Foton Series Light Bus. Instruction — part 15

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Figure 10-8-1 Front Disc Brake

1-Assembly of left disc brake; 2-Assembly of right disc brake; 3-Left steering knuckle arm; 4-Right steering knuckle arm;

5-Left steering knuckle; 6-Right steering knuckle; 7-Ball spigot assembly; 8-Left dust cover assembly; 9-Right dust cover assembly;

10-Bolts for installation of pitman arm; 11-Hexagon bolt; 12-Split pin; 13-Ball spigot nut; 14-Split pin; 15-Nut; 16-Connecting bolt

for arrestor; 17- Flat gasket; 18-Left stop pliers assembly; 19-Right stop pliers assembly; 20-Tong holder; 21-Silencer; 22-Supporting

spring

for friction plate

Ⅰ

; 23-Stop friction plate assembly; 24-Alarm; 25-Supporting spring

for friction plate

Ⅱ

; 26-Split pin;

27-Dust cover for guide sleeve; 28-Long guide sleeve; 29-Long shaft guide sleeve; 30-Air bleed bolt; 31-Dust cover for air bleed bolt;

32-Steady ring; 33-Dust cover for piston; 34-Piston for sub-pump; 35-Seal ring for piston; 36-Left stop plier; 37-Right stop plier;

38-Fixed bolt for short guide sleeve; 39-Short guide sleeve; 40-Short shaft bushing; 41-Brake disk; 42-T-type oil seal; 43-Taper roller

bearing; 44-Bolt for front wheel hub; 45-Front wheel hub; 46-Bolt subassembly; 47-Taper roller bearing; 48-washer; 49-Nut;

50-Adjusting lock blade; 51-Cotter pin; 52-Cover for front wheel hub

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Figure 10-8-2 Rear Drum Brake

1-Left rear brake assembly; 2-Right rear brake assembly; 3-Spring seat; 4-Stop pull-out piece spring; 5-Stop extension spring;

6-Rear stop brake; 7-Left upper release spring; 8-Right upper release spring; 9-Left self adjusting turn buckle; 10-Right self adjusting

turn buckle; 11-Left self – adjusting ratchet wheel; 12-Right self-adjusting ratchet wheel; 13-Self – adjusting gasket; 14-Self –

adjusting sleeve; 15-Left front brake shoe; 16-Right front brake shoe; 17-Steel jacket for brake; 18-Pull rod for left brake; 19-Pull rod

for right brake; 20-Split baffle ring; 21-Split baffle ring; 22-Self – adjusting bolt (left); 23-Right – adjusting bolt (right); 24-Spring;

25-Braket of rocker arm; 26-Rocker arm cover; 27-Rocker arm (left); 28-Rocker arm (right); 29-Spring; 30-Hexagon head bolt with

cross channel; 31-Hexagon thin nut; 32-Clevis pin with head; 33-Split baffle ring; 34-Light type spring washer; 35-Hexagon bolt

with full thread, Grade C M18×16; 36-Rear soleplate assembly (left); 37-Rear soleplate assembly (left); 38-Rubberized stop;

39-Pull rod for pull–out piece spring; 40-Hexagon bolt with full thread M8×16; 41-Light spring washer; 42-Rear brake subpump

assembly; 43-Dust cover; 44-Piston assembly; 45-Leather cup; 46-Spring; 47-Cylinder body; 48-Bleed valve

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Figure 10-8-3 Parking Brake Control System

1-Front parts assembly for hand brake; 2-Handle assembly; 3-Jacket for hand brake joy stick; 4-Jacket assembly for hand brake

joy stick; 5-Support sleeve; 6-Pin; 7-Pin shaft; 8-Pulley; 9-Split pin; 10-Clip/card; 11-Front pull wire assembly; Assembly for front

hose with joint; 12-Hexagon bolt, spring washer and flat washer set; 13-Hexagon bolt, spring washer and flat washer set;

14-Assembly of hand brake’s operating arm with support; 15-Assembly of hand brake’s operating arm; 16-Bushing; 17-Inner sleeve;

