This document provides an overview of a training module on suspension and retarder systems for buses. The module objectives are to identify different suspension systems used in buses, perform inspection and maintenance on suspensions, and understand retarder systems. The program agenda covers Weveller suspension components and removal/installation, air suspension components and kneeling function, and retarder overview. Practical exercises are included to inspect Weveller suspension and adjust air suspension height.

1. Technician Level 2 (LOB Bus) – Module 5
Suspension & Retarder System

2. Introductions
Please introduce yourself loud and clear including your details for:
 Participant Name
 Dealership Name
 Location
 Experience in Tata Motors (In years & months)
 Hobbies &
 What Bonds you with TATA MOTORS
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3. Program Objective
At the end of this module the participants will be able to:
 Identify the different types of suspension systems used in buses
 Perform inspection and maintenance on the suspension systems
 Perform removal and re-fitment of suspension systems on buses
 Understand the different components and the working of a retarder system
 Perform maintenance and repair on retarder systems
 Perform removal and re-fitment of retarder on vehicle
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4. Program Agenda
 Weveller Suspension
– General Information
– Removal of suspension from vehicle
– Inspection and dismantling of components
– Assembly and installation of suspension
 Air Suspension
– Introduction to air suspension
– Kneeling
– Assembly & Installation of suspension
– Troubleshooting
 Retarder
– General Information
– Working Principle
– Lubrication and Preventive Maintenance
– Removal & Refitment
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5. Weveller Suspension
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6. Introduction
 Weveller spring is a semi elliptical leaf spring without shackle.
 The bush & pin type mounting is replaced by rubber blocks, which insulates shocks.
 This design permits limited longitudinal motion of the spring ends due to rubber blocks at the
ends.
 The spring are suitable for rated load (without overload) for passenger application on good
roads. Due to these constraints, these springs are used in bus application.
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7. Components of Weveller Suspension
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Spring End
End Clip
Spring Hanger Bracket
Bottom Bracket
Rubber Block

8. Components on Vehicle
 Front spring suspension front end
 Front spring suspension rear end
 Rear spring suspension front end
 Rear spring suspension rear end
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9. Exploded View
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Sl.
No.
Description
QT
Y.
Tightening
Torques(kg-m)
01 First Leaf 02 NA
02 Second Leaf 02 NA
03 Third Leaf 02 NA
04 Fourth Leaf 02 NA
05 Fifth Leaf 02 NA
06 Sixth Leaf 02 NA
07 Seventh Leaf 02 NA
08 Eight Leaf 02 NA
09 Ninth Leaf 02 NA
10 Tenth Leaf 02 NA
11 Spring Clip 04 NA
12 Spring Clip 04 NA
13 U Clamp 04 NA
14 Asy. Front Spring 02 NA
15 Guide Plate 02 NA
16 Aux. Clip 08 NA
17 Spacer 08 NA
18 Weweller Rubber (Front
Spring)
08 04
19 Rivet 10X24, IS: 21558 MS 19 NA
20 Spring clip (Weweller) 08 NA
21 Weweller Rubber (Front
Spring)
08 NA
Sl.
No.
Description
QT
Y.
Tightening
Torques(kg-m)
22 Front Spring Hanger BKT
RH Rear & LH FR
04 NA
23 Front Spring Bracket
Lower Cap
04 NA
24 Hex Bolt M 12X85 16 8.5
25 Spacer 04 NA
26 Hex Nut M 20X1.5 16 35
27 Rubber Buffer 02 NA
28 16 8.5
29 Center Bolt 02 12.5
30 Hex. Nut MI0IS:I364 - 8 08 04

10. Tightening Torque
Maintenance / Replacement Checks
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Sr. No. Description Frequency
1
Rubber Quality
Shock absorber for leakage
Cap bolt tightening
At 9000 kms
2
Rubber Change for bad roads
Rubber Change for plain & good roads
At 36000 kms
At 72000 kms
Sr. No. Description Size Torque (kg.m)
1 Fasteners – cap to bracket M12 X 1.75 8.6
2 Spring hanger bracket to frame M14 X 1.5 19.5

11. Instructions for practical exercise
 Trainer:
– Divide the group into 4 teams
– Brief the trainees on the Weveller suspension
components
– Make them inspect each component
 Trainees:
– Follow the instructions of the trainer
– Inspect the Weveller Suspension
 Objective:
– To Inspect the Weveller Suspension
Practical Exercise
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Inspection of Weveller
Leaf Spring Suspension
Components
Duration – 60 Mins

