MOTOR NOTES

Bay of Plenty Beacon, Volume 1, Issue 38, 19 July 1939, Page 3

MOTOR NOTES

TYRE PRESSURES RISE AFTER RUNNING EFFECT OF TEMPERATURES Apropos lyre noises, there is the question of tyre pressures increasing owing to the rise in temperature whilst running. During the winter months, when the roads are so often wet and, have a pronounced cooling effect on the tyres, this is perhaps not very important, but in, dry weather the rise in tyre pressures can be sufficient to affect com. fort quite considerably. For example, an owner found that on his Austin Twelve .Four the pressure which gives the greatest comfort is 301b per sq. in. anything above 331b per sq. in. producing very hard riding unless the road surface is really smooth.

An Appreciable Increase. On several occasions during the summer he checked tyre pressures in the morning before starting on a long run and then checked the pressure agafn (luring the day's running, to find that they had risen to 34 or 351b. Of course, the rise : n temperature can be attributed partly to the rise in air temperature during the day, as between, say, 9 a.m. and 1 p.m., partly to the friction of the tyres on the road, and partly, probably mainly, to internal friction fn the tyre itself owing to the constant flexing to which it is subjected. The interesting point of the problem is to know what to do. If comfort is to be maintained, obviously the tyre pressures should be reduced to normal during the day, at least if one is on, a long run which is likely !o cause the tyre temperature to be but, on the otj|lr hand, when the car is garaged at night and the tyres cool down the pressure will be too low on starting up the next morning. Will the tyres, which are then under-inflated,- heat up and attain their normal pressure with sufficient rapidity to prevent any noticeable elTect on tyre I'fe, which is short ened by undcr.inflation, or would it be wiser to inflate the tyres to tho correct pressure before starting off again, and then once more reduce pressure. when tho tyres become uncomfortably hard? If the car is to be used only for short jouftieys it would probably be wise to inflate to the correct pressure, as otherwise # the tyrc.s might not have a chance of attaining it automatically.

SPARK PLUG CARE AN IMPORTANT POINT The constant whirring of starter motors becomes common as the thermometer gradually drops—not because of inefficiency of the engines, but often due to the neglect of the owners to give sufficient attention to sparking plugs. In operating the average car 10,000 miles, each spark plug fir c s 15 000.000 times and it is not generally understood that plug electrodes gradually burn away and so increase the width of the gap the spark has to jump under high pressure. Although this increase may be only a few thousandths of an inch, it is sufficient to impair -the ignition and starting efficiency. Tlie correct cap imv vary slightly according to the make of car and tvpc of plutf used, but this information is usually given by the instruction manual supplied with the car and should be carefully .cheeked periodically to avoid hard starting ami undue strain on the battery. FIRST DOCTOR'S CAR Inventor of the Barton ni'shin, which was flown in 1905 and probably the first medical m-m to use a motor car On his rounds, Dr F. Alexander 'Barton, died recently in England. While in practice in Bockenhnni. Kent, i n 1897, he acquired from Belgium a 'Hi. p. which he used alternately with his horse-drawn carriage . THE BEACON'S SERVICE TOR SMALT. CLASSIFIED ADVERTISE-"E-'TS lilllMCS BIG RESULTS. 1 .