Air Suspension
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Air suspension is a type of vehicle
suspension Suspension or suspended may refer to: Science and engineering * Suspension (topology), in mathematics * Suspension (dynamical systems), in mathematics * Suspension of a ring, in mathematics * Suspension (chemistry), small solid particles suspende ...
powered by an electric or engine-driven air pump or compressor. This compressor pumps the air into a flexible
bellows A bellows or pair of bellows is a device constructed to furnish a strong blast of air. The simplest type consists of a flexible bag comprising a pair of rigid boards with handles joined by flexible leather sides enclosing an approximately airtig ...
, usually made from textile-reinforced rubber. Unlike
hydropneumatic suspension Hydropneumatic suspension is a type of motor vehicle suspension system, designed by Paul Magès, invented by Citroën, and fitted to Citroën cars, as well as being used under licence by other car manufacturers, notably Rolls-Royce ( Silver Sha ...
, which offers many similar features, air suspension does not use pressurized liquid, but pressurized air. The air pressure inflates the bellows, and raises the chassis from the axle.


Overview

Air suspension is used in place of conventional steel springs in heavy vehicle applications such as buses and
truck A truck or lorry is a motor vehicle designed to transport cargo, carry specialized payloads, or perform other utilitarian work. Trucks vary greatly in size, power, and configuration, but the vast majority feature body-on-frame constructi ...
s, and in some passenger cars. It is widely used on
semi trailer A semi-trailer is a trailer without a front axle. In the United States, the term is also used to refer to the combination of a truck and a semi-trailer; a tractor-trailer. A large proportion of a semi-trailer's weight is supported by a tracto ...
s and
train In rail transport, a train (from Old French , from Latin , "to pull, to draw") is a series of connected vehicles that run along a railway track and transport people or freight. Trains are typically pulled or pushed by locomotives (often ...
s (primarily
passenger trains In rail transport, a train (from Old French , from Latin , "to pull, to draw") is a series of connected vehicles that run along a railway track and transport people or freight. Trains are typically pulled or pushed by locomotives (often know ...
). The purpose of air suspension is to provide a smooth, constant
ride quality Ride quality refers to a vehicle's effectiveness in insulating the occupants from undulations in the road surface (e.g., bumps or corrugations). A vehicle with good ride quality provides a comfort for the driver and passengers. Importance Good r ...
, but in some cases is used for sports suspension. Modern electronically controlled systems in automobiles and light trucks almost always feature self-leveling along with raising and lowering functions. Although traditionally called air bags or air bellows, the correct term is air spring (although these terms are also used to describe just the rubber bellows element with its end plates).


