Braking System 103

BRAKING SYSTEM – I

STRUCTURE

Objectives

Description of Braking System

Precautions

Removal of Master Cylinder from the Car

Dismantling Tandem Master Cylinder

Inspection of Master Cylinder Components

Assembly of Master Cylinder

Installing the Master Cylinder in the Car

Tracing the Brake Line

Bleeding of Brakes

Installing the Air Cleaner

...........................................................................................................................

Summing Up

Possible Answers to Self-check Questions

Terminal Questions

References

Glossary

35

BRAKING SYSTEM – I

The Maruti car uses hydraulic braking system with a tandem master cylinder

for enhanced safety. The front brakes are of the hydraulic disc type while the rear brakes are hydraulic drum brakes of the leading and trailing shoe type. The parking brake system is mechanical.

In this lesson we will learn to overhaul the tandem master cylinder, trace the

brake lines, and bleed the system. In the next lesson of this unit, we will learn how to overhaul the front and rear brakes.

Objectives

After going through this lesson, you will be able to:

i. Understand the braking system of Maruti 800 car ii. Remove, overhaul, and re-install the master cylinder iii. Trace the brake lines iv. Bleed the braking system

Description of Braking System

The Maruti car uses hydraulic braking system with a tandem master cylinder

from which four brake pipes constitute two independent circuits, each of which applies brakes on two road wheels. This enhances safety, for the reason that even if one circuit fails due to leakage of the brake fluid, the other circuit still functions (refer section 4.5 of course 101) and it is possible to stop the vehicle, even though the braking is not as efficient as with four wheel brakes. Further, the Maruti car uses the diagonal split system where the front left (FL) and the rear right (RR) brakes are applied by the primary circuit and the front right (FR) and the rear left (RL) brakes are applied by the secondary circuit. This prevents the car from turning around when the brakes are applied only on two wheels, when one circuit has failed.

The front brakes are of the hydraulic disc type while the rear brakes are hydraulic drum brakes of the leading and trailing shoe type. The front and the rear brakes have dissimilar components and operate differently.

The parking brake system is mechanical. It applies a braking force only to the rear wheels by means of a cable and mechanical linkage. The brake shoes used for the parking brake are the same as the ones used for the foot brakes.

36

Self-check Questions

1. How does the tandem master cylinder enhance safety? 2. What is the advantage of the diagonal split system? 3. ________ and _________ brakes are applied by the primary circuit 4. Front brakes are ____________ and rear brakes _______________ type 5. Parking brakes are ___________________ type

Removal of Master Cylinder from the Car

Hereunder we give the steps to be followed for removing the tandem master

cylinder from the car.

Unlock, lift up and hook the bonnet in the open position.

Unscrew the nut on the air cleaner cap.

Loosen the bolt on the bracket of the air cleaner.

Remove the hose.

Remove the air cleaner.

Twist the cap open on the brake fluid reservoir.

Suck the brake fluid out with a syringe.

Remove the two screws holding the reservoir to the tandem master cylinder.

Lift off the reservoir.

Disconnect the coupler of the brake switch.

Set aside the cap of the reservoir. The float in the cap senses the level of the brake fluid in the reservoir and

lights up the brake warning light when the level goes low.

Unscrew the four flare nuts at the brake master cylinder with a No 10 open end spanner.

Disconnect the pipes.

Remove the split pin.

Remove the rod pin which connects the master cylinder push rod fork and the brake pedal arm.

Unscrew the two attaching nuts that hold the master cylinder to the engine fire wall.

Take the master cylinder out.

Fig. 3.1: Tandem master cylinder.

37

Dismantling Tandem Master Cylinder

Remove the two grommets with a screw driver.

Remove the circlip from the groove in the barrel of the master cylinder with the help of a circlip remover.

Remove the push rod along with the dust cover.

Remove the primary piston by blowing compressed air into the intake port, shown in the figure, of the secondary chamber, taking care to blow the air cautiously as the piston may jump out.

Unscrew the piston stopper bolt.

Remove the secondary piston by blowing compressed air into the hole from which the piston stopper bolt was removed.

The secondary piston assembly is

dismantled first.