18-Flat washer; 19-Hexagonal nut type 1 ; 20-Rocker arm support; 21-Hexagon bolt; 22-Hexagon bolt, spring washer and flat washer

set; 23-Adjusting nut for operation of hand brake; 24-Spring of rocker arm for hand brake operation; 25-First support assembly for

back pull wire; 26-Hexagon bolt, spring washer and flat washer set; 27-Upper cover board; 28-Hexagon bolt and flat washer set;

29-Second support assembly for back pull wire; 30-Hexagon bolt, spring washer and flat washer set; 31-Hexagon bolt, spring washer

and flat washer set; 32-Back assembly for hand brake operation; 33-Hexagon bolt, spring washer and flat washer set; 34-Pin shaft;

35-Flat washer; 36-Split pin; 37-Front hose clip (1); 38-Hexagon bolt, spring washer and flat washer set; 39-Front hose clip (2);

40-Card; 41-Support for front pull wire; 42-Hexagon bolt, spring washer and flat washer set; 43-Jointing sleeve for second support of

back pull wire; 44-Hexagon bolt, spring washer and flat washer set; 45-Bolt shaft; 46-Rubber sleeve; 47-Spring gasket;

48-Hexagonal nut type 1 ; 49-Hexagon bolt and flat washer set; 50-Assembly of balancer support; 51-Hexagonal nut type 1 /spring

washer; 52-Jointing sleeve for second support of back pull wire

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Figure 10-8-4 Vacuum Booster with Brake Master Cylinder Assembly

1-Fluid feeding joint; 2-O–shaped ring; 3-Cylinder; 4-Vacuum booster; 5-Pushing bar fork for controlling; 6-Hexagonal nut type

1 M1×1.5; 7-Steel belt type of small hoop; 8-Oil feeding hose of base pump; 9-Cup assembly; 10-Filtering net assembly; 11-Oil cup

lid; 12-Bowl type of auxiliary part; 13-Spring retainer ring type A 28; 14-Rear piston; 15-Master bowl; 16-Spring seat; 17-Back

spring; 18-Front spring; 19-Elasticity stop collar type A for shaft; 20-Front spring

10.8.2.2 Brake System Service

10.8.2.2.1 Check and Repair Brake System

1. Check and adjustment
① Brake pedal height. The height from the floor should be 155~165mm. Adjust he height as indicated in

figure 10-8-5.

Figure 10-8-5 Check Brake Pedal Height

Push rod
of pedal

Switch of
parking light

Height

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② Brake pedal free travel. Step down the brake pedal until some resistance is felt. The free travel should be

5~10mm. As shown in figure 10-8-6.

Figure 10-8-6 Check Brake Pedal Free Travel

③ Check the margin distance of pedal travel. Release parking brake instruction handle while engine is running,

step down the brake pedal. The margin distance of pedal travel is as shown in figure 10-8-7. Under 490N stepping

force, the distance is more than 58mm. If the distance is incorrect, perform diagnosis for the brake system.

Figure 10-8-7 Check Brake Pedal Margin Travel

2. Test vacuum booster
① Before starting the engine, step down the brake pedal for several times. Check brake pedal for the stroke

margin and make sure it has not changed.

② Step down the brake pedal and start the engine. If the pedal drops slightly, it is in good condition.
③ Start the engine and shut it down after 1~2 minutes. Step down the brake pedal slowly for several times.

If the travel for the first application is the longest while afterward applications decrease gradually. This indicate

the vacuum booster is sealed well.

④ When the engine is running, step down the brake pedal and shut down the engine. If the pedal travel

margin does not change in 30 seconds, it indicates a well sealed vacuum booster.

3. Brake system bleeding. Discharge air for the brake system in following situation: the brake system has

Push rod
of pedal

Switch of
parking light

Free travel of
pedal

Margin distance of
pedal travel

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been disassembled and re-installed, or brake system is suspected to have air in its pipeline,

4. Check and adjustment of parking brake lever travel
① Slowly pull up the parking brake lever with a force of 200N. If 18~20 clicks are heard, the parking brake

is adjusted correctly. Otherwise adjust it.

