ALTRACO ELECTRONIC DISC BRAKE CALIPER Manual de Serviço descarregar pdf (Página 5)

Ball-and-Ramp Caliper Service

The ball-and-ramp caliper assembly works by using

three steel balls along matching tapered ramps to apply the

brake pads. To replace the pads without disassembling the

caliper, a special tool, Figure 13-21, must be used to turn

the piston into the caliper bore. Carefully push the piston

back into the caliper using the special tool to bottom the

piston in the caliper bore. There is no way to bottom the

piston without using this tool.

Cam-Type Caliper Service

The cam-type caliper is a simple design in which an

eccentric cam moves a rod. The rod pushes the piston

and pads into contact with the rotor. The rod is threaded

and mates with an adjusting nut in the piston. The rod and

adjusting nut remove any slack caused by pad wear. To

retract the piston when new pads are installed, the piston

should be turned clockwise as shown in Figure 13-22.

Rear Caliper Reinstallation

Rear caliper reinstallation is the reverse of installation.

If it was removed, reinstall the rotor. Place the new pads in

the caliper or on the rotor assembly. Reinstall the caliper and

reconnect the parking brake linkage if it was removed. If the

vehicle uses an electrical wear sensor, attach the electrical

connector. If needed, bleed the system. If the vehicle has a

drum-in-disc system, be sure to adjust the parking brake. Be

sure to stake the pads if necessary.

Adjusting Rear Disc Brake Calipers

After rear disc brake service, you may need to adjust

the caliper pistons to the rotors. In some cases, the brake

pedal only needs to be pumped several times to bring the

pads in adjustment. However, a special adjustment proce-

dure is sometimes needed to bring the pads into position

and to obtain a good pedal.

Using a flat-head screwdriver, carefully position the

tip against the top lip of the caliper piston, Figure 13-23.

Clamp a pair of vice grips on the caliper’s parking brake

actuating mechanism.

Chapter 13 Disc Brake Service 217

Figure 13-17.

A—A rear wheel disc brake assembly, with the

parking brake cable and hook disconnected from the caliper

apply lever. B—A screw-type rear disc caliper assembly.

Remove the parking brake cable and lever to push in the piston.

(Chevrolet)

Pad

Caliper

mounting

bolt

Apply

lever

Parking

brake

assembly

Pad sensor

electrical

connector

Sensor

wire

Splash

shield

Rotor

Figure 13-18.

A spanner wrench is sometimes needed to turn

screw-type rear caliper pistons into the body. (Bendix)

Caliper

housing

Piston

Bench

vise

Spanner

wrench

"D" shaped

locator

While carefully prying against the piston, use the vice

grips to apply and release the parking brake. The caliper

piston should adjust the pads until they just rest against the

rotor. If the caliper piston fails to move, try tapping the

caliper piston area with a ball peen hammer. Be careful not

to damage the bleed screw. If the piston continues to stick,

remove the caliper and perform an overhaul.

Rotor Service

The following sections discuss the service of disc

brake rotors. The condition of the rotor is as important as

pad condition. Many common disc brake problems, such

as noises and pulsation, are caused by the rotor. Therefore,

it is very important that you carefully check the rotors

when the pads are replaced.

Sometimes the rotor is not refinished when the pads

are replaced. However, the usual procedure in most shops

is to refinish the rotor to allow it to wear into the new disc

pads. Whether it is refinished or not, the rotor should be

checked as explained in the following paragraphs.

218 Auto Brakes

Note: In some cases, this is easier to

perform using a box-end wrench.

Figure 13-20.

This particular brake caliper setup requires the

tab on the brake shoe to be placed in one of four caliper piston

cutouts (slots). (Nissan)

CutoutCaliper

piston

Shoe

Ta b

Pad

Caliper

Rotate

Figure 13-19.

A—Parking brake lever removal can allow a screw caliper’s piston to be pressed in. B—Pressing the caliper piston in

with two pairs of adjustable pliers. (General Motors)

Nut

Return

spring

Lever

seal

Antifriction

washer

Parking

brake cable

Bolt

Shoe tab

Caliper

housing

Shoe tab

Caution: Some manufacturers recommend

that rotors be refinished only if they are

scored or out-of-round, which would pro-

duce a pulsation. In some cases, extensive driving is

required after refinishing to burnish the pads prop-

erly. Some rotors cannot be machined and must be

replaced if they are scored or out-of-round.

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