TIRE PRESSURES

Evening Post, Volume CXIX, Issue 98, 27 April 1935, Page 28

TIRE PRESSURES

CHECKING UP NECESSARY

The maintenance of the correct air pressure in tires is one of the simplest routine jobs on a car, yet it is one which is often neglected. To check and rectify the pressure of the tires occupies but a few minutes, and should be done regularly—at least. once a week. Neglect of tire pressures will affect the life of the tires, the safety of the car, and the riding comfort of the passengers. It is peculiar that, even when the valve and inner tube are in perfect order, a certain amount of air escapes gradually—a somewhat puzzling phenomenon. This is due to diffusion. Diffusion, it has been explained, is a physical process in which the oxygen in the compressed air, and, to a very much lesser extent, the nitrogen also, dissolves in the tube rubber and forms part of it; and as the content of these gases in the rubber increases, some quantity is given off on the outside of the tube, and losses due to diffusion take place. Un- | der normal conditions the amount of

air lost due to diffusion, in the case of motor-car tires, varies from lib to 31b per square inch each week. It is because of ; this . unavoidable loss of air that recommendations are made that tire pressures should be checked each week, and any loss made good.' One of the most important features of the tire is the metal valve through which the air is admitted, and which acts as a reliable seal to the air pressure. The type of valve in use today has an inside mechanism which constitutes the main air check. The valve cap is a second check. AMERICA BRIGHTENING UP The motor works of the United States turned out 340,000 new cars in February and projected turning out well over 400,000 in March. This means over 200,000 more new cars than in the corresponding period of last year, and nothing approaching these figures has been experienced by the industry since 1930. Naturally, there is a feeling of jubilation and confidence is returning that so far as the .motor manufacturing business is concerned the depression is well oh the retreat. About 60 per cent, of American cars now have six-cylinder engines. Nearly all the rest are of eight cylinders, the fours having practically disappeared, as also have the sixteens. Twelves are still being produced, hut their numbers are negligible. , Some experiments have been made by Scotland Yard in warning pedestrians and motorists, as they go along. A police car equipped with a loud speaker between the headlamps and a microphone into' which the constable could speak, has patrolled some of the roads in., the west of London. Speech is amplified considerably and in one instance the police called out to a driver ahead that he was "on the crown of the road, there is plenty ' of room to the left." In spite of the traffic noise this booming voice was heard by the offending driver, who swerved to the near side. On another occasion pedestrians who were attempting to cross the road against traffic lights were warned. Mr: Edward J. Thompson, of Worthing, Sussex, claims to- have been the first English chaffeur. He was employed for many years by the late Hon. Evelyn Henry Ellis, nephew of the 1 Duke of Portland, who introduced the ■ first petrol-driven car into England ! from France in June, 1895; This was • a 4 h.p. Panhard and Levassor.