② Before adjustment of parking brake, adjust the clearance between rear brake lining and brake drum.

Adjust the travel of parking brake lever by the adjusting nut.

10.8.2.2.2 Repair brake master cylinder
① After disassembly and cleaning brake master cylinder parts, use compressed air to dry them up.
② Check the cylinder tube inner wall for rust or scratch.
③ Replace if wear or damage is present on the cylinder.
④ Check piston and sealing ring for scratch and replace if necessary.
⑤ After installation of brake master cylinder, adjust the length of push rod before it is installed onto the

vacuum booster.

10.8.2.2.3 Repair front disc brake
① Check brake lining thickness through the check hole. The normal thickness is 10mm and the minimum

thickness is 1.0mm. If its thickness is not within the specified range, replace the friction lining.

② The nominal thickness of brake disc is 25mm and its wear limit is 22.5mm.
③ Measure the radial run out within 10mm from brake disc edge. If the radial run out is more than 0.12mm,

replace with a new one.

④ The maximum increment of cylinder tube should not exceed 0.05mm.

10.8.2.2.4. Repair rear drum brake
① If the thickness of brake lining is less than 1mm, replace with new one.
② The nominal inner diameter of brake drum is 254mm and the maximum inner diameter is 256mm.
③ Scratch or wear on brake drum can be corrected by fine grinding with lathe.
④ The contact area of brake lining with brake drum should be more than 70%; otherwise perform polishing

process.

⑤ If the distance from the surface of brake lining to rivet head is less than 0.8mm, replace brake pad.

10.8.3 Check of Brake Performance of Vehicle

Test braking performance on a brake tester. Drive the vehicle onto tester’s check platform and check

respectively the weights of front axle and rear axle. Then, drive the vehicle onto the brake tester and put it straight.

Operate the test in accordance with the equipment operation instruction. Only one technician is allowed to be

inside the vehicle.

Table 10-8-1 Checklist for Brake Performance

Ratio -- front axle brake force to axle load (%)

≥60%

Ratio -- left and right difference of front axle(%)

≤15%

Ratio --left and right difference of rear axle (%)

≤20%

Ratio -- the max braking force difference to rear

axle load (%) (when rear braking force is less than

60% of rear axle load)

≤7%

Brake

performance test

Ratio-- sum of parking brake force to gross vehicle

weight (%)

≥20%

Ratio-- total brake force to vehicle total mass (%)

≥60%

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Remarks:
① No brake running-in is allowed on the braking platform. If hand brake rachet tooth number is more than

24, the control cable is too long and need to be adjusted.

② When measuring the brake, in order to obtain enough adhesive force to avoid wheel lock, it is allowed to

put wedges under the wheels that are not under checking.

③ When to check braking performance of BJ6486、BJ6516 series light buses on concret road at a speed of

30km/h, its braking distance should be ≤8m and error should be less than 60mm. (The stopping distance includes

the factors: driver reaction time, brake system parts mechnical transferring time and braking force actuating time.)

④ Parking brake unit creates required braking performance when it operates within 2/3 travel of operating

devices.

10.8.4 Typical Faults and Troubleshooting

1. Typical faults and troubleshooting for driving brake system

(1) Brake failure, see Table 10-8-2.

No braking force when brake pedal has been depressed consecutively.

Table 10-8-2 Brake Failure

Causes

Solutions

1． Brake fluid short or no fluid in master cylinder

2． Worn-out master cylinder or damaged master/wheel

cylinders cups

3． Broken brake pipeline or damaged connector

4． Master cylinder push rod pin is detached

1． Add fluid to standard

2． Replace

3． Repair or replace pipeline

4． Re-mounting

(2) Ineffective brake, see Table 10-8-3

Depress brake pedal cannot stop vehicle timely, and consecutive depressing shows no good result either.

