SAFE MAKES

Evening Star, Issue 22069, 1 July 1935, Page 13

SAFE MAKES

NEED FOR TESTING Car designers have received little enough credit for the excellence of modern brakes, the Pedestrian Association might well have presented them with a grateful testimonial suitably inscribed. Concurrently, a communication of a somewhat different character might be sent to the designers of slippery road surfaces. ... t It is not necessary to travel either very fast or very far in order to appreciate a good braking system. Factors such as the carelessness of many road users, the vast number of signs, and abrupt changes in road surfaces create emergencies which may occur at almost any speed down to a crawl. Consequently no driver, however careful, can afford to neglect tho occasional adjustments which his brakes require. Far too much attention has been concentrated upon the distances in which a car can be stopped, as distinct from the way in which it stops. On a dry road the tyre adhesion available is so great as to cloak tho effects of maladjustment or wear, hut on a greasy surface the way in which brakes operate becomes of paramount importance. When the pedal is depressed the brake shoes should take over their task rapidly yet smoothly; any suggestion of grabbing is apt to lock a wheel or wheels. A tyro which is sliding cannot produce so effective a braking action as ono which is rolling, and, furthermore, loses, directional control. It is for this reason that locking the rear wheels on a slippery surface results in a tail swing which is apt to develop into a skid. Similar considerations show the importance of a proper distribution of the braking forces over the four wheels. In course of time wear and tear may result in one of the brakedrums taking much more than its fair share of the work, with the result that the wheel concerned will very readily become locked in the course of emergency braking on grease. Most big garages are equipped with special brake-testing apparatus, by means of which proper adjustments can rapidly be carried out. Given good brakes, the results actually obtainable will depend to a marked extent upon the efficiency of the driver; He must school himself to uso the pedal with discretion on a slippery road, even if an emergency calls for as quick a stop as possible. Suddenly to apply a heavy pressure on the pedal will probably result in the car sliding through a much greater distance than that in which it could have been stopped by more gentle treatment. Secondly, the driver must always be alert in order to reduce, so far as is humanly possible tho reaction time which elapses between noting an emergency and applying the brakes. Lengthy experience and theoretical considerations go to show that only very rarely is' it possible to stop a car in less than 30ft from 30 m.p.h. Brakes capable of giving this result show an efficiency of 100 per cent. 'Modern brakes are very good, but they cannot perform miracles. Properly adjusted and used they do, however, provide the best possible safeguard against accidents.