History

On 7 January 1901 the British engineer Archibald Sharp patented a method for making a seal allowing pneumatic or hydraulic apparatus described as a "rolling mitten seal", and on 11 January 1901 he applied for a patent for the use of the device to provide air suspension on bicycles. Further developments using this 1901 seal followed. A company called Air Springs Ltd started producing the A.S.L. motorcycle in 1909. This was unusual in having pneumatic suspension at front and rear - rear suspension being unusual in any form of motorcycle at that time. The suspension units were similar to the normal girder forks with the spring replaced by a telescopic air unit which could be pressurised to suit the rider. Production of the motorcycles ceased in 1914. On 22 January 1901 an American, William W. Humphreys, patented an idea - a 'Pneumatic Spring for Vehicles'. The design consisted of a left and right air spring longitudinally channeled nearly the length of the vehicle. The channels were concaved to receive two long pneumatic cushions. Each one was closed at one end and provided with an air valve at the other end. From 1920, Frenchman
George Messier George Messier (1896–1933) was a French inventor who is best known as the pioneer of hydraulically-operated landing gear for aircraft. He also specialized in hydropneumatic suspension Hydropneumatic suspension is a type of motor vehicle suspe ...
provided aftermarket pneumatic suspension systems. His own 1922-1930 Messier automobiles featured a suspension "to hold the car aloft on four gas bubbles." During
World War II World War II or the Second World War, often abbreviated as WWII or WW2, was a world war that lasted from 1939 to 1945. It involved the vast majority of the world's countries—including all of the great powers—forming two opposin ...
, the U.S. developed the air suspension for heavy aircraft in order to save weight with compact construction. Air systems were also used in heavy trucks and aircraft to attain
self-levelling suspension Self-levelling refers to an automobile suspension system that maintains a constant ride height of the vehicle above the road, regardless of load. Purpose Many vehicle systems on a conventional vehicle are negatively affected by the change in attit ...
. With adjustable air pressure, the axle height was independent of vehicle load. In 1946, American
William Bushnell Stout William Bushnell Stout (March 16, 1880 – March 20, 1956) was a pioneering American inventor, engineer, developer and designer whose works in the automotive and aviation fields were groundbreaking. Known by the nickname "Bill", Stout designed an ...
built a non-production prototype Stout Scarab that featured numerous innovations, including a four-wheel independent air suspension system. In 1950
Air Lift Company
patented a rubber air spring that is inserted into a car's factory coil spring. The air spring expanded into the spaces in the coil spring, keeping the factory spring from fully compressing, and the vehicle from sagging. The air springs were also commonly used on
NASCAR The National Association for Stock Car Auto Racing, LLC (NASCAR) is an American auto racing sanctioning and operating company that is best known for stock car racing. The privately owned company was founded by Bill France Sr. in 1948, and hi ...
race cars for many years. In 1954, Frenchman
Paul Magès Paul Ernest Mary Magès (1908–1999) is known for his invention of the first self-leveling automobile suspension, known as hydro-pneumatic suspension. This system replaced conventional steel springs with an adaptive system of hydraulic struts, r ...
developed a functioning air/oil
hydropneumatic suspension Hydropneumatic suspension is a type of motor vehicle suspension system, designed by Paul Magès, invented by Citroën, and fitted to Citroën cars, as well as being used under licence by other car manufacturers, notably Rolls-Royce ( Silver Sha ...
, incorporating the advantages of earlier air suspension concepts, but with hydraulic fluid rather than air under pressure. Citroën replaced the conventional steel springs on the rear axle of their top-of-range model, the Traction Avant 15 Hydraulique. In 1955, the