Remove the spring seat from the return spring.

Remove the piston cup and the metal washer from the piston.

Remove the piston pressure cap from the piston.

The primary piston assembly is

dismantled next.

Unscrew the bolt holding the return spring to the piston.

Remove the screw, screw guide, spring, and spring seat from the piston.

Remove the piston cup, metal washer and then the pressure cap at the other end of the piston.

During assembly, the two piston assemblies, shown in the figure, should be

assembled in the barrel in the prescribed sequence.

Fig. 3.2: (a) Intake or inlet port. (b) Primary piston assembly.

Fig. 3.3: The two piston assemblies.

38


6. What arrangement is made for indicating low level of brake fluid in the reservoir? 7. How is the primary piston removed? 8. How is the secondary piston removed?

Inspection of Master Cylinder Components

Ensure that the float is not damaged and is free to rise and fall.

Inspect the locks in the cap to ensure that they are not broken.

Check that the coupler is in a good condition.

Inspect the reservoir for cracks or damage.

The rubber grommets should be changed during assembly.

Inspect the bore of the barrel to check that it is smooth and shiny and does not have scratch marks.

The figure shows the intake and

the fluid return holes which connect the reservoir to the two chambers of the barrel.

Check that the threads where the brake pipes and the secondary piston stopper bolt are screwed in are not damaged.

Check that the spring is not broken or weakened.

Check that the piston is not worn.

The screw, screw guide, spring, and the piston of the primary piston assembly should similarly be inspected for wear or damage.

Inspect the push rod ball. It should not be worn or rusted.

Check the circlip. It should be in good condition.

Assembly of Master Cylinder

The genuine TVS Girling brake parts should always be used during overhaul.

The kit contains all the parts that should be replaced during the overhaul of the master cylinder.

Fix the spring seat to the secondary piston return spring.

Fix the piston pressure cap.

Install the metal washer and the piston cup on the piston.

Fig. 3.4: Intake and fluid return holes.

39

Fix the spring seat onto the spring on one side and insert the screw guide and the screw from the other side to begin the assembly of the primary piston.

Place the metal washer and the piston cup on the primary piston.

Place the spring along with the spring seat on to the piston cup.

Tighten the screw with a Philips head screw driver.

Install the pressure cap in the groove provided on the piston for this purpose.

Brake oil should be applied during fitment as it makes the task easy. The parts in the barrel are assembled next.

Apply brake oil to the rubber parts before assembly.

Insert the secondary piston return spring with the seat fixed to it.

Push the piston in the barrel.

Fix the O-ring onto the bolt.

Push the secondary piston as far inside the barrel as possible.

Screw in the stopper bolt in its hole.

Tighten the bolt with a Philips head screw driver.

The stopper bolt limits the travel of the secondary piston.

Install the primary piston with its spring side going in first.

Insert the push rod along with washer and fix the circlip with a circlip plier in the groove in the master cylinder body.

Check for free movement of the piston assemblies in the barrel.

Mount the dust cover onto the master cylinder body.

Insert the grommets in the two holes in the body.

Fix the reservoir, with its tubes going through the grommets, to the master cylinder body with the help of the two screws.

Pour brake oil in the reservoir.

Pump the push rod and ensure that fluid pressure develops in the barrel.

The development of fluid pressure in the barrel results in the brake fluid being squirted out of the four holes where the brake pipes are fitted.

Installing the Master Cylinder in the Car

Insert the push rod of the master cylinder through the engine firewall and fix the flare nuts of all the four brake pipes.

Tighten the flare nuts with an open end spanner.

Fig. 3.5: Inserting the grommets.

40

Place a washer each over the two mounting screws and screw in the nuts.

Tighten the nuts with a ring spanner.

Fix the brake warning light coupler.

The remaining steps in this procedure are performed from inside the passenger compartment.

Fix the rod pin to hold the fork of the push rod and the brake pedal lever.

Insert the split pin in the rod pin and bend it properly.

The two steps above connect the brake pedal to the master cylinder push rod.


9. Which make of brake parts should be used? 10. What is done to make assembly of parts in master cylinder easy? 11. Which piston is inserted first? 12. Which side of the primary piston is inserted first? 13. How is the secondary piston held in the master cylinder?