12. Replacement Procedure
For replacing worn out rubber block:
1. Disassemble the shock absorber & brake
hoses.
2. Remove bottom cap with rubber.
3. Jack up the front / rear axle by @ 150 mm.
4. Slip stand under the chassis.
5. Lower the jack to bring spring top rubber
out of top bracket.
6. Clean the spring ends.
7. Locate top rubber block on spring top.
8. Jack up the axle gradually to engage upper
rubber in spring bracket.
9. Locate bottom rubber block on bottom of
spring.
10. Cover bottom cap on rubber block and
engage fasteners.
11. Tighten the fasteners with recommended
torque.
12. Jack up the axle to make stand under the
chassis free.
13. Take out the stand under the chassis.
14. Lower the axle & take out the jack.
15. Assemble the shock absorber and brake
hoses.
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13. Replacement Procedure
For replacement of spring:
1. Disassemble shock absorber & brake hoses.
2. Remove the bottom cap with rubber.
3. Jack up the front / rear axle by @ 150 mm.
4. Slip stand under the chassis.
5. Lower the axle & let tyres touch the
ground.
6. Loosen the ‘U’ bolt & disassemble the
spring.
7. Locate new spring on axle & engage the ‘U’
bolt & nut.
8. Clean up the spring ends & locate top
rubber block on spring top.
9. Jack up the axle gradually to engage upper
rubber blocks in spring brackets.
10. Locate bottom rubber block on bottom of
spring.
11. Cover bottom cap on rubber block &
engage fasteners.
12. Align the spring with spring brackets and
axle.
13. Tighten the ‘U’ bolt nut to hold the spring
with axle without fully tightening.
14. Jack up the axle, to make stand under
chassis free.
15. Take out the stand & lower the jack fully &
take out the jack.
16. Tighten the ‘U’ bolt & cap fasteners with
recommended torque.
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14. Air Suspension System
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15. Introduction
What is Air Suspension?
 A type of suspension that uses air springs instead of conventional leaf springs.
 Mechanically operated Leveling valve allow the system to maintain static ride height and vary
the suspension's ride characteristics.
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Leaf Spring Suspension
Air Suspension

16. Advantages of Air Suspension
 Reduces Vibration.
 Improves ride comfort in seat located in the vehicle.
 Extends a longer life to the body and chassis components.
 Reduces fatigue to the driver.
 Lowers natural frequency to provide a higher ride comfort.
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17. Components of Air Suspension System
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18. Air Spring Assembly
Function: Absorbs shock and provides good ride comfort on all road and load conditions.
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Top Plate
Retaining Plate
Bump Stop
Diaphragm
Piston

19. Control Arm
Function: Controls the movement of the axle in relation to the chassis.
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Compound Link
Parallel Link

20. Levelling Valve Assembly
Function: To maintain constant ride height under varying load and road conditions.
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Brass Elbow
Union Body
Leveling valve
Leveling Valve Lever
Leveling valve connecting rod
Rubber connector sub assembly
Nyloc Nut

21. Anti Roll Bar Assembly
Function:
 The anti-roll bar provides the necessary
vehicle stability (roll stiffness) during
cornering.
 Metalistic bushes and M.R Split bushes
have been incorporated for vibration
isolation.
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22. Shock Absorber Assembly
Function:
 Control suspension movements by
damping suspension system.
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23. Basic Pneumatic Circuit for Air Suspension
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T Joint
NRV
Leveling
Valve

24. Kneeling
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25. Introduction
 Kneeling is the process by which one side of the vehicle (Passenger Door Side) is tilted down
by removing the air in the air springs.
 This is achieved by a electro-pneumatic system.
 The main components in a kneeling system are:
– Relay Valve
– Relay Inversion Valve
– Magnetic Valve
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Relay Valve Relay Inversion Valve Magnetic Valve

26. Kneeling Circuit
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Note: The following slides have to be explained by the trainer

27. Kneeling Circuit – Normal Operation
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28. Kneeling Circuit – Parking Brake ON
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29. Kneeling Circuit – Rear Left Kneeling ON
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30. Kneeling Circuit - Rear Left Kneeling OFF
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31. Assembly & Installation of Suspension
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32. Instructions for practical exercise
 Trainer:
– Divide the group into 4 teams
– Brief the trainees on the Assembly procedure and
the Do’’s & Don'ts
– Make them assemble the bellow & piston
 Trainees:
– Follow the instructions of the trainer
– Assemble the bellow & piston
 Objective:
– assemble the bellow & piston
Practical Exercise
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Assembly of bellow &
piston
Duration – 60 Mins