Citroën DS The Citroën DS () is a front mid-engined, front-wheel drive executive car manufactured and marketed by Citroën from 1955 to 1975, in fastback/sedan, wagon/estate, and convertible body configurations, across three series of one generation. ...
incorporated four wheel hydropneumatic suspension. This combined a very soft, comfortable suspension, with controlled movements, for sharp handling, together with a
self-levelling suspension Self-levelling refers to an automobile suspension system that maintains a constant ride height of the vehicle above the road, regardless of load. Purpose Many vehicle systems on a conventional vehicle are negatively affected by the change in attit ...
. In 1956 air suspension was used on EMD's experimental
Aerotrain Aerotrain may refer to: * Aérotrain, a hovercraft train developed in France * AeroTrain, an tiltrotor aircraft proposed by Karem Aircraft * Aerotrain (GM), a passenger train built by General Motors Electro-Motive Division * AeroTrain (Washington ...
. In the U.S., General Motors built on its World War II experience with air suspension for trucks and airplanes. It introduced air suspension as standard equipment on the new 1957 Cadillac Eldorado Brougham. An "Air Dome" assembly at each wheel included sensors to compensate for uneven road surfaces and to automatically maintain the car's height. For 1958 and 1959, the system continued on the Eldorado Brougham, and was offered as an extra cost option on other Cadillacs. In 1958, Buick introduced an optional "Air-Poised Suspension" with four cylinders of air (instead of conventional coil springs) for automatic leveling, as well as a "Bootstrap" control on the dashboard to raise the car for use on steep ramps or rutted country roads, as well as for facilitating tire changes or to clean the
whitewall tire Whitewall tires or white sidewall (WSW) tires are tires having a stripe or entire sidewall of white rubber. These tires were most commonly used from the early 1900s to around the mid 1980s. Background The use of whitewall rubber for tire has be ...
s. For 1959, Buick offered an optional "Air Ride" system on all models that combined "soft-rate" steel coil springs in the front with air springs in the rear. An optional air suspension system was available on the 1958 and 1959 Rambler Ambassadors, as well as on all
American Motors American Motors Corporation (AMC; commonly referred to as American Motors) was an American automobile manufacturing company formed by the merger of Nash-Kelvinator Corporation and Hudson Motor Car Company on May 1, 1954. At the time, it was the ...
"Cross Country" station wagon models. The "Air-Coil Ride" utilized an engine-driven compressor, reservoir, air bags within the coil springs, and a ride-height control, but the $99 optional system was not popular among buyers and American Motors (AMC) discontinued it for 1960. Only Cadillac continued to offer air suspension through the 1960 model year, where it was standard equipment on the Eldorado Seville, Biarritz, and Brougham. In 1960, the Borgward P 100 was the first German car with self-levelling air suspension. In 1962, the
Mercedes-Benz W112 : ''See Mercedes-Benz S-Class for a complete overview of all S-Class models.'' The Mercedes-Benz W112 is a luxury automobile produced by Mercedes-Benz from 1961 to 1967. Marketed as the 300SE, it was available as a coupé, convertible, sedan, ...
platform featured an air suspension on the 300SE models. The system used a Bosch main valve with two axle valves on the front and one on the rear. These controlled a cone-shaped air spring on each wheel axle. The system maintained a constant ride height utilizing an air reservoir that was filled by a single-cylinder air compressor powered by the engine. In 1964, the
Mercedes-Benz 600 The Mercedes-Benz 600 (W100) is a line of ultra-luxury cars produced by Daimler-Benz from 1963 to 1981. The forerunner of the modern Maybach marque, the ''Grosser Mercedes'' ("Grand Mercedes") succeeded the Type 300d "Adenauer" as the compa ...
used larger air springs and the compressed air system also powered the brake servo.