Tracing the Brake Line

When a loss of the brake fluid is reported, the joints in the pipe and the brake

pipes should be checked for leakage or breakage.

There are four lines that come out of the master cylinder, with one line for each wheel brake. The line at the front, that is, from the secondary chamber, and coming from the underside of the master cylinder, travels downwards along the body of the car and goes to the front right wheel. The one at the front and coming from the side of the master cylinder travels along the engine firewall and enters the passenger compartment, traveling along the floor and coming out at the rear towards the rear left wheel. The flexible pipe travels down and is held in the bracket of the axle where again a steel pipe is attached to it. The steel pipe travels over the axle, is clamped to it, and then ends in a flare nut which is screwed in the wheel cylinder. The flexible pipe is installed at strategic locations, so that the up and down movement of the car does not stress the steel pipe unnecessarily, causing it to break.

Similarly, the lower pipe from the primary chamber goes to the front left wheel and enters the cylinder of the caliper. The pipe coming out from the side of the master cylinder goes to the rear right wheel along the same path as the one adjacent to it and is connected to the wheel cylinder. Thus, the hydraulic lines of the braking system used in the Maruti 800 car are based on the diagonal split system, which improves safety during braking.

41

Bleeding of Brakes

The bleeding operation is performed to remove air from the hydraulic brake

system. The removal of air is necessary because air is compressible and if it is present in the system, braking force is not be transmitted fully. Hence, bleeding is performed whenever the system is overhauled, any component is changed or when a brake pipe or hose is disconnected. Bleeding is first done at the wheel which is farthest away from the master cylinder and then at the caliper of the same brake line, that is, the rear right wheel cylinder and then the front left brake caliper or the rear left wheel cylinder and then the front right brake caliper.

Fill the master cylinder with brake fluid.

Care should be taken that during the bleeding operation, the master cylinder is at least half full.

Sit on the driver’s seat and press the brake pedal several times till the development of the fluid pressure in the cylinder is felt.

Help should be sought from another person to sit at the road wheel from

which bleeding is to be done and to attach a vinyl tube to the bleeding nipple, inserting the other end of the tube in a bottle. If a ring spanner is being used, it should be installed over the nut before attaching the tube. Otherwise, an open end spanner may also be used.

Loosen the bleeding nipple one-third to half a turn, keeping the pedal depressed.

When this operation is performed, brake fluid comes out through the tube with

air bubbles in between. When the fluid pressure in the cylinder is almost depleted, the nipple is retightened and the whole operation is repeated over again until there are no more air bubbles in the fluid that comes out of the tube. Once the air bubbles have stopped, the bleeding nipple is tightened while keeping the brake pedal depressed. Air would have been removed from this part of the system after the operation.

The bleeding operation is then performed on the front wheel, and if done properly, the brake pedal does not feel spongy. The level of brake fluid in the reservoir comes down during bleeding. Hence, it should be filled with more fluid.

Bleeding is done on the other brake line similarly.

Top up the brake fluid to the MAX level mark in the reservoir.

Close the cap.

42


14. Which brake lines go to the FR, RR, FL, and RL wheels? 15. Why is bleeding done? 16. In which wheel is bleeding done first?

Installing the Air Cleaner

Place the air cleaner over the air horn of the carburetor.

Fix the air cleaner bracket in the bolt of the cylinder head cover.

Fix the ventilation hose in the air cleaner.

Place a washer and screw-in the nut over the air cleaner cap and tighten it.

Tighten the bolt of the cylinder head cover.

Close the bonnet.

Test drive the car.

Summing Up

In this lesson, we studied the hydraulic braking system of the Maruti 800 car

and learnt to overhaul the tandem master cylinder. We traced the brake line and understood the importance and procedure of bleeding. It is instructive to see how two independent circuits are formed from the two chambers of the tandem master cylinder and how the reservoir also has two interconnecting compartments to feed the two chambers of the tandem master cylinder.

In the next lesson, we will learn how to dismantle, inspect and assemble the components of the front and rear braking system.


