SHOCK-ABSORBING TYRES.

Northern Advocate, 12 June 1926, Page 12

SHOCK-ABSORBING TYRES.

THE SERVICE OP R ÜBBER. MUCH DEPENDS ON ROADS. In all motor tyres rubber forms at least part of a device whose chief function is to absorb shocks. This fact, coupled with the common knowledge that rubber is a good shock absorber under any circumstances, naturally leads to the idea that the rubber portion of a pneumatic tyro plays a larger part in the shockabsorbing action of the tyre than it really does. In the case of a solid tyre the rubber docs not compress very much, even under heavy load and groat shock, the quality and hardness of rubber necessary for tyre construction being such that the compressibility of the tyre is very small. If a thick solid-rubber tyre compresses only slightly, it is obvious that the thin tube and comparatively thin cover of a pneumatic tyre will bo comprehensible by quite a small amount, and the shock-absorbing powers of the rubber due to its compressibility will bo negligible.

The chief reason why rubber is so necessary at the present time for tyre manufacture is that it is the most suitable material for the purpose, on account of its being, when in normal condition, airproof and waterproof, fairly strong, very flexible, a good gripping medium, and adaptable to I manufacturing processes. Its chief functions in a pneumatic tyre are to contain the air and to stand rapid and almost continual deflection without becoming permanently deformed or stretched, to be unaffected by moisture under normal conditions, and to give a good grip on the road. These properties are not easily found combined in any one other material, and it is because of them that rubber is chiefly used for pneumatic tyres, and not because of its own shock-absorb-ing qualities. Practically all of the shock-absorbing qualities of a pneumatic tyre depend upon the way in which the air is used. TYRE PRESSURE A FACTOR. The whole value of a tyre as a shock-absorber depends upon, the amount of compression that will take place under a given load. Increasing the air pressure will make the tyre less resilient, undoubtedly, but the tyre’s useful range of efficiency as an i absorber of severe shocks will be in- i creased. Although the light shocks many out be so well absorbed, the heavier shocks, more in need of atten- j tion, will be more thoroughly ob- ] sorbed. Tyre pumping pressures must 1 be dictated by individual require- j ments, however; no hard and fast j rules can bo laid down. On good roads pressures may vary between j quite wide Imits, with satisfactory | results. With fairly uniform but mod- j erately rough roads, having no severe j stretches, probably the lower pressure would be the more suitable; whilst for running on roads having a fair amount of really hard surface, the higher pressures would seem most suitable. In deciding on tyre pressures, consideration must be given to the vari--j ous factors which influence tyre effi- ■ ciency, including load, running condi- ! tions, tyre size, etc., if the best re- j suits are to be obtained. i

USEFUL TOOLS. It is seldom that the medium price car is sold with more than bare necessaries in the tool kit. A pump, jack, spanners, and screw drivers are provided with even the cheapest ear, and for the driver who never ventures to make anything but the simplest adjustments this equipment is> adequate. A motorist who wishes to add to his' mechanical knowledge and effect small economies enu do so by expenditure on

a few special tools. A wheel-puller is a handy garage tool, it makes brake repairs and axle adjustment possible. A valve spring remover is a necessity to the motorist who undertakes valve grinding or decai-bonising. In this

connection a tappet gauge is valuable for re-setting clearances. A contactbreaker file is useful for remedying ignition troubles, while a sparking-plug tester enables faults to be readily located. The driver who finds it inconvenient to attend the battery service station should carry a hydrometer. A few well-chosen tools are a justifiable extravagance.

JOTTINGS. A London coroner recently remarked that many accidents to aged and infirm people would not occur if drivers treated them as if they were young children. * * * * j Over half of the cars put on the j road in America during 1925 were ( fitted with totally enclosed coach- I work. | *** • j Never open the throttle suddenly, j or have it open very far when the ear j is standing. Racing the engine like this is very injurious, more so when the engine is cold. More engines have been ruined by racing while idle than have been worn out in actual driving under a load.

It is announced by the Dunlop Rubber Company that their world famed annual road race from Warrnambool to Melbourne (105 miles) will be held mi Saturday, October 9, that date having been allotted by the League of Victorian Wheelmen for this classic road event. As in previous years In-ter-State and New Zealand test race will be held to decide the respective accredited representatives for the “Warrnambool.”