MOTORING

Hawera Star, Volume XLVII, 19 May 1928, Page 15

MOTORING

WHY TYRES WEAR. THINGS YOG SHOULD KNOW. .f Inflation and Loads. —Proper inflation and loading are so easily neglected that they are still very common tyre aoiises, in spite of the fact that much educational work has been done on this subject. Under-inflation allows the tyre to squash out and gives wider wearing surface to the tyre, thereby creating more road friction. This will cause - last wear. In addition to this, underrinflation may break the internal carcass by the excess strain on the strands and cords. It is also liable to cause a rolling action of the tyre. Two sets of tyres, one run at a recommended inflation and one 61b under-inflated, show a difference in mileage of 25 per cent. Overloading is much the same as under-inflation. It results in the air pressure being higher than necessary to carry the given load. It forces the tyre out, _ increases the contact area If ml the pressure on the road, thus causing more friction and faster wear. Wheel chatter, or a bouncing action of the wheels over a rough stretch of road, comes from overinflation. This causes the tyres to leave the ground, spin, then take hold again, thus grinding off the tread rubber. On over-inflated tyres the car has a tendency to weave on the road; that is, the series of small bounces caused by the tyre being too hard to absorb the small inequalities of the road; thus the car dribbles from one direction to another, causing excessive abrasion, and naturally fast wear. Actual tests have proved that a tyre over-inflated 101 b will give only half the mileage it would have given had it been properly inflated. Temperature. —One of the seasonal factors causing variation in tyre wear is temperature. In cool, wet weather, tyres show very little wear, but in hot, dry weather, the rate of wear is many times greater. With a temperature of 60 degrees, the difference in speed from 20 to 40 miles per hour increases the tyre wear by 84 per cent. With the temperature at 80 degrees a car travelling at 40 miles per hour increases the tyre wear by 133 per cent, ovei the same car travelling at 20 miles per hour, and at 100 degrees the difference in tyre wear travelling at 20 miles per hour and 40 mil%s per hour increases by 226 per cent. This all has reference to atmospheric temperature, but the actual temperature of the road travelled is of major importance; as the temperature increases the abrasive action also increases. Smaller Diameter Wheels. —With the inception of smaller diameter wheels comes more rapid acceleration, quicker braking, and higher speed on curves. In addition to this, a smaller diameter balloon makes more revolutions in a mile than a larger one. In fact, a 28 v 5.25, for example, is 9) per tent, smaller in circumference than a 31 x 5.25, but the actual difference in mileage under the same conditions is 22 per cent. With smaller diameter wheels there is more action per tread unit as it makes and breaks contact with the road, and there is naturally more scuffing and bound to be faster wear to offset the- other advantages. Brake Adjustments.—This is a veryimportant factor, as it has been found upon analysis of a given number of automobiles that 90 per cent, have the brakes very poorly adjusted and the balance is not perfect. The ordinary means of adjusting brakes by jacking up the car and running the wheels, and then stopping them, is not accurate, as the eye alone is the gauge, and may not catch the exactness of the stopping. Again, driving the car over a garage floor, and locking the wheels to see which one slider, first, is not a good test, as the wheels may be locked instantaneously by quick depression of the- foot pedal; while on the road under slighter depression one wheel may take hold more than another. Four wheel brakes must be adjusted perfectly, so that no one tyre will stand more than its normal share of braking. Two wheel brakes must also be properly adjusted, or one tyre will take more strain and wear out faster than the other. In order to adjust brakes properly it,is necessary to use a scientific brake-adjusting machine, and this service is coming into vogue in all principal cities, so there should be no excuse for anyone driving with poorly adjusted brakes. Improper brake adjustment will throw more wear on one wheel or another, as the case mav be.

THE LATE FRANK LOCKHART. A DABING DRIVER. F. Lockhart, who came to an untimely end last week in his attempt to gain the world's motor speed record tor Ii.S.A., was 25 years of age. He was a dirt-track driver in 1924-25, and startled the racing world by winning the Indianapolis “500” in 1926. He has been going great guns since then, and was considered the fastest driver in America; a wizard at getting his car ready, and of a rare mechanical turn of mind which enabled him to get the utmost speed out of any car he drove. In 1926’ and in 1927, he finished second in the American Automobile Association s driving championship. During 1927 lie set a world’s record of 164.28 miles per hour for a 1509 c.e. car,, travelling 171.02 miles per hour one way and 157.55 in the leverse direction on the dry lakes of California. On May 7, at Atlantic City, he qualified his car on the l.j mile -board track there at 147.7 miles per hour, the fastest lap ever made with a car of this engine capacity. In a 100-mile race on a dirt oval track at Cleveland, Ohio, on September 25, 1927, he set new dirt track records from one to 100 miles. His qualification lap with a Hying start was made- at a speed of 92.45 miles per hour, and he finished the 100 miles after easing up, because he was so far in the lead, at S').B miles per hour. The secretary <>l the contest- board (TT.S.A.) tells oi a thrilling experience Lockhart once had, racing on a dirt track at an agricultural show, where the outside fence came close up to the track fence, lhe outside fence was of solid boards, about eight feet high. Lockhart was wearing a leather vest that day, and he caught the sleeve of the vest on the quadrant of his steering wheel. He looked away from the track ahead for an Instant while extricating the worn vest sleeve from its Listening, and when he looked up the turn was right on him. He was going too fast to make it, though, he did make a valiant effort. But it was in vain. He crashed through the low track fence, hit the show ground fence a tremendous blow and shot along it for a couple of hundred feet. The force of hi.s car hitting the fence broke the well rotted posts, and lie rode right down the fence, which had canted to an angle of about four degrees. With his speed l educed he came down off the fence and his car wrecked.