Rolls-Royce Rolls-Royce (always hyphenated) may refer to: * Rolls-Royce Limited, a British manufacturer of cars and later aero engines, founded in 1906, now defunct Automobiles * Rolls-Royce Motor Cars, the current car manufacturing company incorporated in ...
incorporated
self-levelling suspension Self-levelling refers to an automobile suspension system that maintains a constant ride height of the vehicle above the road, regardless of load. Purpose Many vehicle systems on a conventional vehicle are negatively affected by the change in attit ...
on the 1965
Rolls-Royce Silver Shadow The Rolls-Royce Silver Shadow is a full-sized luxury car produced by British automaker Rolls-Royce in various forms from 1965 to 1980. It was the first of the marque to use unitary body and chassis construction. The Silver Shadow was produced ...
, a system built under license from Citroën. In 1975, the
Mercedes-Benz 450SEL 6.9 The 450 SEL 6.9 is the high-performance version of the W116 S-Class saloon. It was based on the long-wheelbase version of W116 chassis introduced in 1972 and equipped with Mercedes-Benz M100 V8 engine and full hydropneumatic suspension system. T ...
incorporated a
hydropneumatic suspension Hydropneumatic suspension is a type of motor vehicle suspension system, designed by Paul Magès, invented by Citroën, and fitted to Citroën cars, as well as being used under licence by other car manufacturers, notably Rolls-Royce ( Silver Sha ...
when the patents on the technology had expired. This design replaced the expensive, complex, and problematic compressed air system that was still used on the 600 models until 1984. Air suspension was not included in standard production American-built cars between 1960 and 1983. In 1984,
Ford Motor Company Ford Motor Company (commonly known as Ford) is an American multinational automobile manufacturer headquartered in Dearborn, Michigan, United States. It was founded by Henry Ford and incorporated on June 16, 1903. The company sells automobi ...
incorporated a new design as a feature on the
Lincoln Continental Mark VII The Continental Mark VII, later changed to Lincoln Mark VII, is a rear wheel drive luxury coupe that was produced by Lincoln. Introduced in August 1983 for the 1984 model year, the Continental Mark VII shared its Ford Fox platform with the Ford ...
. In 1986,
Toyota Soarer The is a Personal luxury car, personal luxury Grand tourer, GT coupé produced from 1981 to 2005 by Toyota and sold in Japan. It was available at both Japanese Toyota dealerships called ''Toyota Store'' and ''Toyopet Store'', and it debuted with ...
introduced the first electronically controlled (
TEMS Temilade Openiyi (born 11 June 1995), known professionally as Tems, is a Nigerian singer. She rose to prominence after she was featured on Wizkid's 2020 single "Essence," which reached the top ten of the ''Billboard'' Hot 100 after the releas ...
), a semi-active full air suspension (spring constant, variable attenuation force). Dunlop Systems Coventry UK were also pioneers of Electronically Controlled Air Suspension (ECAS) for off-road vehicles - the term ECAS was successfully trade marked. The system was first fitted to the 93MY Land Rover Range Rover. In 1989
Arnott Air Suspension Products
is founded, eventually expanding to a 300,000 square foot manufacturing plant in Merritt Island, Fl., including 65,000 sq. ft Research & Development center dedicated to Air Suspension, assisting in patents for BMW, Mercedes-Benz and more. In 2002 the GMT 360 Trail Blazer SUV featured rear air assist air suspension with Dunlop air springs and an integrated Wabco control system. In 2005 the GM H2 HUMMER featured an optional rear air suspension system with a dual compressor control system from Dunlop to support tire inflation for off-road applications. In 2013, the
Tesla Model S The Tesla Model S is a battery-powered liftback car serving as the flagship model of Tesla, Inc. The Model S features a dual-motor, all-wheel drive layout, although earlier versions of the Model S featured a rear-motor and rear-wheel drive ...
began offering height adjustable air suspension.