1. by having 2 independent circuits each applying brakes to 2 wheels 2. the car does not rotate when braked 3. FL & RR 4. disc, drum 5. mechanical 6. master cylinder cap has float which switches ON the warning light when level

is low 7. by blowing compressed air in the intake port of secondary chamber 8. by blowing compressed air in the hole of piston stopper bolt 9. TVS Girling 10. apply brake oil during assembly 11. secondary piston 12. spring side of primary piston 13. by stopper bolt 14. The line at the front, that is, from the secondary chamber, and coming from

the underside of the master cylinder, travels downwards along the body of the

43

car and goes to the front right wheel. The one at the front and coming from the side of the master cylinder travels along the engine firewall and enters the passenger compartment, traveling along the floor and coming out at the rear towards the rear left wheel. The lower pipe from the primary chamber goes to the front left wheel and enters the cylinder of the caliper. The pipe coming out from the side of the master cylinder goes to the rear right wheel cylinder.

15. to remove air from the system so that brakes are not spongy 16. Bleeding is first done at the wheel which is farthest away from the master

cylinder and then at the caliper of the same brake line, that is, the rear right wheel cylinder; then the front left brake caliper or the rear left wheel cylinder and then the front right brake caliper.

Terminal Questions

1. Describe the braking system of the Maruti 800 car. 2. Explain how the diagonal split system with tandem cylinder enhances safety.

References

1. Maruti 800 Service Manual

Glossary

Bleeding Removing air from the braking system.

Disc brakes Braking effort is applied on a disc connected to the road wheel by friction pads which are operated by hydraulic pressure.

Drum brakes Braking effort is applied on a drum connected to the road wheel, by friction linings fixed to brake shoes which are operated by hydraulic pressure.

Grommet An eyelet usually made from rubber used to protect, strengthen, or insulate around a hole or passage.

Leading shoe Shoe that comes first after the wheel cylinder in the direction of rotation. It applies greater braking effort than the trailing shoe.

Parking brake Brakes applied when the car is stationary so that it does not move when on a slope.

Tandem master cylinder Master cylinder with two pistons arranged one ahead of the other; one piston operates 2 wheel brakes and the other the other 2 wheel brakes.

44

Trailing shoe Shoe that comes second after the wheel cylinder in the direction of rotation. It applies lesser braking effort than the leading shoe.

TVS Girling Company manufacturing brake parts.

BRAKING SYSTEM – II

STRUCTURE

Objectives

Special Tools Required

Precautions

Overhaul of Front Disc Brakes

4.3.1 Removal of Front Brake Caliper

4.3.2 Dismantling Caliper Assembly

4.3.3 Inspection of Caliper Components

4.3.4 Assembly of Caliper

4.3.5 Mounting the Front Wheel

Overhaul of Rear Drum brakes

4.4.1 Removal of Rear Brake Drum and Back Plate

4.4.2 Dismantling Back Plate and Wheel Cylinder

4.4.3 Inspection of Parts

4.4.4 Assembly of Wheel Cylinder

4.4.5 Assembly of Back Plate

4.4.6 Mounting the Rear Wheel

Activity

Summing Up


Terminal Questions

References

Glossary

BRAKING SYSTEM – II

In the last lesson we studied how to overhaul the tandem master cylinder, trace

the brake lines, and bleed the system. In this lesson we will learn how to overhaul the front and rear brakes. The front brakes are of the hydraulic disc type while the rear brakes are hydraulic drum brakes.

Objectives

After going through this lesson, you will be able to:

i. Overhaul the front disc brakes ii. Overhaul the rear drum brakes

Special Tools Required

1. Brake drum remover 2. Sliding hammer

Precautions

1. Sliding hammer should be used with care. If your finger happens to come

between the handle and the weight (slide) it will give a very painful blow.

Overhaul of Front Disc Brakes

For description of hydraulic disc brakes refer section 4.2.2 of CAF 101.

Removal of Front Brake Caliper

Loosen the wheel nuts.

Lift the front wheel up with a hydraulic garage jack.

Unscrew the wheel nuts completely.

Remove the wheel.

Fig. 4.1: Caliper assembly.

The caliper and the disc of the front wheel brake will clearly be visible now.

Unscrew the banjo bolt.

