TYRE CONSTRUCTION.

Auckland Star, Volume LVI, Issue 184, 6 August 1925, Page 10 (Supplement)

TYRE CONSTRUCTION.

VOGUE OP THE BALLOON. UNIVERSALLY ADOPTED. A radical change in the principle of tyre construction was one of the features of the motor industry during the past twelve months- A low pressure tyre designed to give a greater degree of comfort in riding was introduced in the place of the high pressure several years ago in America, but its adoption was comparatively slow, owing to the various prejudices. Now, however, the low pressure tyre, or balloon as it is known, has been universally adopted, and it is part of the equipment of practically all makes of cars imported to these shores'. Even English manufacturers, who, with their traditional conservativeness, were reluctant to follow the fashion, are now equipping their cars with the low pressure type. . A further instance of its success is its adoption to moto? cycles. Balloon appropriately describes the appearance, of the new product. u>r in comparison with the old article, tinmodern one is surprisingly large. It idesigned on the oTersh.ing principle, having a greater cross ficctional area, that is from bead to the outside of the tread, than the liig.i prc--ure. The walls are thinner, and the inside tube is oniv lightly inflated These three diversions from the old principle allow the tyre on striking an object, to tr.kc the force of the blow, and it is correspondingly on the chassis, thus ensuring easy riding. For instance, on running over a stone the outside cover. which has considerable flexibility, on account of the cross section depth and the thinner walls compresses, and the tube with its light inflation, olfers no more resistance than a cush'on. Propensity to Puncture. One of the early prejudices against the Walloon was that it was more sus.-eptih'" to puncture. It was argued that "ueeause the balloon had a thinner carcase, it would more easily cut through. As a matter of fact the lower pressure allows balloons to- roll over and absorb objects that would puncture or rupture the highly Inflated tyre- The puncture contention also got sum.- support originally because the necesr-ity for keeping the tyre uniformly inflated was not sufficiently understood. Correct ; nfiation of the balloon, however, is a mo-t vital matter. Because they carry a very lowpressure to begin with, a drop of from five to ten pounds represents a big percentage of decrease in the total recommended presr-urc. And so running underinflated i-- just a- harmful to the balloon lyre- as it to drive, a car equipped with high pressure tyres a: inflations below those recommended for a normal load. Correct Inflation Essential. Owners of cars with ballojn tyres should never let the pressure drop more than 10 per cent below the recommended inflation for a normal load. For instance, if the recommended pressure is SO lb, the absolute minimum is 271b of air, below which the tyre is certain to suffer damage. The erroneous impression has got abroad, too. that the balloon tyre is not only built for comfort. Inn that it will stand rough u-age. and can he run over the worst kinds of roads, over railway tracks, that-'it can climb kerbs, and take without damage as well, the jolts and skid which follows slamming on tinbrakes while the car is maintaiuimi it high rate of speed. Properly cared for. balloon tyres will last as long and give mileage equal to that of high pressure tyres. It is remarkable how much abuse some balloons will stand, but the motorist should remember that every time he runs over a kerb or extremely rough road, he is gambling away mileage. Under correct operating conditions the balloon undoubtedly ensures greater comfort, less vibration, and better braking, and about equal mileage to that obtained from the higher inflated standard cord tyreGear Ratio Not Affected. The strictly balloon tyre requires a special rim, which, of course, with the new car. is now part .of the equipment, but a slight modification of the balloon known freely as the "semi-balloon." hut commercially as the "inter-chanaa-eable balloon," can be adopted to the rims of the older car. Experts were sceptical about the interchangeable balloon, which they said would have a detrimental effect on the gear ratio: against thi-s it is contended that the effect is negligible. Gear ratio, it is argued, is affected' only to the extent that the distance from the centre of the axle to the ground is increased by the inter-changeable .balloon tyre. But the inter-changeable balloon does not alter the distance from the ground because, being larger in cross -section, it flattens out under load, so that the car stands practically the same distance from the ground, as when equipped with the regular standard tyres.