33. Instructions for practical exercise
 Trainer:
– Divide the group into 4 teams
– Brief the trainees on the procedure for Static height
adjustment
– Make them adjust the Static height
 Trainees:
– Follow the instructions of the trainer
– Adjust the static height
 Objective:
– To adjust the static height
Practical Exercise
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Static height adjustment
Duration – 60 Mins

34. Retarder
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35. Introduction
 Retarder is an auxiliary, frictionless braking device, which serves to slow down vehicle’s speed
or maintain steady speed when moving downhill.
 It is usually not capable of bringing vehicle to a standstill, as its effectiveness diminishes at
low speed.
 It is usually used to slow vehicle’s speed down, with the final braking being carried out by a
friction (service) brake.
 As the friction brake does not then need to be used so much, particularly at higher speed, the
service life time of friction brake and tyre is increased.
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36. Salient Features of the Retarder
 It is a frictionless, secondary braking system.
 It drastically reduces the use of service brakes - thereby enhances economy of operation by
improving life of brake lining, brake drum and tyre.
 It provides downhill cruise control – smooth downhill endurance braking, more comfort,
safety and shorter journey time (by maintaining constant speed).
 It protects the environment by significantly reducing the amount of dust produced by the
wearing of brake lining.
 It also contributes reduction in noise pollution levels in urban area, associated with brake
squeaking etc.
 Gear changing can be done while the retarder is engaged.
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37. VOITH Retarder
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38. Technical Specification
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Max. Retarder Torque 1500Nm
Desired deceleration 1 m/s2 (approx.)
Working medium SAE-30, C4 (Mono-grade) Oil
Cooling Medium Same as Engine coolant
Control medium Compressed air
Operating Air Pressure 4.5 Bar
Weight of the Retarder 65 to 85 kgs
Retarder stops below 4 Km/hr
Retarder starts above 10 Km/hr
Vehicle Models
LPO 1616 Diesel
LPO 1618 Diesel

39. Identification
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40. Tightening Torque
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Item No. Designation Dimensions Tightening torque
1500 Screw plug M14X1.5, hexagon socket head, w.a.f. 6 25 Nm
1700 Oil drain plug M24X1.5, hexagon socket head, w.a.f. 12 80 Nm
1900 Non-return valve outlet M48X1.5, hexagon insert bit, w.a.f. 55 280 Nm
2800 Oil filter plug M30X1.5, hexagon socket head, w.a.f. 17 130 Nm
3600 Hex head screw M8X45, hexagon insert bit, w.a.f. 13 Observe tightening sequence
Initial torque: 17 Nm
Final torque: 30 Nm
4703 Screw plug M8X1, hexagon socket head, w.a.f. 5 10 Nm
4800 Hex head screw M8X70 hexagon insert bit, w.a.f. 13 Observe tightening sequence
Initial torque: 17 Nm
Final torque: 30 Nm
5300 Hex head screw M8X20, hexagon insert bit, w.a.f. 13 30 Nm
5400 Hex head nut M8, hexagon insert bit, w.a.f. 13 18 Nm
6200 Hex head screw M10X40, hexagon insert bit, w.a.f. 15 46 Nm
6300 Hex head screw M10X70, hexagon insert bit, w.a.f. 15 46 Nm
7000 Pressure sensor M10X40, hexagon insert bit, w.a.f. 15 30 Nm
8000 Oil temperature sensor M14X1.5, hexagon insert bit, w.a.f. 27 28 Nm
20200 Screw plug M14X1.5, hexagon socket head, w.a.f. 6 25 Nm
20400 Hex head screw M8X45, hexagon insert bit, w.a.f. 13 30 Nm
20600 Coolant temperature sensor M14X1.5, hexagon insert bit, w.a.f. 27 28 Nm

41. Components of Retarder System
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Proportional Valve
Heat Exchanger
Oil Reservoir
Retarder Input Shaft
Rotor
Stator

42. Principle of Operation
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43. Allison Transmission - Retarder
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44. Components & Principle of Operation
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45. Thank You!!!
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