---
title: "Suspension system, springs, dampers, stabilizer bar"
subject: "Automotive Technology"
chapter: 6
key: "semester_5/automotive_technology:suspension-springs-and-dampers"
source: https://www.bctengineer.com/q/semester_5/automotive_technology/suspension-springs-and-dampers
site: BCT Engineering
---

# Suspension system, springs, dampers, stabilizer bar

Automotive Technology · Chapter 6: Suspension and Steering

- Asked in: year not given, 8 marks
- Video: [Suspension System Components](https://www.youtube.com/watch?v=AVsBgoU88MU) — Vehicle Engineering
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_5/automotive_technology/suspension-springs-and-dampers
- Whole chapter: https://www.bctengineer.com/md/semester_5/automotive_technology/chapter-6

## Question

State the purposes of a vehicle suspension system. Describe the types of springs used in suspension. Explain the working of a telescopic hydraulic shock absorber and the function of a stabilizer (anti-roll) bar.

## Short answer

Suspension isolates body from shocks, maintains tyre contact, and supports weight. Springs include leaf, coil, torsion bar, air, and rubber types. A telescopic hydraulic damper forces oil through orifices during bump and rebound, dissipating energy. A stabilizer bar connects left and right suspension arms, twisting to reduce body roll in corners.

## Answer

#### Purposes of suspension

- Isolate the body from road shocks for ride comfort.
- Keep the tyres in contact with the road for good traction and braking.
- Support the vehicle weight and carry loads.
- Maintain correct wheel alignment and control body roll, pitch and squat.
- Transmit driving, braking and cornering forces to the frame.

#### Types of springs

| Spring | Description | Use |
|---|---|---|
| Leaf spring | Several steel leaves of unequal length (semi-elliptic); damping by inter-leaf friction | Trucks, buses, rear axles |
| Coil spring | Helically wound steel bar; light, compact; needs links to locate axle | Most cars (MacPherson, wishbone) |
| Torsion bar | Steel bar twisted when the arm moves | Some light trucks and cars |
| Air spring | Rubber bellows with compressed air; stiffness and height adjustable | Buses, luxury cars |
| Rubber / hydro-pneumatic | Rubber block, fluid + gas | Small cars, special cars |

#### Telescopic shock absorber (damper)

A spring stores energy and would keep oscillating, so a damper is fitted in parallel to convert oscillation energy into heat.

```text
   top mount (body)
        |
   [ piston rod ]
   |  +--------+  | <- oil
   |  | piston |  |    valves in piston
   |  +--------+  |
   |   oil + gas  |
   bottom mount (axle)
```

The cylinder is filled with oil. During **bump** the piston moves down and oil is pushed through small orifices and valves into the upper chamber. During **rebound** it flows back through other valves, giving more resistance (higher in rebound than bump, typically 2:1). The restriction of oil flow creates the damping force. A gas-charged (monotube) design avoids foaming.

#### Stabilizer (anti-roll) bar

A U-shaped steel torsion bar connected between the left and right suspension arms. In a corner, the outer wheel moves up and the inner wheel moves down; the bar twists and resists this. It reduces **body roll**, improves handling and keeps both tyres on the road.

## Check yourself

The answer's key points as multiple-choice questions, with the correct option and why.

1. Which is a purpose of suspension?
   A. Increase engine torque
   B. Keep tyres in contact with the road and isolate the body from shocks
   C. Reduce gear ratios
   D. Cool brakes
   Answer: B. It gives comfort, traction and braking contact, carries load and controls roll and pitch. (Key point: Purposes)

2. Which spring uses inter-leaf friction for damping and is common on trucks?
   A. Coil
   B. Torsion bar
   C. Leaf spring
   D. Air spring
   Answer: C. Semi-elliptic leaf springs damp by friction between leaves and suit trucks, buses and rear axles. (Key point: Spring types)

3. How does a telescopic damper provide damping?
   A. Oil forced through small orifices and valves; more resistance in rebound than bump
   B. Stores energy elastically
   C. Gas compresses only
   D. Friction between leaves
   Answer: A. Restricted oil flow converts oscillation energy into heat; rebound resistance is typically about twice that of bump. (Key point: Shock absorber)

4. What does the stabilizer bar do in a corner?
   A. Twists to resist the opposite movement of left and right wheels, reducing body roll
   B. Lifts the body
   C. Increases pitch
   D. Locks the axle
   Answer: A. The U-shaped torsion bar resists outer wheel rising and inner falling, reducing roll and improving handling. (Key point: Anti-roll bar)

## Related in Automotive Technology

- [Anti-lock braking system and EBD](https://www.bctengineer.com/question.md?key=semester_5%2Fautomotive_technology%3Aabs-and-ebd-systems) — Automotive Technology, chapter 7
- [Electric vehicle architecture and traction motors](https://www.bctengineer.com/question.md?key=semester_5%2Fautomotive_technology%3Aev-architecture-and-motors) — Automotive Technology, chapter 12
- [Hydraulic and air brake systems compared](https://www.bctengineer.com/question.md?key=semester_5%2Fautomotive_technology%3Ahydraulic-vs-pneumatic-brakes) — Automotive Technology, chapter 7
- [Charging system and starting system](https://www.bctengineer.com/question.md?key=semester_5%2Fautomotive_technology%3Aalternator-and-starter-motor-systems) — Automotive Technology, chapter 9

## Related in other subjects

- [Undamped dynamic vibration absorber](https://www.bctengineer.com/question.md?key=semester_7%2Ftheory_of_mechanism_and_machine_ii%3Adynamic-vibration-absorber-design) — Theory of Mechanism and Machine II, chapter 7
- [Human-vehicle-environment system; driver characteristics](https://www.bctengineer.com/question.md?key=semester_7%2Ftransportation_engineering_ii%3Ahve-system-driver-physical-characteristics) — Transportation Engineering II, chapter 1
- [Reactor function and ring bus-bar scheme](https://www.bctengineer.com/question.md?key=semester_7%2Fpower_plant_equipment%3Aring-bus-reactor-scheme) — Power Plant Equipment, chapter 4
- [Use and working principle of subtense bar](https://www.bctengineer.com/question.md?key=semester_4%2Fsurveying_ii%3Asubtense-bar-use-working-principle) — Surveying II, chapter 2