Remove the brake pipe.

Remove the two bolts holding the caliper to the steering knuckle.

Push the brake pads away from each other with a screw driver.

Pull the caliper out.

Place a safety stand under the car.

Remove the hydraulic jack.

Dismantling Caliper Assembly

Unscrew the banjo bolt which connects the flexible brake pipe to the cylinder.

Unscrew the bleeding nipple from the caliper.

Remove the two mounting bolts.

Unscrew the two caliper pin bolts which hold the caliper to the carrier and remove the carrier, the brake pads, and the tensioner strips.

Remove the caliper pins from the carrier.

Remove the boot.

Remove the piston from the cylinder.

In order to remove the piston, compressed air is blown into the cylinder through the hole from which the banjo bolt was removed. This pressurized air pushes the piston out. A clean cloth should first be placed in front of the piston before blowing the air, so that the piston does not get damaged when it comes out.

Remove the piston seal with a blade of the feeler gauge.

The parts of the caliper assembly which have been removed include the caliper carrier, mounting bolts, caliper pins, brake pads, tensioner strips, boot, piston, piston seal, caliper, bleeding nipple, banjo bolt, and the caliper pin bolts.

Inspection of Caliper Components

Check that the inside bore of the cylinder is smooth.

Inspect that the piston surface is smooth and shiny and does not have scratch marks.

Fig. 4.2: Caliper carrier.

The piston seal and boot should be changed during assembly.

Inspect the brake pad lining for wear.

The standard thickness of the brake pad lining is 15.5 mm and the wear limit may be specified as 6.5 mm or 8.5 mm depending on design. The wear limit is, therefore, needed to be checked from the manual. Alternatively, the groove which is provided on each pad lining may be checked. If the groove has disappeared, the pad should be replaced. The pad lining should never be polished with sandpaper because abrasive particles may get deposited in the lining and these may damage the disc. If the lining is worn or scratched, it should be replaced with a new one.

Check that the tensioner strips are not bent or broken and replace them if they are damaged.

Inspect that the caliper pin is not worn.

Check the thickness of the disc with a micrometer. The standard thickness of the disc is 10 mm and the wear limit is 8.5 mm.

Inspect the brake disc for deep scratches. If there are scratches only on one side, the disc may be polished.

Fig. 4.3: Components of the caliper assembly.

The disc is checked for deflection next. Before checking for deflection, it should

first be ensured that the front wheel bearing is not loose. In order to check the deflection, the variation in reading on the dial of the dial gauge is noted while rotating the disc. The limit on deflection is 0.15 mm.

Assembly of Caliper

Apply brake oil to the piston seal and in the groove.

Install a new piston seal in the groove in cylinder, keeping the wider end of the seal towards the outside and taking care not to twist the seal.

The piston seal is used to provide a liquid-tight seal between the piston and the

cylinder and it also helps to adjust the clearance between the pad and the disc automatically when they get worn.

Fit the rubber boot onto the piston

Apply brake oil to the surface of the piston and fit it in the cylinder.

Position the outer end of the piston so that it projects out of the end of the cylinder by about 10 mm to facilitate installation of the boot.

The caliper is installed to the carrier next.

Apply grease to the two caliper pins and ensure that the pins move easily in the carrier holes.

Place the carrier in front of the caliper.

Screw in the caliper pin bolts lightly.

Fix the two tensioner strips by pressing them in place with a screw driver.

Fit the two brake pads one by one over the strips.

Tighten the caliper pin bolts fully.

Screw in the bleeding nipple and the banjo bolt lightly in the holes in the caliper.

The two mounting bolts are used to fix the caliper to the steering knuckle.

Mounting the Front Wheel

Install the brake caliper over the disc and screw in the mounting bolts in the steering knuckle.

Tighten the bolts.

Fix the flexible brake pipe with banjo bolt to the brake cylinder.

Mount the front wheel and screw in the wheel nuts.

Tighten the wheel nuts with a wheel spanner.

Lift the wheel with the hydraulic garage jack and remove the safety stand.

Lower the jack and remove it from under the car.

Fix the spindle cap.

