For reasons that should be obvious, your car's braking system is one of the most important systems on the vehicle. For you to be able to drive safely, your vehicle must be equipped with a reliable means of both dissipating the forward momentum created by the engine and drive train and bringing the vehicle from highway speeds to a safe stop in a reasonably short distance. Fortunately, much of the safety engineering that has gone into the design of today's vehicles relates to braking systems. Modern cars and trucks use a hydraulic braking system that holds up well under wear, remains reliable and requires relatively small amounts of maintenance. Routine maintenance must be performed, however, so that your vehicle can continue operating safely. Many drivers choose to have this maintenance performed by professionals at dealerships or brake shops, but there are some aspects that can be performed my do-it-yourselfers who have a reasonable amount of mechanical know-how. Brake work (at least the routine type) requires little in the way of elaborate or specialized tools, and most of the steps are straightforward. As with any serious automotive work, it's critical that you consult your vehicle's service manual to determine any circumstances or requirements that may be unique to your individual car or truck. The most common braking system is one that uses drum brakes (figure A) on the rear of the vehicle and disc brakes (figure B) on the front -- although this is not always the case. Some vehicles have disc brakes all around; others have drum brakes all around. Some vehicles have power brakes, and others do not. Many newer vehicles utilize antilock brake systems (ABS) designed to reduce the possibility of skids in hard-braking situations. ABS systems are regulated by electronic and computer controls, and their benefits have been debated by driving enthusiasts. Regardless of the exact setup, the principles are generally the same for all hydraulic braking systems. The vehicle is equipped with a master cylinder that controls the brake cylinder at each wheel. The hydraulic system uses fluid that creates pressure on specific brake parts, which in turn apply force to moving parts of the wheels. In essence, the braking system utilizes the physical process of friction. Unfortunately, a by-product of friction is wear on the surfaces that come into contact with one another. For that reason it's important to check those surfaces routinely and eventually replace them when they become so worn they lose some of their effectiveness. Whether you intend to undertake brake repair and servicing yourself or you prefer to leave it to the professionals who work on brakes all day long, it's beneficial to understand some of the processes involved and how the parts in the system work in relation to one another. Drum brakes were the first style of brakes used on automobiles, and on early models only the rear-axle wheels were equipped with brakes. On later vehicles drums were added on the front as well. Today's vehicles always have both front and rear brake systems, and if drum brakes are used, they are typically found on the rear axle ( figure C). In drum brakes the brake shoes (figure D) are housed inside the drum. When the driver applies pressure to the brake pedal, the hydraulic system comes into play, and the wheel cylinder causes the brake shoes to move outward so that their outer surface places pressure against the inner surface of the drum (figure E). That pressure is what slows a moving vehicle to a stop or holds a stationary vehicle immobile as long as the brake is applied. Disc brakes are a more recent development. They are most commonly found on the front axle, but some newer vehicles -- especially performance and luxury models -- use disc brakes on all four wheels. Disc-brake systems are preferred in high-performance applications because they are reliable, effective and highly efficient. They bring a vehicle to a stop by applying pressure to both sides of a disc-shaped rotor situated at the ends of the axle. A caliper, housing two brake pads, is situated on top of the rotor (figure F). When the brake is applied, the caliper squeezes the pads against both sides of the rotor to slow and stop the vehicle. Because of their relatively slim design, air can circulate easily around the disc brakes, helping to cool them from friction. The cooling ability is part of what contributes to the overall efficiency of the disc system. Replacement of brake pads is part of regular brake service. Once pads wear out, damage to the rotor can occur. Since brake pads are relatively cheap and rotors are expensive, it's wise to replace the pads regularly.
RESOURCES :
Auto Repair for Dummies
Author: Deanna Sclar
ISBN: 0764550896
Automotive Brakes and Antilock Braking Systems
Model: 0314028382
Author: Kalton C. Lahue
(1995)
To order this title from Amazon.com, click here.
Delmar Learning
Brake Handbook
Model: 0895862328
Author: Fred Puhn
(1985)
Order this book from Amazon.com.
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