Chap67

[object Object],[object Object],[object Object],[object Object],[object Object],OBJECTIVES: After studying Chapter 67, the reader should be able to:

HOW BRAKES STOP VEHICLES ,[object Object],[object Object],Continued

Figure 67–1 Typical vehicle brake system showing all typical components. Continued

[object Object],[object Object],Continued

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). Figure 67–3 When driving down long,steep grades, select a lower transmission gear to allow the engine compression to help maintain vehicle speed. Continued

DRUM BRAKES ,[object Object],Continued

Figure 67–4 Typical drum brake assembly. Continued

Figure 67–5 Drum brake assembly as used on the right rear wheel.

DISC BRAKES ,[object Object],Continued Figure 67–6 Typical disc brake assembly. A disc brake operates by squeezing brake pads on both sides of a rotor or disc that is attached to the wheel. Due to the friction between the road surface and the tires, the vehicle stops.

BRAKE DESIGN REQUIREMENTS ,[object Object],Continued ,[object Object],[object Object],[object Object],[object Object],[object Object]

[object Object],Continued ,[object Object],[object Object]

[object Object],[object Object],[object Object],Continued

[object Object],NOTE: It is this movement of the friction material that causes brake noise (squeal). Various movement dampers are used by the vehicle manufacturers to help control any movement that does occur. It is important that every technician restore the operation of all aspects of the braking system whenever they are serviced, even the noise dampers.

BRAKE SYSTEM CATEGORIES ,[object Object],Continued Figure 67–7 Typical brake system components.

Figure 67–9 The red brake warning lamp alerts the driver to a possible brake system fault. Figure 67–10 The ABS dash warning lamp alerts the driver to a possible antilock brake system fault. Continued

[object Object],How Do Adjustable Pedals Work? Pedal and seat system position is usually included as part of memory seat function and can be set for two or more drivers. 1 . Adjustable pedal position switch — allows the driver to position the pedals. 2 . Adjustable pedal assembly — motor, threaded adjustment rods and a pedal position sensor. Figure 67–8 A typical adjustable pedal assembly. Both the accelerator and the brake pedal can be moved forward and rearward by using the adjustable pedal position switch.

ANTILOCK BRAKE SYSTEM OPERATION ,[object Object],Continued It is the friction between the tire tread and the road that does the actual stopping of the vehicle. ABS does not mean a vehicle can stop quickly on all road surfaces. ABS uses sensors at the wheels to measure the wheel speed. If a wheel is rotating slower than the others, indicating possible lockup (for example, on an icy spot), the ABS computer will control the brake fluid pressure to that wheel for a fraction of a second. A locked wheel has less traction to the road surface than a rotating wheel .

Figure 67–11 Typical components of an antilock braking system (ABS) used on a rear-wheel drive vehicle. Continued

FEDERAL BRAKE STANDARDS ,[object Object],Continued

[object Object],Continued ,[object Object],[object Object],[object Object],[object Object],The majority of FMVSS 135 consists of a comprehensive test procedure designed to reveal any weakness in a vehicle’s braking system. The test is used by manufacturers to certify the braking performance of all new vehicles available for public purchase.

[object Object],Do the FMVSS 135 Standards Apply to Replacement Brake Part Performance? Although these tests may seem extreme, remember that they are only a minimum standard of performance. Any brake repair work should also leave the brake system capable of meeting FMVSS 135.

BRAKE REPAIR AND THE LAW ,[object Object],Regardless of specific laws governing brake repair, a tech is always liable for damage or injuries resulting from repairs performed in an unprofessional or unworkmanlike manner. There is only one acceptable goal when making brake system repairs: to restore the system and its component parts so they perform to original specifications. The purpose of any repair is to restore like-new performance .

SUMMARY ,[object Object],[object Object],[object Object],Continued

SUMMARY ,[object Object],( cont. )

Chap67

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Chap67