Self-check Questions 1. What is caliper? 2. What is a banjo bolt? 3. How is piston removed from the cylinder? 4. What precaution would you take when removing the piston? 5. What is the standard thickness of the brake pad and what is the service limit? 6. What is the standard thickness of the disc? 7. What is the limit on deflection of the disc? 8. What precaution would you take before checking for deflection of disc? 9. Give the functions of the piston seal.

Overhaul of Rear Drum Brakes

For description of hydraulic drum brakes refer section 4.2.2 of CAF 101.

Removal of Rear Brake Drum and Back Plate

Loosen the rear wheel nuts.

Lift the car up with the hydraulic garage jack.

Unscrew the wheel nuts.

Remove the wheel.

Place a safety stand under the axle.

Lower the jack and remove it from under the car.

Remove the spindle cap at the drum with a screw driver.

Remove the split pin.

Unscrew the axle castle nut with a socket and handle.

Fix the brake drum remover to the drum with two nuts.

Pull the brake drum remover with a sliding hammer until the drum is removed from the axle.

Unscrew the two nuts and remove the drum remover from the drum.

Unscrew the bleeding nipple and remove it.

Unscrew the flare nut.

Remove the brake pipe.

Loosen the four nuts holding the axle to the back plate with a spanner and then unscrew them completely.

Lift off the back plate.

Dismantling Back Plate and Wheel Cylinder

Turn the shoe hold-down pin to release the shoe hold-down spring and remove the spring.

Remove the other hold-down spring.

Pull the two brake shoes outwards to disengage them from the wheel cylinder.

Lift off the two brake shoes from the back plate.

Remove the boot of the wheel cylinder from one side.

The piston and the spring also

come out along with the boot of the wheel cylinder.

Remove the other side boot along with the piston.

Remove the piston seal from the wheel cylinder piston.

Unscrew the two bolts holding the wheel cylinder to the back plate.

Remove the wheel cylinder from the back plate.

The various parts of the brake

shoes are dismantled next.

Fig. 4.4: Back plate assembly.

Fig. 4.7: Brake shoes, brake strut and

shoe return spring.

Fig. 4.5: Wheel cylinder.

Fig. 4.6: Wheel cylinder piston.

Remove the first shoe return spring.

Remove the brake strut and the second shoe return spring from one brake shoe so that the two brake shoes are separated.

Remove the shoe return spring, the strut and the rod spring from the second brake shoe.

Inspection of Parts

The various parts of the drum brake system are the brake drum, the wheel

cylinder body, spring, piston, boot, piston seal, brake shoes, shoe return springs, brake strut, and shoe hold down springs and pin, and the back plate.

Check each brake shoe lining for wear. If the thickness of the brake shoe rim and lining is less than the service limit of 2.6 mm, the shoe should be replaced. The standard thickness is 6.0 mm.

Inspect the return spring hook ends for breakage.

Inspect the shoe hold-down spring and the pin for breakage or damage.

Inspect the bore of the wheel cylinder. It should be smooth and shiny and should not have scratch marks.

Check the other parts of the wheel cylinder.

Inspect the pistons and the dust boots for wear or damage.

Inspect the spring for breakage or weakening.

Inspect the inner surface of the drum for cracks, scoring marks, and deep groove lines. Further, it should not be excessively worn. The standard inner diameter is 180 mm and the wear limit is 182 mm.

Assembly of Wheel Cylinder

Clean the components of the wheel cylinder with brake fluid before assembly.

Apply brake oil to the seal and install it in the piston.

Push the piston in the wheel cylinder.

Fix the boot on one side.

Fix the spring to the other piston and push it in the wheel cylinder.

Install the other rubber boot on the side.

Insert the wheel cylinder in the back plate.

Fix the wheel cylinder to the plate with two bolts and tighten the bolts fully.

Screw in the bleeding nipple in the wheel cylinder.

Assembly of Back Plate

Fix the brake strut in the shoe.

Fix the rod spring between the shoe and the strut.

Fix the hook of the bolt in the other shoe.

Insert the stud in the brake strut.

Fix the shoe return spring properly below the brake strut.

Fix the toes of the brake shoes in the notch in the pistons of the wheel cylinder. If the notch is not properly aligned with the brake shoe, it should be rotated as required.