Table 10-8-3 Ineffective Brake

Causes

Solutions

1． Air in brake pipeline or fluid leakage

2． Excessive pedal free travel

3． Excessive clearance between drum and pad

4． Brake cup expands to stick

5． Excessive pad lining wear, poor contact or oil dirt on it

6． Drum out-of-round, incorrect friction coefficient

7． Aged brake hose to inflate

1． Bleeding, remove leakage

2． Adjust pedal free travel

3． Adjust clearance

4． Replace cup

5． Grind or replace pad

6． Repair or replace drum

7． Replace hose

(3) Brake bias

Braking forces on both sides are not even or synchronizing, this makes vehicle driving to one side

Table 10-8-4 Brake bias

Causes

Solutions

1. Pad clearances on both side are not even

2. Certain hose/connector clogged, or air in pipeline

3. Certain brake cup expands to stick

4. Certain pad has oil dirt or becomes worn-out, rivet

1． Adjust clearance

2． Remove restriction or bleed system

3． Replace cup

4． Abrasive pad or replace

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Causes

Solutions

exposed

5. Uneven tyre pressures on LH/RH tyres

6. Certain drum is out of round

7. Drums become distort after rim covers have been installed

8. Different friction coefficient on RH/LH drums

9. Brake lag—RH/LH

10. Vehicle frame distortion, wheel base unparallel

5． Inflate tyre to standard

6． Repair

7． Measure and check after installing

rim cover, grinding if necessary

8． Replace with drums of same

coefficient

9． Locate cause and adjust

10． Measure and adjust

(4) Brake drag (drum overheating)

Release brake pedal cannot cancel braking timely while drum temperature increases. Normal drum working

temperature should be not 70℃ more than ambient temperature ( the value might be higher during long hill drive

in mountain area). In order to find the cause of drum overheating, one can either test vehicle’s coast distance or

driving without braking.

Set off an unloaded vehicle to coast on paved and dry road at initial speed of 30km/h. At the time the vehicle

stops completely, for ordinary vehicle, the coast distance (average value of two round tests) should not be less

than 220m, and 180m for front drive vehicle. If drum contacts pad, the distance will be shortened and drum

heated.

Drive vehicle for 3-5km, if drum becomes very hot, this may due to causes like pad contacts drum, wheel

hub bearing is loosing or rear axle case is bend etc. One can make further check by jacking up vehicle on the hot

drum side and turning the wheel. If pad does not contact drum, the symptom may due to loose wheel hub bearing

or warped rear axle case.

① Brake drags on all wheels simultaneously, see table 10-8-5.

Table 10-8-5 Brake drags on all wheels simultaneously

Causes

Solutions

1． Master cylinder returns slowly

2． Short pedal free travel

3． Clogged pipeline, restricted fluid return

1． Repair master cylinder

2． Adjust free travel

3． Clear pipeline

② Brake drag on certain wheel, see table 10-8-6.

Table 10-8-6 Brake drag on certain wheel

Causes

Solutions

1. Smaller clearance — drum to pad

2. Weak shoe return spring

3. Wheel cylinder cup inflated or piston stuck

4. Brake hose inflated and choked

1. Adjust clearance

2. Replace spring or adjust supporting

pin and eccentric

3. Repair or replace

4. Replace hose

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(5) Braking noise, see table 10-8-7.

One can hear squeak at braking or intermittent rubbing sound.

Table 10-8-7 Braking noise

Causes

Solutions

1． Drum out-of-round or uneven wear

2． Dirt pad or un-secure riveting

3． Shoe contacts drum

4． Excessive pad wear, pivot end contacts drum

1． Repair or replace drum

2． Grinding or remount rivet

3． Repair and adjust

4． Replace shoe/pad assembly

(6) Brake pedal drops gradually, see table 10-8-8.

During braking, the pedal may drops to the floor suddenly. Step on repeatedly cannot make it returning.

Table 10-8-8 Brake pedal drops gradually

Causes

Solutions

1． Brake pipeline leakage or air in the system

2． Worn-out master cylinder cup and ring, fluid leaks at

braking

3． Wheel cylinder cup reversed

1． Repair and bleeding

2． Repair and replace parts

3． Repair

(7) Brake pedal goes up gradually, see table 10-8-9.

