Suspension System

Suspension System

Suspension system is a mechanical device which absorb uneven vehicle shocks. It is a set of mechanical connections, springs, and dampers that connect the wheels to the chassis.

The conventional system, in which the road springs are attached to a rigid beam axle.

The independent system in which there is no rigid axle beam and which is free to move vertically without any reaction on the other wheel.

Need of Suspension System

  1. In order to provide comfortable ride to the passengers and avoid additional stresses in the vehicle frame.
  2. The vehicle should neither bounce or role or sway the passengers when Cornering nor pitch when accelerateing, braking or sudden lifting or dropping of the front wheel with respect to real wheels.
  3. Although some of the road irregularities and inequalities are absorbed by large tyres.
  4. It is necessary to provide a suspension system for reducing the shocks to passengers and for comfortable ride also reduce additional stresses in the automobile frame and body.
  5. All the parts which perform the function of isolating the automobile from the road shock are collectively called as a suspension system.
  6. A good suspension should have springness and damping.
  7. The springness is the elastic resistance to load while damping is ability of absorbing shocks.

Functions of Suspension System

  • To act as a safeguard for the occupants against road shocks and provide comfort ride.
  • To preserve the stability of the vehicle in rolling, pitching while in motion.
  • To minimise the effects of stresses due to road shocks on mechanism of a vehicle and provide cushionong effect.
  • To provide the required height to body structure as well as beer the torque and breaking reaction.
  • To keep the body perfectly in level while travelling over the uneven road.

How Does a Car Suspension Work?

A car suspension system is a crucial component that helps ensure a smooth and controlled ride by managing the impact of road irregularities on the vehicle. The suspension system serves several functions, including providing comfort to passengers, maintaining contact between the tires and the road, and enhancing vehicle stability and handling.


Coil Springs or Leaf Springs: Most cars use coil springs or leaf springs as the primary means of supporting the vehicle’s weight. These springs compress and expand to absorb shocks and bumps from the road.

Shock Absorbers (Dampers):

Purpose: Shock absorbers, commonly referred to as dampers, work in conjunction with springs to control the oscillations created by uneven road surfaces. They ensure that the wheels do not bounce excessively.
Function: When the springs compress and release, shock absorbers dampen the oscillations by converting the kinetic energy into heat. This helps maintain tire contact with the road and prevents excessive bouncing.

Suspension Linkages:

Control Arms: Many vehicles have control arms that connect the chassis to the wheel assembly. These arms, along with other linkages, control the motion of the wheels and help maintain proper alignment.
Bushings: Suspension components often use bushings, which are rubber or polyurethane mounts, to reduce vibrations and noise while allowing for some flexibility.

Anti-roll Bars (Sway Bars):

Purpose: Anti-roll bars are used to reduce body roll during cornering. They connect the left and right sides of the suspension, transferring force from one side to the other to resist the vehicle’s tendency to tilt excessively.
Function: When a car corners, the weight shifts to one side. The anti-roll bar helps distribute the force more evenly between the left and right wheels, improving stability and handling.


Purpose: In some vehicles, struts combine the functions of a spring and a shock absorber in a single unit. Struts are typically used in the front suspension, while shocks and separate springs are used in the rear.
Function: Struts support the weight of the vehicle, control its movement, and provide damping to enhance ride comfort.

Main Parts of Car Suspension System

The suspension system of a car is crucial for providing a smooth ride, handling, and stability. Several components work together to achieve these goals.
Some main car suspension parts:


Coil Springs: These are spiral-wound springs that compress and expand to absorb shocks and bumps.
Leaf Springs: Commonly used in rear suspension systems, these consist of multiple layers of metal strips bound together.

Shock Absorbers (Dampers):

These are hydraulic or gas-filled devices that control the rebound and compression of the springs, preventing the vehicle from bouncing excessively.


A strut is a structural part of the suspension system that combines the coil spring and shock absorber into a single unit. Struts are often used in the front suspension.

Control Arms:

Control arms (also known as A-arms) connect the suspension system to the frame of the vehicle. They help control the wheel’s motion and maintain proper alignment.


Bushings are made of rubber or other materials and are used to isolate and reduce vibrations between moving parts, such as control arms and suspension components.

