BRAKE COMPONENT BRAKING SYSTEMS

Beyond brake pads and pedals, brake systems have a lot of brake components that help your car perform better and drive safer. The brake master cylinder is the first, and perhaps most important, component in your braking system because it sets the rest of the system in motion. The master cylinder is activated by pressing down on the brake pedal, which pushes a piston through the cylinder to force brake fluid through the brake lines. Most modern cars have brakes on all four wheels, operated by a hydraulic system . The brakes may be disc type or drum type. The front brakes play a greater part in stopping the car than the rear ones, because braking throws the car weight forward on to the front wheels.

start Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 OBJECTIVES: After studying Chapter 67, the reader should be able to: • • • • • Prepare for ASE Brakes (A5) certification test List the parts and terms for disc and drum brakes Describe brake design requirements List the six brake system categories Discuss federal braking and stopping standards Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 KEY TERMS: adjustable pedals • antilock braking system (ABS) • apply system base brakes • boost system • brake balance control system • brake pedal • brake warning lights Department of Transportation (DOT) • disc brakes • drum brakes electric adjustable pedals (EAP) Federal Motor Vehicle Safety Standards (FMVSS) • foundation brakes Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 KEY TERMS: gross vehicle weight rating (GVWR) hydraulic system lightly loaded vehicle weight (LLVW) parking brake red brake warning lamp service brakes • snub • wheel brakes Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 Brakes are by far the most important mechanism on any vehicle because the safety and lives of those riding in the vehicle depend on proper operation of the braking system It has been estimated that the brakes on the average vehicle are applied 50,000 times a year! Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 HOW BRAKES STOP VEHICLES Brakes are an energy-absorbing mechanism that converts vehicle movement into heat while stopping the rotation of the wheels All braking systems are designed to reduce the speed and stop a moving vehicle and to keep it from moving if the vehicle is stationary Service brakes are the main driver-operated brakes of the vehicle, and are also called base brakes or foundation brakes See Figure 67–1 Continued Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 Figure 67–1 Typical vehicle brake system showing all typical components Continued Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 Most vehicles built since the late 1920s use a brake on each wheel To stop a wheel, the driver exerts a force on a brake pedal Force on the brake pedal pressurizes brake fluid in a master cylinder This hydraulic force (liquid under pressure) is transferred through steel lines and flexible brake lines to a wheel cylinder or caliper at each wheel Hydraulic pressure to each wheel cylinder or caliper is used to force friction materials against the brake drum or rotor The heavier the vehicle and the higher the speed, the more heat the brakes have to be able to absorb Long, steep hills can cause the brakes to overheat, reducing the friction necessary to slow and stop a vehicle See Figures 67–2 and 67–3 Continued Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 Figure 67–3 When driving down long,steep grades, select a lower transmission gear to allow the engine compression to help maintain vehicle speed Figure 67–2 Brakes change the energy of the moving vehicle into heat Too much heat and brakes fail, as indicated on this sign coming down from Pike’s Peak in Colorado at 14,000 ft (4,300 m) Continued Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 DRUM BRAKES Drum brakes are used on the rear of many rear-wheel-drive, front-wheel-drive, and four-wheel-drive vehicles When drum brakes are applied, brake shoes are moved outward against a rotating brake drum The wheel studs for the wheels are attached to the drum When the drum slows and stops, the wheels also slow and stop Drum brakes are economical to manufacture, service, and repair Parts are readily available and reasonably priced On some vehicles, an additional drum brake is used as a parking brake on vehicles equipped with rear disc brakes See Figures 67–4 and 67–5 Continued Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458