Pedal goes up gradually after it has depressed repeatedly during driving.

Table 10-8-9 Brake pedal goes up gradually

Causes

Solutions

1． Master cylinder fluid compensation hole blocked

or sealing ring covers the hole, excessive fluid can

not flow back to fluid cup

2． Smaller free clearance — master cylinder piston

push rod

3． Air in brake system

1. Clear compensation hole or readjust

2. Readjust

3. Bleeding.

(8) Too heavy brake pedal, see table 10-8-10.

Due to ineffective Due to vacuum booster failure, brake pedal becomes heavy without well braking force.

Table 10-8-10 Too Heavy Brake Pedal

Causes

Solutions

1． Diaphragm air leak or broken spring — vacuum booster

2． Diaphragm fluid leak — control valve

3． Vacuum valve ajar — control valve

4． Vacuum hose air leak

5． Check valve failure

1． Repair damaged parts in vacuum

booster

2． Repair damaged parts in vacuum

booster

3． Repair damaged parts in vacuum

booster

4． Replace hose or tighten connectors

5． Replace check valve

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2. Typical Faults and Troubleshooting for Parking Brake System

Ineffective hand brake, see table 10-8-11.

Lift instruction brake handle cannot stop vehicle from coasting.

Table 10-8-11 Ineffective Hand Brake

Causes

Solutions

1． Parking brake cable is too long

2． Larger clearance between pad and drum or they contact

poorly

3． Worn-out pad, rivet exposed

4． Dirt on pad or on drum

1． Readjust

2． Readjust

3． Replace pad

4． Remove dirt with sand paper

Tips: Test whether drum heating is normal or not:

Drive vehicle on nice and plane road for 10km. Apply brake normally. Touch brake drum with hand. If

temperature is endurable, break drum heating is in normal range;
● Notes:

1. Above case allows temperature difference between FR/RR, RH/LH drums.

2. If drums become scalding after several emergency braking, the high temperature do not

warrant that drum heating is out of normal range.

10.9 Wheel

10.9.1 Main Technical Parameters of Wheel

Main Technical Parameters of Wheel

Sn

Description

Data

1

Type of wheel

Tubeless

2

Type of wheel rim

6 x14 wheel rim with a offset distance of 30mm

Type

Web type

3

Spoke

Center diameter of bolt

hole (mm)

5 holes, distribution circle φ114.3; diameter of bolt hole

φ15±0.3; center hole φ64＋05＋02＋05＋02

＋05

＋02

Type

Radial ply tire

Dimensions

195/70R15C and 185R14C

Air pressure of front

tires (kPa)

325 (for 205 tire, 250)

4

Tire

Air pressure of rear tires

(kPa)

450 (for 205 tire, 250)

5

Wheel nut

Tightening torque

Tightening torque for steel wheel hub nut is 105±5N.m

Tightening torque for aluminum alloy wheel hub nut is

120±5N.m

6

Total

tire

body

Amount of dynamic

balance (add counter

weight onto wheel rim)

710gram-cm (300rpm)

10.10.2 Structure Overview

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Vehicle’s driving performance is closely related to wheels and tires. Wheels and tires are used to support

vehicle body, alleviate impact force from road, and receive and transmit braking and driving forces. Meanwhile,

tyre helps to resist side skipping, and wheel by itself can return to straight line automatically, ensuring vehicle to

make a turn and drive in straight line.

BJ6536 series light buses adopt tubeless tire (see figure 20-10-1). The tire has no inner tube. Air is directly

injected through valve into outer tire. It requires good sealing performace between rim and outer tire. Tubeless tire

looks the same as an ordinary tire, but a rubber sealing lining (2-3mm) applied on inner wall of outer tire makes

the difference. Lining application is made by means of sulfurization. On lining’s inner surface, there is layer of

self-adhesive composite that can mend any possible pierce-through on tire. There are several concentric circular

grooves on tire, which help tire edge to press closely on rim under air pressure inside tire, thus closed air sealing

between tire and rim is guaranteed.