Sway Bars (Stabilizer Bars):

Sway bars connect the left and right wheels of a car. They help control body roll during cornering, improving stability.

Ball Joints:

Ball joints connect the control arms to the steering knuckles and allow for movement in multiple directions. They are essential for steering and suspension flexibility.

Tie Rods and Tie Rod Ends:

These components connect the steering system to the wheels and are crucial for steering control. Tie rod ends connect the tie rods to the steering knuckles.

Wheel Bearings:

Wheel bearings allow the wheels to rotate smoothly and support the weight of the vehicle.

Strut Mounts:

Strut mounts connect the strut to the vehicle’s body and provide a pivot point for the strut to move.

Alignment Components:

Components such as camber and toe adjustments are important for wheel alignment, ensuring even tire wear and proper handling.

These components work together to provide a balance between ride comfort, handling, and stability. Regular maintenance and inspections are important to ensure the proper functioning of these suspension parts and to address any issues promptly.

Leaf Springs

Leaf springs are a type of suspension system commonly used in vehicles to absorb and distribute the impact of road irregularities and shocks. They consist of multiple layers or “leaves” of spring steel that are stacked on top of each other and secured at the ends. The leaves are progressively longer and are clamped together with a center bolt, creating a flexible and resilient structure.

Construction and Working of Leaf Spring

Leaf Spring
  • Semi-elliptical leaf spring are widely used for suspension in light and heavy commercial vehicle.
  • In car these are used for rear suspension.
  • The leaf springs are made of flat semi-elliptical plate.
  • The advantages of leaf spring over helical spring is that the ends of the spring maybe guided, along the definite path as it deflect to acts as a structural member in addition to energy absorbing device.
  • Thus leaf spring carry lateral load, brake torque, driving thrust and shocks.
  • It consist of number of semi-elliptical plates called blade or leaves.
  • The leaves are given initially curvature or camber so that they tends to straighten under the load.
  • The blades are vary in length and are held together by a bolt passing through the centre acting as a beam of uniform strength.
  • The spring is clamped to the axle housing by means of U bolts.

What is Suspension System In Car : Working, Parts, Type, Material

  • The longest leave is called as master leaves has its end formed in the shaped of an eye through which the boltsare passed tosecure the spring to its supports.
  • The eyes are attached to shackle provided with anti-friction material such as bronze or rubber. The Other leaves are graduated leaves.
  • To prevent digging in the adjacent leaves, the end of graduated leaves are trimmed in various forms.
  • The master leaf has to withstand vertical bending load, side thrust and twisting movement due to presence of stresses caused by these load so it is usually to provide two full length leaves and rest graduated leaves.
  • Reborn clips are located at intermediate position in the length of the spring so that graduated leaves also shear the stresses induced in the full length leaves when the spring rebound.
  • Highly cambered spring provide a soft suspension but they also increase tendency to jaw. Flat spring reduces tendency of the vehicle to dip (pitching), when break or accelerate suddenly.
  • Use of longer is spring give soft suspension.
  • Generally rear spring are kept longer than the front spring. this causes them to vibrate at different frequencies, which prevent excessive bounce.

Forces and Moments acting on Leaf Spring

Leaf springs are a type of suspension system commonly used in vehicles, particularly in the rear suspension of trucks and some older model cars. They consist of multiple layers of flexible metal strips bound together to form a curved or elliptical shape.
The forces and moments acting on a leaf spring can be understood by considering various aspects of its design and function:

Axial Load or Vertical Force (Fz):

The primary purpose of a leaf spring is to support the vehicle’s weight and absorb vertical forces. The axial load is the vertical force acting on the spring due to the weight of the vehicle and its cargo. This force is supported by the flexing of the individual leaves in the spring.

Bending Moment (M):

Bending moments result from the curvature of the leaf spring. When the vehicle encounters bumps or irregularities in the road, the leaf spring flexes and creates a bending moment. The bending moment is the force applied perpendicular to the axis of the spring.

Shear Force (Fy):

Shear forces act parallel to the plane of the leaves. As the spring flexes, the leaves slide past each other, resulting in shear forces. These forces are crucial for distributing the load along the length of the spring.

