The single-piston wheel cylinder (fig. 7-7) is used when it is desired that both brake shoes be independently self-energizing, especially on the front wheels. With this design it is necessary to have two wheel cylinders, one for each shoe. Each cylinder has a single piston and is mounted on the opposite side of the brake backing plate from the other cylinder. Such an arrangement is shown in figure 7-8.

NOTE
For further information on wheel cylinders, refer to "Drum Brake Assemblies" in this chapter.

Brake Lines and Hoses
Brake lines and hoses transmit fluid under pressure from the master cylinder to the wheel cylinders. The brake lines are made of double-wall steel tubing with double-lap flares on their ends. Rubber brake hoses are

Figure 7-7.- Wheel cylinder configurations.

Figure 7-8.- Double-anchor, double-wheel cylinder configuration.

used where a flexing action is required. For example, a brake hose is used between the frame and the front-wheel cylinders or disc brake calipers. This design allows the wheels to move up and down, as well as side to side without damaging the brake line. Figure 7-9 shows the details of how brake lines and brake hoses fit together.

A junction block is used where a single brake line must feed two wheel cylindersorcalipers. It is a simply a hollow fittingwith one inlet and two or more outlets.

Mounting brackets and clips are used to secure brake lines and hoses to the unibody or frame of the vehicle. The mounting brackets help hold the assemblies secure and reduce the vibration which causes metal fatigue, thereby preventing line breakage.

Figure 7-9.- Brake lines and hoses.

Steel lines seldom need replacing except in areas where they rust from exposure to salt air or constant high humidity. Flexible hoses should be inspected at regular maintenance periods for any signs of cracking or abrasion. Should the outer protective covering be cracked or badly abraded, it should be replaced.