Fix the other shoe return spring.

Fix the ends of the brake shoes in the anchor plate.

Insert the shoe hold-down pin from the back side of the back plate.

Place the shoe hold-down spring over the brake shoe.

Turn the pin to lock the spring.

Fix the other hold down spring.

Mounting the Rear Wheel

Mount the back plate on the rear axle and screw in the flare nut of the flexible brake pipe in the wheel cylinder threaded hole.

Place the washers and screw in the four nuts on the screws of the back plate.

Tighten the flare nut and then tighten the nuts of the back plate.

Screw in the bleeding screw in the wheel cylinder.

Mount the drum on the axle, place washer, and then screw in the castle nut.

Tighten the nut with a socket and torque wrench between 8.0 to 12.0 mkg.

Insert the split pin and bend it properly.

Install the spindle cap and tap it lightly with a plastic hammer to fix it properly.

Mount the wheel and screw in the four wheel nuts.

Tighten the nuts with a wheel spanner.

Lift the car with a hydraulic garage jack and remove the safety stand.

Lower the jack and remove it form under the car.

Tighten all the four wheel nuts fully.


10. What is the function of the wheel cylinder? 11. What is the function of brake strut? 12. What is the standard thickness of the brake shoe rim and lining, and what is the

service limit? 13. What is the standard inner diameter of the brake drum and what is the service limit?

Activity

1. Study the layout and working of disc brakes of a motorcycle.

Summing Up

Disc brakes are used in the front because they provide better stability due to uniform pressure distribution and less effect due to increased temperature. Their layout and construction is different from drum brakes. They are also self-adjusting. In some cars, disc brakes are used in both the front and rear wheels.

While using brake drum remover and sliding hammer, care should be taken that fingers do not get caught between the stopper and the dead weight of the hammer otherwise it will give a nasty blow.


1. U-shaped housing that contains the hydraulic piston(s) and holds the pads in disc

brake applications. 2. Banjo bolt is a special type of bolt with drilled passages at 90O and which is used

in conjunction with a special type of tube having a channel adapter for delivering fluid smoothly and not in the form of a jet.

3. compressed air is blown into the cylinder through the hole of the banjo bolt 4. A clean cloth should first be placed in front of the piston before blowing the air, so

that the piston does not get damaged when it comes out 5. standard thickness is 15.5 mm and the wear limit may be specified as 6.5 mm or

8.5 mm depending on design 6. standard thickness of the disc is 10 mm and the wear limit is 8.5 mm 7. limit on deflection is 0.15 mm 8. Before checking for deflection, it should first be ensured that the front wheel

bearing is not loose 9. piston seal is used to provide a liquid-tight seal between the piston and the

cylinder and it also helps to adjust the clearance between the pad and the disc automatically when they get worn

10. Pushes the brake shoes out to contact with the drum 11. Adjust brake drum clearance on wear 12. The standard thickness of brake shoe rim & lining is 6.0 mm and the service limit

is 2.6 mm. 13. standard inner diameter is 180 mm and the wear limit is 182 mm

Terminal Questions

1. Describe the working of the front brake caliper. 2. List the parts of the rear drum brake and give the function of each

References

1. Maruti 800 Service Manual

Glossary

Back plate Steel plate upon which the brake shoes are mounted.

Banjo bolt A special type of bolt with passages at 90O and which is used in conjunction with a special type of tube having a channel adapter for delivering fluid smoothly and not in the form of a jet.

Bleeding nipple, bleeder screw

Valve in wheel cylinders (and other locations) for bleeding air from the hydraulic system.

Brake lining Friction material fastened to the brake shoes.

Brake shoe Part of the drum brake to which the brake lining is attached.

Brake strut Tension rod used to adjust brake drum clearance automatically.

Caliper U-shaped housing that contains the hydraulic pistons and holds the pads on disc brake applications.

Flare nut Nut which is used to connect a fluid joint with the help of a tube flared at the end; the flared end seats on a mating seat.

Steering knuckle Inner portion of the spindle that pivots on the king pin or ball joints

Braking System 103

Documents

Transcript of Braking System 103