Modern automobiles

Vehicles that have used air suspension include models from
Maybach Maybach (, ) is a German luxury car brand that exists today as a part of Mercedes-Benz. The original company was founded in 1909 by Wilhelm Maybach and his son Karl Maybach, originally as a subsidiary of ''Luftschiffbau Zeppelin GmbH'', and ...
,
Rolls-Royce Rolls-Royce (always hyphenated) may refer to: * Rolls-Royce Limited, a British manufacturer of cars and later aero engines, founded in 1906, now defunct Automobiles * Rolls-Royce Motor Cars, the current car manufacturing company incorporated in ...
,
Lexus is the luxury vehicle division of the Japanese automaker Toyota. The Lexus brand is marketed in more than 90 countries and territories worldwide and is Japan's largest-selling make of premium cars. It has ranked among the 10 largest Japanese ...
, Jeep,
Ram Ram, ram, or RAM may refer to: Animals * A male sheep * Ram cichlid, a freshwater tropical fish People * Ram (given name) * Ram (surname) * Ram (director) (Ramsubramaniam), an Indian Tamil film director * RAM (musician) (born 1974), Dutch * ...
, Cadillac (GM),
Mercedes-Benz Mercedes-Benz (), commonly referred to as Mercedes and sometimes as Benz, is a German luxury and commercial vehicle automotive brand established in 1926. Mercedes-Benz AG (a Mercedes-Benz Group subsidiary established in 2019) is headquartere ...
, Citroën, Porsche,
Land Rover Land Rover is a British brand of predominantly four-wheel drive, off-road capable vehicles, owned by multinational car manufacturer Jaguar Land Rover (JLR), since 2008 a subsidiary of India's Tata Motors. JLR currently builds Land Rovers ...
, SsangYong,
Audi Audi AG () is a German automotive manufacturer of luxury vehicles headquartered in Ingolstadt, Bavaria, Germany. As a subsidiary of its parent company, the Volkswagen Group, Audi produces vehicles in nine production facilities worldwide. Th ...
, Subaru,
Volkswagen Volkswagen (),English: , . abbreviated as VW (), is a German motor vehicle manufacturer headquartered in Wolfsburg, Lower Saxony, Germany. Founded in 1937 by the German Labour Front under the Nazi Party and revived into a global brand post-W ...
,
Lincoln Lincoln most commonly refers to: * Abraham Lincoln (1809–1865), the sixteenth president of the United States * Lincoln, England, cathedral city and county town of Lincolnshire, England * Lincoln, Nebraska, the capital of Nebraska, U.S. * Lincol ...
,
Ford Ford commonly refers to: * Ford Motor Company, an automobile manufacturer founded by Henry Ford * Ford (crossing), a shallow crossing on a river Ford may also refer to: Ford Motor Company * Henry Ford, founder of the Ford Motor Company * Ford F ...
, and Tesla, among others. Some Citroën vehicles feature
Hydractive Hydropneumatic suspension is a type of motor vehicle suspension system, designed by Paul Magès, invented by Citroën, and fitted to Citroën cars, as well as being used under licence by other car manufacturers, notably Rolls-Royce ( Silver Sha ...
suspension, a computer controlled version of their Hydropneumatic system, which features sport and comfort modes, lowers the height of the car at high speeds and continues to maintain ride height when the engine is not running. The air suspension designs from Lincoln, Land Rover, SsangYong, Chrysler, Subaru, Audi, Volkswagen, Tesla, Porsche, and Lexus models feature
height adjustable suspension Height adjustable suspension is a feature of certain automobile suspension systems that allow the motorist to vary the ride height or ground clearance. This can be done for various reasons including giving better ground clearance over rough terrain ...
suitable for making it easier to enter the vehicle, clear bumps, or clear rough terrain. The Lincoln Continental, Town Car, Navigator and Mark VIII also featured an air suspension system which offered a controlled but smooth ride. Jaguar and Porsche has taken this to the next level on their XJ and Panamera models, with a system that changes the spring rate and damping settings, among other changes, for their sport/track modes. The Mark VIII suspension settings were also linked to the memory seat system, meaning that the car would automatically adjust the suspension to individual drivers. The control system in the Mark VIII can lower the suspension by about 25 mm (1 inch) at speeds exceeding about 100 km/h (60 mph) for improved
aerodynamic Aerodynamics, from grc, ἀήρ ''aero'' (air) + grc, δυναμική (dynamics), is the study of the motion of air, particularly when affected by a solid object, such as an airplane wing. It involves topics covered in the field of fluid dyn ...
performance. One way automakers strive to improve gas mileage is by utilizing active suspension technology.
Tesla Motors Tesla, Inc. ( or ) is an American multinational automotive and clean energy company headquartered in Austin, Texas. Tesla designs and manufactures electric vehicles (electric cars and trucks), battery energy storage from home to grid- ...
offers an included "Active Air Suspension" on the
Model S The Tesla Model S is a battery-powered liftback car serving as the flagship model of Tesla, Inc. The Model S features a dual-motor, all-wheel drive layout, although earlier versions of the Model S featured a rear-motor and rear-wheel drive l ...
and Model X to lower or raise the vehicle for aerodynamics and increased range. In 2014 the new C217 S-Class Coupe introduced an update to Magic Body Control, called Active Curve Tilting. This new system allows the vehicle to lean up to 2.5 degrees into a turn, similar to a
tilting train A tilting train is a train that has a mechanism enabling increased speed on regular rail tracks. As a train (or other vehicle) rounds a curve at speed, objects inside the train experience centrifugal force. This can cause packages to slide ab ...
. The leaning is intended to counter the effect of
centrifugal force In Newtonian mechanics, the centrifugal force is an inertial force (also called a "fictitious" or "pseudo" force) that appears to act on all objects when viewed in a rotating frame of reference. It is directed away from an axis which is parall ...
on the occupants and is available only on rear-wheel drive models.


