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The Success of the Pneugrippa Tyre-cutting Process

16th August 1935, Page 51
16th August 1935
Page 51
Page 51, 16th August 1935 — The Success of the Pneugrippa Tyre-cutting Process
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Keywords : Tires, Tread, Slick Tyre

THE interesting method of giving tyres a better grip on the road by making equally spaced shallow cuts across the treads, which is employed in the Pneugrippa Adersol process, has been developed in this country by Tecalemit, Ltd., Great West Road, Brentford. This cutting process has been tried out with most satisfactory results on one of our staff cars on which the tyre treads had worn to such an. extent that the non-skid pattern was only just visible. The treatment has given a definite sense of security, which would be quite abSent if the treads had worn smooth, and there is a marked freedom from wheel-lock or Side-slip when the brake is applied.

Recently, a French engineer, writing. in La Vie Automobile, gave a résumé of the progress. made with the Adersol treatment, and the reasons for its success: It is pointed out that the adherence of a tyre depends chiefly on the sharp angles meeting the road. This explains the good adherence afforded by the grooves made by the Adersol system, since they provide the maximum number of sharp edges, the slots made by the saw being repeated about every in., and being radial.

Some people have suggested that the system might cause a tyre to wear out more rapidly. Actually, the slots are only about in. deep, and after a certain number of miles—usually between 3,000 and 6,000, depending upon the vehicle and driver—the new non-skid tread formed by the cuts disappears, whilst on a new tyre having a deep tread pattern the wear is not so easily observable, and this creates the above impression. Technically, the difference in wear between an ordinary By means of the Pneutyre and one cut might be grippa machine, which considered proportionate to forms slots about in. deep in the cover, safe volumes of rubber available tyre life can be consider ably extended, at low in the wearing treads, but in the cut tyre this is only some 5 per cent. less. In practice, however, the wearing life should be about equal, because the tyre can be used almost as far as the carcase without the loss of its non-skid properties, whilst the prevention of locking or spinning of the wheel avoids the tearing of rubber from the tread.

A Question of Durability.

If makers delivered smooth tyres presenting a larger wearing surface, they might last longer than those having a smaller area of non-skid tread, but it does not occur to anyone to complain, because the smooth tyre would not give the same security.

In the case of an official test made by a big transport company, tyres were changed because of their loss of the original non-skid tread after a distance of 40,000 miles, the wear then averaging a depth of 1i in., or approximately 1-50 in. in 600 miles, but the Adersol process enabled them to run a further 9,000 miles, and, curiously enough, the further wear then proceeded at the rate of only 1-50 in. per 1,160 miles, partly accounted for

by the larger surface of tread treated.

Tests carried out at Brooklands by Capt. Eyston showed that on a dry surface the slots, even on new tyres, reduced the stopping distance by 25 per cent., whilst on a wet surface the corresponding decrease was 45 per cent.

In the case of the transport company to which we have referred, a vehicle weighing 10 tons was driven at 22 m.p.h on a wet surface. With new and untreated tyres, it drew up in 32 ft., wheel locking and side skidding occurring; using old tyres having Adersol cuts, the vehicle, under the same conditions, stopped in 20 ft., without the wheels skidding or locking.

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People: Eyston

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