Torsional Moment (T):

Torsional moments may occur if the spring is subjected to twisting forces. This can happen during cornering or when one wheel encounters a bump while the other remains on a smooth surface. The leaf spring must resist torsional forces to maintain stability.

Lateral Load (Fx):

In addition to vertical loads, leaf springs may experience lateral loads during cornering or when the vehicle is subjected to side forces. The spring should provide some resistance to lateral movement to help maintain proper alignment.

Damping Forces:

Depending on the design, leaf springs may have some inherent damping characteristics. Damping helps control the oscillations of the spring, especially after encountering bumps or other disturbances on the road.

Material Used for Leaf Springs

Leaf springs are commonly used in automotive and other heavy-duty applications to provide suspension and support for vehicles. The materials used for leaf springs have evolved over time, with various alloys and composites being employed to enhance strength, durability, and flexibility.
The most common materials for leaf springs include:

High Carbon Spring Steel:

5160H, 9260, and 51CrV4 are some of the high carbon spring steels commonly used for leaf springs. These steels are known for their high yield strength and excellent resilience, making them suitable for withstanding the repeated flexing and loading that leaf springs experience.

Alloy Steels:

Alloy steels, which contain additional alloying elements such as chromium, silicon, and manganese, are often used to improve specific properties like hardenability and toughness. Alloys like 6150 and 9254 are examples of alloy steels used in leaf spring manufacturing.

Composite Materials:

In some modern applications, composite materials are used to make leaf springs. These composites can include a combination of materials like fiberglass and epoxy. Composite leaf springs offer advantages such as reduced weight and improved corrosion resistance compared to traditional metal leaf springs.

Forged Steel:

Leaf springs are often manufactured using a forging process, where the steel is heated and shaped into the desired form. Forged steel leaf springs tend to have enhanced strength and toughness.

Multi-material Combinations:

Some leaf springs may incorporate multiple materials, such as a combination of steel and rubber. This hybrid approach can provide a balance of strength and damping characteristics.

What is Suspension System In Car : Working, Parts, Type, Material

Type of Suspension System

Rigid Axle suspension

  • Greater part of the extra weight of passengers are and luggage has to be carried by rear suspension in most of the vehicles.
  • In one rigid unit known as a live action, the driving axle combines the right angle drive, differential, axle shaft, and wheel hub mounting. it is connected to the propeller shaft.
  • The unit connected to propeller shaft is attached to the vehicle structure in such a way that it can move up and down on its spring and can cope with the loads as well as the torque or turning forces imposed on it.
  • Further rear suspension is designed in such a way as to position the axle for minimising bouncing and associated vibrations to which is liable while moving off, braking and concerning particularly.
  • For suppressing the bouncing of the springs the damper which are mostly hydraulic and telescopic type are widely used.

The real axle suspensions are

1. Helical coil spring

Helical coil spring
  • It is circular for best energy storing shape for a given weight, and a coil spring store energy produced by its up and down movement in the most efficient way.
  • The energy stored per unit volume is double than leaf Spring.
  • Coil spring has an advantages of fitted in compact space.
  • It takes the shear as well as bending stress only and for the torque reaction and side thrust an alternative arrangement has to be provided.
  • The life of coil is increased by shot paining their surfaces to induce compressive stress in them and to reduce the effect of scratches in initiating fatigue cracks.
  • Immediately after shot such spring maybe given an anticorrosion treatment again to increase their fatigue life.
  • The ends of the coil spring maybe square and ground for stability, upon the surfaces through which the load is applied to the rest of the spring.
  • The tendency of buckling of a spring under compressive load is prevented by mounting it in the cylindrical dampers or shock absorber so that the possibility of buckling is reduced.
  • These spring do not have noise problem and static function.
  • These springs are mainly with independent suspension through they have also been used in the conversional rigid axle suspension.
  • A helper coil spring are provided for progressive stiffness against increase load.