Custom applications

Over the last decade or so air suspension has become popular in the custom automobile culture: street rods, trucks, cars, and even motorcycles may have air springs. They are used in these applications to provide an adjustable suspension which allows vehicles to sit extremely low, yet be able rise to a level high enough to maneuver over obstacles and inconsistencies on paved surfaces. These systems generally employ small, electric or engine-driven
air compressor An air compressor is a pneumatic device that converts power (using an electric motor, diesel or gasoline engine, etc.) into potential energy stored in pressurized air (i.e., compressed air). By one of several methods, an air compressor forces m ...
s which sometimes fill an on-board air receiver tank which stores compressed air for use in the future without delay. It is important that the tank is sized for the task and can be calculated using a specific formula involving the compressor output, standard atmospheric pressure and compressed pressure. High-pressured industrial gas bottles (such as
nitrogen Nitrogen is the chemical element with the symbol N and atomic number 7. Nitrogen is a nonmetal and the lightest member of group 15 of the periodic table, often called the pnictogens. It is a common element in the universe, estimated at se ...
or
carbon dioxide Carbon dioxide ( chemical formula ) is a chemical compound made up of molecules that each have one carbon atom covalently double bonded to two oxygen atoms. It is found in the gas state at room temperature. In the air, carbon dioxide is trans ...
tanks used to store
shielding gas Shielding gases are inert or semi-inert gases that are commonly used in several welding processes, most notably gas metal arc welding and gas tungsten arc welding (GMAW and GTAW, more popularly known as MIG (Metal Inert Gas) and TIG (Tungsten Iner ...
es for welding) are sometimes used in more radical air suspension setups. Either of these reservoir systems may be fully adjustable, being able to adjust each wheel's air pressure individually. This allows the user to tilt the vehicle side-to-side, front-to-back, in some instances "hit a 3-wheel" (contort the vehicle so one wheel lifts up from the ground) or even "hop" the entire vehicle into the air. When a pressure reservoir is present, the flow of air or gas is commonly controlled with pneumatic
solenoid valve A solenoid valve is an electromechanically operated valve. Solenoid valves differ in the characteristics of the electric current they use, the strength of the magnetic field they generate, the mechanism they use to regulate the fluid, and the ty ...
s. This allows the user to make adjustments by simply pressing a momentary-contact electric button or switch. The installation and configuration of these systems varies for different makes and models but the underlying principle remains the same. The metal spring (coil or leaf) is removed, and an air bag, also referred to as an air spring, is inserted or fabricated to fit in the place of the factory spring. When air pressure is supplied to the air bag, the suspension can be adjusted either up or down (lifted or lowered). For vehicles with
leaf spring suspension A leaf spring is a simple form of spring (device), spring commonly used for the suspension (vehicle), suspension in wheeled vehicles. Originally called a ''laminated'' or ''carriage spring'', and sometimes referred to as a semi-elliptical spring, ...
such as pickup trucks, the leaf spring is sometimes eliminated and replaced with a multiple-bar linkage. These bars are typically in a
trailing arm A (semi) trailing-arm suspension, sometimes referred to as (semi) trailing-link is a vehicle axle or wheel suspension design in which one or more horizontal arms (or "links"), perpendicular to and forward of the axle, are connecting the axle or ...
configuration and the air spring may be situated vertically between a link bar or the axle housing and a point on the vehicle's frame. In other cases, the air bag is situated on the opposite side of the axle from the main link bars on an additional cantilever member. If the main linkage bars are oriented parallel to the longitudinal (driving) axis of the car, the axle housing may be constrained laterally with either a
Panhard rod A Panhard rod (also called Panhard bar, track bar, or track rod) is a suspension link that provides lateral location of the axle. Originally invented by the Panhard automobile company of France in the early twentieth century, this device has been ...
or
Watt's linkage In kinematics, Watt's linkage (also known as the parallel linkage) is a type of mechanical linkage invented by James Watt in which the central moving point of the linkage is constrained to travel on a nearly straight line. It was described i ...
. In some cases, two of the link bars may be combined into a triangular shape which effectively constrains the vehicles axle laterally. Often, owners may desire to lower their vehicle to such an extent that they must cut away portions of the frame for more clearance. A reinforcement member commonly referred to as a C-notch is then bolted or welded to the vehicle frame in order to maintain structural integrity. Specifically on pickup trucks, this process is termed "notching" because a portion (notch) of the cargo bed may also be removed, along with the wheel wells, to provide maximum axle clearance. For some, it is desirable to have the vehicle so low that the frame rests on the ground when the air bags are fully deflated. Owners generally choose between having their cars 'tuck' their wheels into the arches when their air suspension is fully lowered or alternatively they can choose to go for 'fitment' which in partnership with stretched tyres sees the arch itself fit in between the tyre and rim. Air suspension is also a common suspension upgrade for those who tow or haul heavy loads with their pick-up truck, SUV, van or car. Air springs, also called "air helper springs," are placed on existing suspension components on the rear or front of the vehicle in order to increase the load capacity. One of the advantages of using air suspension as a load support enhancement is the air springs can be deflated when not towing or hauling and therefore maintaining the factory ride quality.


