., it is necessary to standardize the equipment. On a six-wheeled vehicle, for example, the two mostworn tyres could be replaced with low pressures which can be fitted to the front wheels..

When the next pair of original tyres wears out, these can also be replaced and the four low-pressure tyres can then be fitted at the rear. This leaves two high-pressures, which are transferred to the front until their working life is ended, when they can be replaced by the more modern tyres. Thus, the fitting of low-pressure tyres is accomplished by easy stages and big monetary outlay is avoided. Furthermore, it is quite unnecessary to scrap the original equipment until it has yielded its full mileage.

Above all, the operator should bear in mind that the tyres should be as reliable, from every point of view, as any other Dart of the vehicle. They, are an essential part of his service, part of his reputation, which he must do his utmost to safeguard. To take risks on cheap, faulty, or worn-out tyres is equivalent to gambling with his goodwill, and the life and limb of his

passengers. . V. B.

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