Valve is directed mounted on rim with rubber gasket for sealing. Rivet used to connect web and rim extends

out from inside with sealant. Vacuum tire pressure will not lower abruptly after tire has been pierced through,

which guarantees a safe driving. By using tubeless tire, there are no friction and stuck between inner tube and tire,

and heat created can be emitted through rim directely. Tubeless tire’s life span is longer plus it is simple structured

and light in weight. But tubeless tire is difficult to repair in the midway, and self-adhesive lining works only when

tire is pierced through. In hot weather, the lining is prone to be melted and may flow downward, interrupting

dynamic balance. Therefore, some vehicles adopt tubeless tire that has no adhesive lining, its inner wall has only

compressed seal lining. Compressed lining will press tightly around any possible piercing object, and keep tire

prssure for quite a while even the object is removed. In this case, this type of lining partly performs the function of

self-adhesive type lining.

Figure 10-10-1 Tubeless Tire

1-Rubber sealant; 2-Self adhesive material layer; 3-Groove; 4-Tire valve; 5-rivet;

6-Rubber seal pad; 7-Wheel Rim.

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Figure 10-10-2 Wheel and Tire

1-Wheel assembly; 2-Tire; 3-Wheel rim counter weight; 4-Wheel hub nut;

5-Wheel rim assembly; 6-Valve of tubeless tire

Figure 10-10-3 Spare Tire Installation Mechanism

1-Weldingon assembly of spare tire bracket (1); 2-Hexagon bolt; 3-Pressure plate; 4-Hanger assembly;

5-Weldingon assembly of spare tire bracket (2)

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Crown Tire crown refers to center section between tire shoulders. Tire tread refers to crown’s most outer

layer (with pattern) that contacts road; baffle layer refers to fabric layer between diagonal tire tread and body, it

helps to alleviate and absorb partially impact to tire from road; belt layer refers to the layer clamping tire body

circularly along tread center line (for radial ply and bias belted tire), it helps to strengthen tire’s circular and side

stiffnesses and take most of the tread force; cord layer refers to rubber fabric composed by parallel cord in center

tire body, it is the skeleton of tire body and it supports each part of outer tire.

Tire sidewall refers to the rubber layer on lateral wall of carcass between tire shoulder and tire bead. It

protects tire carcass and takes force from sides

Tire bead Bead refers to the part that contacts rim. It consists of bead core and bead fabric. It prevents tire

from slipping out of rim.

Wheel rim assembly is made up of wheel rim and spoke, and the spoke is welded on the wheel rim.

Balance weight is to set at unbalance spot during dynamic balance test.

There are two types of tires: bias and radial ply. Radial ply tire as shown in figure 10-1-4 arranges cord with

nearly 90°angle to tread center line. Its name comes after earth’s meridian line. Radial ply tire fully utilizes

cord’s stregthenss, its cord layer number is less than ordinary diagonal tire, and it is light in weight and with soft

tire body. Radial ply tire uses multi-layer belt with small tread center line angle (10～20°), is made of cord or

wire cord of high strength and low extension. The tire can take relatively larger tangential force. Belt layer is

closely inset into carcass. It greatly improves tread stiffness, traction and wear-resistance.

Radial ply tire is subject to lower rolling resistance than ordinary diagonal tire is. It helps to save fuel and has

characteristics such as wear-resistance, longer life span, good performance and safety. BJ6536 light bus uses

radial-ply tire.

Mix to use bia and radial ply tires in same vehicle will interrupt vehicle’s drivability. Do not do this!

Figure 10-10-4 Structure of Radial / Bias-ply Tires

1-5 Outer tread; 2-4, 6-Carcass; 3-Belted layer

10.10.2 Technical Specifications and Identifications of Tire

1. Technical specifications: Welding of wheel rim assembly should be firm and secure and no defects such

as included slag, pore and crack etc.. The tires installed on the same vehicle and their tread patterns should be

uniform. Dynamic unbalance is a major cause of direction oscillation of vehicle. The manufacturer of wheel

assembly has performed dynamic balance test for the wheel assembly and counter weights also have been added.

