ADJUSTING THE BRAKES

Southland Times, Issue 23793, 15 April 1939, Page 4

ADJUSTING THE BRAKES

HINTS FOR COUNTRY MOTORISTS IMPORTANT MEASURES FOR CAR SAFETY The proper procedure to be followed in adjusting brakes should not worry tlie average owner in the city. Because the work involved is likely to be rather tedious with the equipment available to the owner, he is well advised to entrust this task to a brake service station. It is not expensive, and such establishments have the quick-acting jacks and gauges which enable them to carry out the work with a minimum of time and labour says The Sydney Morning Herald. The brakes, however, are so vitally important to the safety of a car and its occupants that when an owner finds it inconvenient to visit a service station —such, for example, as those many motorists in back-country regions—some knowledge of the procedure can be extremely valuable. The work is not difficult in itself. The principal trouble lies in the nuisance of jacking up each wheel in turn with the rather inadequate instrument that usually is supplied as standard equipment in a car.

In some ways the simplest brakes to adjust are those operated hydraulically, because the owner is not faced with the task of obtaining perfect equalization of braking force on the back and front pairs. It is only necessary to set each brake in turn so that the drum has just sufficient freedom to turn without friction when the brakes are off. The self-balancing action of the operating liquid within the pipes will do the rest. ADJUSTING POINTS There are two main types of hydraulic brakes: those in which the adjusting points * are outside the drums and those in which they are within. In the first type, the adjusting point consists of a hexagon nut on the brake backing plate. Sometimes there are two of these, each shoe being adjusted separately. Setting these up is simple, as it is only necessary to adjust each shoe in turn so that the drum of the jacked-up wheel will just turn freely, the work being done with an ordinary spanner. I The other type is the application of a well-known mechanical system to hydraulic operation. In this, the two shoes are expanded together by a toothed nut fitting between the two shoes at the top ends. This toothed nut is turned by inserting a screwdriver through an aperture in the brake backing plate and working the nut round in the required direction. There is one variation to this. In a very popular model the aperture, is fitted in the backing plate only on the rear wheels. In the front wheels it is found in the drums, so that in adjusting these it is necessary to remove the front wheels. The latest idea in hydraulic brakes, so far to be found only in certain English models, is the most sensible of aiL A nut on each brake backing plate, engaging with a notch which can be felt, is turned down as far as it will go and then turned back one notch, which automatically sets the brake shoes to just the proper clearance. With this system it is unnecessary even to jack the wheels.

The adjustment of mechanical brakes is rather more difficult to describe, because the methods vary so much. A big number, however, use the shoes which are adjusted by a notched nut already described in connection with .certain hydraulic brakes, and the same procedure is followed. Others are adjusted at the hinged ends of the shoes. So far as shoe adjustment is concerned, it is wise to make a very close study of the car’s instruction book to discover the correct method. But with mechanical brakes adjustment cannot end with the shoes, because it is necessary to equalize the two back brakes and the two front brakes. It is, therefore, essential to jack the wheels in pairs. After the shoes have been adjusted it is necessary Jo. enlist the aid of someone else to sit in the car and partly apply the brakes, so that when each wheel is revolved by hand in turn against the force of the brakes it can be determined whether the force is applied equally to the two wheels. If it is not, further adjustments will have to be made, preferably on the threaded clevis ends of the brake-rods. This may not be possible if the brakes are operated by cables running on conduits, and it may be necessary to slacken one of the shoe adjustments.

The two back wheels should be treated in this manner, and then the front ones, and finally the car should be tested for braking efficiency on the road. If only one wheel shows a skid mark, that one should be slackened, or perhaps the three others will stand a little further tightening. When mechanical brakes are connected to the pedal by a cable running round a pulley, it is important to see that that pulley runs freely, because it is responsible for distributing the braking force equally on to its pair of wheels. In the same way, if a cross bar used for this purpose, and arranged on pivots like the old swingle bar of a two-horse wagon, works stiffly owing to rust in the swivel pins, they must be lubricated well so that the bar works easily. If inefficiency in hydraulic brakes is accompanied by a “spongy” feeling in the pedal, it is fairly obvious that air has made its way into the pipe lines, and the brakes will have to be “bled.” In each brake backing plate, and generally above the adjusting point, will be found a screwed stud. This is removed, and in its place 'is inserted a screwed nipple to which is attached a rubber pipe. This equipment can be obtained from most accessory stores. The pipe is led into a glass jar and the brake pedal pumped so that the liquid from the lines falls into the jar. The air will show its presence by bubbles, and .when they stop appearing that particular brake is finished, the stud can be reinserted and the liquid put back in the master cylinder after the air bubbles have been stirred out of it. , Each brake is treated in a similar manner in turn, and the .master brake cylinder is “topped up” with additional liquid if necessary. There should not be any further trouble.