Chery A15. Manual — part 211

Figure: Structure of Rear Wheel Drum Brake

1-Brake back plate 2-Pin roll 3-Retracting spring 4-Brake shoe positioning spring

5-Push rod 6-Parking brake arm drag 7-Brake shoe and arm drag assembly 8-Bracket

9-Support plate 10-Rivet 11-Lower retracing spring 12-Tension spring 13-Check hole

14-Pressure spring 15-Clamp pin 16-Spring seat

17-Brake shoe and toothed wedge regulating plate assembly 18-Friction lining

19-Wedge regulating plate 20-Wedge regulating block 21-Brake wheel cylinder

1. Structure of Rear Wheel Drum Brake

Brake back plate 1 is fastened on rear axle flange end. Brake wheel cylinder 21 is

fixed on back plate, and bracket 8 and support plate 9 are fixed under back plate with

rivet 10. The upper end of brake shoe ventral shield is supported in the slots on both

sides of wheel cylinder, and the lower end is borne by support plate 9. Clamp pin 15,

spring seat 16 and pressure spring 14 together press the brake shoe onto the bearing

plane of brake back plate to avoid axial displacement of brake shoe. Float bearing of

brake shoe allows it to float a little along brake wheel cylinder piston plane and

bearing plane of support plate, and the self-centering function of brake shoe ensures

the full face contact of brake shoe and brake drum. Wedge regulating plate 19 on

brake shoe and toothed wedge regulating plate assembly works with wedge regulating

block to adjust clearance between shoe and brake drum. Parking brake arm drag 6 is

able to swing around pin roll 2. The small hook slot in the lower part of parking brake

arm drag 6 is used to hook the end of parking brake dragline. Friction lining 18 is

riveted on the working surface of brake shoe. Lower ends of both brake shoes are

tightened by lower retracing spring 11, and upper ends are tighten by brake shoe

positioning spring 4 and secondary retracing spring 3.

2. Operation of Rear Wheel Drum Brake

When braking, brake wheel cylinder piston pushes brake shoe by the force of brake

fluid to rotate it outward around the contact point of brake shoe and support plate,

thus pressing the friction disk of brake shoe onto brake drum to produce brake torque

and finally achieve vehicle braking.

When the brake is released, brake shoes return to their original positions with the help

of retracting spring 3, 4 and 11 after the brake pressure disappears.

Braking clearance of rear brake is self-regulated. In case the braking clearance

exceeds set value due to shoe plate wear, wedge regulating block 20 located between

lever and brake shoe will be pulled down by tension spring 12 to compensate the

increased clearance between lever and wedge regulating block, and brake shoe will be

opened wider toward brake drum to compensate worn part of friction disk.

IV. Parking Brake

Parking brake is realized by adding a hand operating control mechanism on rear

wheel brake. As shown in the figure below, parking brake shares the same brake with

rear wheel brake, thus simplifying the structure and reducing the weight.

2

1. Brake handle 2. Drawbar 3. Adjusting nut
4. Locknut (8Nm) 5. Compensation rod 6. Nut (20Nm)
7. Parking brake dragline 8. Parking brake dust cover assembly

Installation and adjustment of parking brake system (as shown in the figure above)

Fit tightly the dust cover assembly on parking brake control mechanism, and lock the

mechanism assembly onto the welded screw on vehicle body, tightening torque is .

(only applicable to BMW engines)

1. Parking brake dragline is connected to compensation rod through hand brake sleeve

(fixed on vehicle body) and parking brake dragline conduit, and then fixed on bottom

of vehicle body by bracket clamp, brake line lock thread and dragline hanger

assembled on rear axle.

2. Connect parking brake dragline and compensation rod with adjusting nut and

locknut, tightening torque is 9±3Nm.

3. Fix the drawbar of parking brake control mechanism assembly to compensation rod,

and then turn it 90º to fix it on vehicle body.

4. Parking brake controls rear wheel brake through the dragline.

V. Vacuum Booster and Brake Master Cylinder

A15 series adopt 228.6mm (9in) vacuum booster and tandem type brake master

cylinder for brake assistance, which is realized by vacuum produced by working

engine. Vacuum chamber of the booster is connected with air intake pipe of engine

through vacuum tube and check valve.

Tandem type brake master cylinder consists of cylinder body, piston, spring, spring

seat, rubber cap, etc. Brake master cylinder is connected with fore end of booster by

two bolts. A brake fluid tank is fixed on brake master cylinder, which includes two

serial working chambers (primary chamber and secondary chamber).

Main technical parameters of A15 car brake system:

Brake master cylinder: φ22.2mm

Vacuum booster: Φ228.6mm（9in）

Vacuum booster boost ratio: 3.9:1

Primary chamber travel: 16 mm

Secondary chamber travel: 18 mm

Front wheel disk brake: wheel cylinder diameter: Φ54mm

Brake disk outer diameter: Φ256mm

Brake disk thickness: 13mm

Front friction shoe thickness: 14mm

Rear drum brake: brake drum diameter: Φ200mm

Rear drum brake wheel cylinder diameter: Φ17.46mm

Rear drum brake shoe plate: Φ200mm×40mm×5mm

Brake power distribution ratio: front wheel 65%, rear wheel 35%

Parking brake: acting force of parking brake control handle (38mm from end) <

400N with 20% full load on ramp

Section Two: Maintenance of Brake System

I. Disassembly/Assembly and Inspection of Front Wheel Disk Brake

(I). Disassembling/Assembling Disk Brake

1. Disassemble Steps

(1). Lift the car and demount front wheel.

(2). Loosen and remove tightening bolt (where

the arrow points)

(3). Take off brake caliper shell and brake shoes.

2. Assemble Steps

Assemble sequence is reversed from disassemble

sequence. Attention shall be paid to the following:

(1). Brake shoe with a larger friction surface shall

be installed outside.

(2). Brake shoes on both sides shall be replaced at

the same time, and replacing ones shall be

manufactured by the same one supplier.

(3). Tightening torque of fastening bolt is 25Nm

(as shown in the figure)

(4). Tightening torque of wheel bolt is 110Nm.