Dynamic unbalance of wheel assembly should be less than 720gram-cm (300rpm, at excircle flank of wheel rim).

2. Identifications of tires

Size marking of outer tube is shown in figure 10-1-5, and the unit is inch.

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Figure 10-10-5 Size Marking of Outer Tube

High pressure tire is denoted like D x B:

D stands for nominal outer diameter of tire, B stands for section width of tire, the unit is inch, and “X” stands

for high pressure tire.

Low pressure tire is denoted like B-d:

B is section width of tire, d is diameter of wheel rim, and “-” stands for low pressure tire. Because section

width B approaches to section height H, so, size of wheel rim to be installed (d) can be calculated by d=D-2B.

Marks of tires fall into British system and metric system.
① Size marking for British system

Generally, ordinary section tires for truck and bias tires for sedans use this kind of mark and it is composed of

the following:

a. Nominal section width of tire, the unit is inch.

b. Structure mark of tire

c. Nominal diameter of wheel rim, the unit is inch.

d. Ply grade

Note: Ply grade refers to the specific strength mark of maximum bearable load on tire. It does not necessarily

indicate the actual number of plies of cord fabric plies. For example: for a tire of “ 9.00 ply grade 12”, it may have

several actual numbers of plies and a maximum load of 2,050kg.

② Size marking for metric system:

Generally, radial tires for sedan use this kind of mark, it includes the following:

a. Nominal section width of tire, the unit is mm.

b. Nominal aspect ratio of tire

c. Speed symbol

d. Structure mark of tire

e. Nominal diameter of wheel rim, the unit is mm.

The nominal aspect ratio refers to the ratio of height and width of section assuming that the tire is installed on

a theoretical wheel rim.

D:Outter diameter d:Inner diameter (i.e. diameter of wheel hub)

R: Width of section H: Height of section

Width of section

Overall width

Width of wheel hub

O

u

tt

er

d

ia

m

e

ter

H

e

igh

t

o

f

sec

ti

on

.

No

m

in

al

d

iame

ter

o

f

wh

ee

l

rim

For
example

The ply grade of tire is 6 (maximum load 635kg, corresponding air pressure 3.50kg/cm

2

)

Nominal diameter of wheel rim (16 inch)

Mark for radial tire

Nominal section width of tire (6.5 inch)

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③ In order to be uniform, International Organization for Standardization (ISO) stipulates that the new size

marking of tire should be composed of the following:

a. Nominal section width of tire, the unit is mm.

b. Nominal aspect ratio of tire

c. Structure mark of tire

d. Nominal diameter of wheel rim, the unit is inch.

e. Load index

f. Speed symbol

10.10.3 Service and Maintenance

Check tire pressure for leakage before driving. Too lower pressure leads to tire heating, higher fuel

consumption and early wear; while too higher pressure leads to vehicle shaking or even tire explosion and also

brings adverse effect to operating stability. Rated pressure for BJ6536 model vehicle is: front wheel 250±10Kpa,

rear wheel 450±10Kpa. Tire surface cannot contact mineral oil (gas, engine oil, gear fluid and lubricants). After

daily driving, one should check tire for any nail pierced, embedded stones in tread. Remove if there are.

Tires of same specification and type should be used in one car, and tires used should match corresponding

model vehicle. In order to keep wear evenly, it is required to rotate wheel regularly (incl. spare tire). Rotation

method see figure 10-10-6.

For
example

Nominal diameter of wheel rim (15 inch)

Mark for radial tire

Speed symbol (210km/h)

Nominal aspect ratio of tire (H/B=0.75)

Nominal diameter of wheel rim (15 inch)

For
example

Speed symbol (210km/h)

Load index (515kg)

Nominal diameter of wheel rim (15 inch)

Mark for radial ply tire

Nominal aspect ratio of tire (H/B≈0.75)

Nominal section width of tire (225mm)

Chapter 10 Chassis Structure and Service

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Figure 10-10-6 Tire Rotation