2. Torsion bar

  • The tosson bar is used with independent front suspension system.
  • Two such units are there on either side of the frame.
  • Each suspension housing is pivoted at its front end to the tubular cross member (front axe) and carries at its rear and a wheel carrier arm mounted on needle roller bearings.
  • Wheel hub and brake anchor plate are mounted on the forward end of the wheel carrier arm.
  • Combined torsion bar and torsion tube splined together at their inner and provide main spring load.
  • It is made of heat treated alloy spring steel.
  • One end of the torsion bar is connected by splines with the wheel carrier arm.
  • While the other end of torsional bar asssembly is rigidly connected to the steering knuckle.
  • When the wheel moves, the rod and tube are twisted and the formed and elastic line between the wheel and steering knuckle.
  • The length of the combine torsion bar is composed of the length of the tube and the rod to make softer suspension.
  • Double acting shock absorber assembly is bolted to the rear face of the suspension unit.
  • It is lighter than leaf spring and occupies less space.
  • It does not take braking or driving thrust. So additional linkage must be provided.

Air suspension system

  • Now a days pneumatic suspension system are employed in some tourist vehicles to improve the riding comfort of the passengers.
  • A line diagram of air suspension system with air shown in figure. It consist of four air bags.
  • The elastic element consists of housing, diaphragm with suitable air inlate and piston group. The housing is linked with the frame. The housing contains the piston group which is linked with unsprung mass.
  • The housing and piston group are connected by a metallic diaphragm for better sealing and to friction between the members of elastic elements.
  • Each air bag is filled with compressed air.
  • The component of air suspension system are air filter, compressor, air reservoir, relief valve, pressure regulator, solenoid valve, levelling valve and T check valve.
  • A air compressor is mounted on the vehicle frame supplies high pressure air into the reservoir. The compressor suck the air from atmosphere through air filter.

What is Suspension System In Car : Working, Parts, Type, Material

  • The pressure in the reservoir is maintained at about 20 kg/cm2.
  • The compressed air in the air bags support the weight of vehicle whenever vehicle come across the bump of the surface, the air in the air bag compressed and absorb the shocks.
  • Air is admitted into the four air bag through two circuits. In one circuit a pressure reduced to 12 kg/cm2 by pressure regulator.
  • This pressure is kept in air bag through levelling valve if the pressure in one of the bag is low, the leveling arm moves and air is admitted into low pressure air bag through inlet valve.
  • This can be achieved by special regulator, which keeps the same distance between wheel and frame under the various load. This circuit maintain the vehicle level constant in loaded or unloaded condition.
  • For this situation, the air at 20 kgf/cm2 pressure is admitted into the levelling valve through solenoid valve.
  • Also the air is quickly released by levelling valve whenever load is decreases from corresponding air bag. This lower the air bag and hence the vehicle to the proper level.

What is Suspension System In Car : Working, Parts, Type, Material


What is Suspension system?
Suspension is the system of tires, tire air, springs, shock absorbers, and linkages that connects a vehicle to its wheels and allows relative movement between the two. Suspension systems must support both road grip/handling and ride quality, which are at odds with each other.
A suspension system is a set of mechanical links, springs, and shock absorbers that connect the wheels to the chassis.

What are the 4 types of suspension system?
1. leaf springs
2. Coil springs
3. Torsion bars
4. Air springs

What causes suspension damage?
Major suspension system components include springs, shock absorbers, struts, control arms, and more. Being exposed on the underside of your vehicle, these parts are constantly exposed to debris, rocks, speed bumps, potholes, and other driving incidents that can damage components.

What are the main parts of the suspension?
Main Parts of Suspension System is
1. Spring
2. Wheel
3. Shock absorbers
4. rods
5. Joints, Bearings and Bushings
6. Direction system
7. Frame.

What is the main function of a car suspension?
The primary function of a car’s suspension is to provide a smooth ride and ensure that all wheels remain in contact with the road surface for maximum grip and stability.

How often should a car suspension be replaced?
Modern car suspension systems usually last between 50,000 and 1 lakh kilometres. However, this depends on the conditions of the road on which the vehicle is driven and the care with which it has been driven on those roads.

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By Aditya

Hi, I’m Aditya Sharma, a professional blogger from Gurgaon, India and I launched this blog called aadityacademy on July 2021. is a mechanical Project-oriented platform run by Aditya sharma and I got the motivation to start aadityacademy blog after seeing less technical education information available on google.

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