BRAKING TESTS

Waipa Post, Volume 42, Issue 3303, 30 May 1931, Page 7

BRAKING TESTS

The importance of correct adjustment of four-wheel automobile brakes was recently demonstrated by tests conducted at the National Physical Laboratory, London. A working model of a car was used in the experiments. It was found that the model skidded perfectly straight for four feet with all four brakes on and the wheels locked. With the two rear wheels locked the car skidded nine feet forward, and deviated on one foot to one side, while with the two front wheels locked the machine skidded five feet forward and kept a straight course. With both front and the right-hand rear wheel locked there was a skid of four feet and ahalf, and a slight deviation to one side. The investigation resulted in the following conclusions: —The tendency to overturn is specially marked at high speeds with the following brake combinations. Two rear brakes only in operation a diagonal pair of brakes— and also when one front and the two rear brakes are applied. In the case where the front brakes lock the wheels of a car, the driver has little or no control over the direction of travel so long as those wheels are locked. On the other hand, when the rear wheels lock, the stability of the motion is better under control. These experiments indicate the importance of correct brake adjustment.

Nowadays, with high speeds and more road traffic, the efficiency of automobile brakes becomes more important than ever. The standardising of four-wheel brakes has given to motorists greater control over their vehicles, but at the same time has introduced a more intricate braking system when it calls for adjustment. The appearance of so many black smears of rubber on the surface of city streets is only too significant evidence of the number of automobiles that are running with unevenly adjusted brakes. Admittedly not all brake systems are easy to adjust correctly, and where there is any doubt in this respect it is advisable to let an experienced mechanic handle the job.

For those who desire to handle the adjustment themselves, the Dunlop Company suggests that the best way is to jack up both axles so that all wheeTs are free of the ground at the same time, then cut a strut to press down the brake pedal from the dash or from front of seat, whichever is the most convenient. • Go to each wheel in turn and make the adjustment so that you can just manage to turn the wheel by using the whole of your strength.

In carrying out such an adjustment it is well to remember that worn threads of tyres do not give the same road grip, as do covers with the patterned tread in good condition; also that tyres should be evenly balanced as regards tread surface on the wheels of each axle.