TYRE TESTING

Sun (Auckland), Volume II, Issue 372, 5 June 1928, Page 7

TYRE TESTING

MILLIONS OF MILES RUN In the past three years, test car drivers of the Goodyear Tyre and Rubber Company have tested over 19,000,000 tyre miles, according- to figures just compiled by Goodyear engineers. This company has a large fleet of automobiles and trucks for tyre-testing purposes, and they are driven over good and bad roads day and night—under conditions identical with those which the car or truck owner encounters—to learn just how Goodyear tyres stand up. The large fleet of cars and trucks average 600 miles a car for every 2 4 hours. They are driven by men of long experience, whose service with the company averages ten years. Last year the fleet tested 6,605,708 tyre miles, in 1926 the total was 6,777,728 miles, and in 1925 the figure was 5,696,140 tyre miles. Some interesting comparisons can be made between the operations of the testing cars and private cars. The test cars are driven further in one day than the average car is driven in a month, and the daily mileage of one of the Goodyear cars equals that covered by most motorists on a long vacation trip. In the figures of long mileage given by tyres, and the remarkable mileage that the test cars give is told a story not only of the big improvements in tyres, but also in the vast betterment of motor-cars.

against the wind and you will find that the time taken will vary by perhaps 20 per cent. All this difference is due directly to wind resistance. The engine has far more to do with braking than many motorists suppose. For when the throttle is closed the rear road wheels must drive the motor. A good idea of this retarding effect may be had by putting the gear lever into top and trying to push the car along the garage floor. In neutral this can easily be done

with one hand, but it will be quite difficult, if not impossible, when in gear. That is the reason for getting into second or low gear when descending hills.

So in top gear, during ordinary driving, one should get into the habit of leaving the clutch engaged as the brake is applied until the car is almost stationary* It saves the brakes, and effects a much smoother stop. Actually, a skilful driver will, on very treacherous roads, depend solely upon his engine for braking purposes by changing down rapidly as the occasion demands. In this case there is less liability of skidding than if ordinary braking methods were used. The Speed Factor Another point to bo remembered is that the distance in which a car can be stopped varies as to the square of the speed. At 30 miles an hour a good set of brakes will bring a motor to rest in 45 feet, but at 60 miles an hour this distance will not be 90, but 180 feet. Finally, from a practical point of view, there is a wrong and a right way to apply the brakes. When a rear set alone is used, a fierce jab at the brake pedal w'ill mean an immt-diate and violent skid. In emergency it is far better to put the brakes on until just before the wheels lock, and at the same time steer a serpentine course. Care must be taken to make the changes of direction more or less gradual, otherwise the car might overturn. But the object is to cover more ground than would be the case in a straight line, and thus give a better chance of stopping before reaching the impending danger. One of the advantages of front wheel brakes is that even if they do lock—a most unlikely contingencj'—the car will not swerve, but will continue in a straight line.