Electronic Air Suspension

Electronic Controlled Air Suspension (ECAS) is the name of the air suspension system installed on the
Range Rover Classic The Range Rover Classic is a 4x4, mid-size Sport utility vehicle series produced from 1969 to 1996 – initially by the Rover (later Land Rover) division of British Leyland, and latterly by the Rover Group. The first generation of vehicles pro ...
in 1993 and later on the Range Rover P38A. It was developed in the early 1990s by the company now known as Dunlop Systems and Components Ltd in Coventry, UK. ECAS provides variable-height suspension for on- and off-road applications. The five suspension heights typically offered by ECAS are (from lowest to highest in terms of height) "Loading," "Highway," "Standard," "Off-Road," and "Off-Road Extended." Height is controlled automatically based on speed and undercarriage sensors, but a manual ride height switch allows control over the suspension by the driver. The "Loading" and "Off-Road" heights are available only at speeds typically less than . The "Highway" setting is not available manually; it is set when the vehicle moves at over typically for over 30 seconds. Unlike a mechanical spring system (where deflection is proportional to load), height may be varied independently from the load by altering the pressure in the air springs. The air springs were designed to provide a smooth ride, with the additional ability to raise the body of the vehicle for off-road clearance and lower it for higher-speeds road driving. Mechanical springs, for which deflection is proportional to load, cannot do this; with ECAS height is largely independent of load. The developers of ECAS also designed LoadSafe, a related system to ascertain load and change in load on an LCV type vehicle fitted with air springs.


Components

The system comprises: * a vulcanised rubber air spring at each wheel * an
air compressor An air compressor is a pneumatic device that converts power (using an electric motor, diesel or gasoline engine, etc.) into potential energy stored in pressurized air (i.e., compressed air). By one of several methods, an air compressor forces m ...
, which is typically located in the trunk (boot) or under the
bonnet A Bonnet is a variety of headgear, hat or cap Specific types of headgear referred to as "bonnets" may include Scottish * Blue bonnet, a distinctive woollen cap worn by men in Scotland from the 15th-18th centuries And its derivations: ** Fea ...
* a compressed air storage tank may be included for rapid "kneel", storing air at ~150psi (1000 kPa), note (1psi=6.89kPa) * a valve block which routes air from the storage tank to the four air springs via a series of
solenoids upright=1.20, An illustration of a solenoid upright=1.20, Magnetic field created by a seven-loop solenoid (cross-sectional view) described using field lines A solenoid () is a type of electromagnet formed by a helix, helical coil of wire whose ...
,
valves A valve is a device or natural object that regulates, directs or controls the flow of a fluid (gases, liquids, fluidized solids, or slurries) by opening, closing, or partially obstructing various passageways. Valves are technically fitting ...
and many
o-rings An O-ring, also known as a packing or a toric joint, is a mechanical gasket in the shape of a torus; it is a loop of elastomer with a round cross-section, designed to be seated in a groove and compressed during assembly between two or more part ...
* an ECAS computer which communicates with the car's main computer the BeCM and decides where to route air pressure * a series of 6 mm air pipes which channel air throughout the system (mainly from the storage tank to the air springs via the valve block) * an air drier canister containing desiccant * height sensors ideally on all 4 vehicle corners based, typically, on resistive contact sensing to give an absolute height reference for each corner of the vehicle. * Dunlop Systems and Components Ltd have continued to develop the products to the point where the Electronic Control Unit (ECU) is now able to fit under the vehicle floor. The control valves are much smaller and lighter and they produce their own range of compressors.


Multi-Chamber air suspension

The Multi-Chamber air suspension is a suspension capable of controlling the spring characteristics of the air suspension step by step.


Application


=

Genesis G90 The Genesis G90 is a full-size luxury sedan manufactured by the Korean automaker Genesis, which is the luxury vehicle division of Hyundai Motor Company, since 2015. The G90 is the successor of the Hyundai Equus and was known as the Genesis EQ900 ...

= Multi-Chamber air suspension applicated on the Genesis G90 consists of three chambers. Three chambers are used for a smooth ride, and one chamber is used for a dynamic driving feeling. A solenoid valve located between each chamber and a separate electronic control unit oversees the control process. In addition, the basic minimum ground height of 148mm is divided into four stages: high, normal, low, and ultra-low according to the driving mode, driving speed, and driving environment. depending on the driving mode, driving speed, and driving environment. And it informs the driver of the garage control through the infotainment screen. The speed bump control, the hump control, the slope control, and the high-speed driving control functions are activated under the air suspension control.


Common air suspension problems

Air bag or air strut failure is usually caused by wet rust, due to old age, or moisture within the air system that damages it from the inside. Air ride suspension parts may fail because rubber dries out. Punctures to the air bag may be caused from debris on the road. With custom applications, improper installation may cause the air bags to rub against the vehicle's frame or other surrounding parts, damaging it. The over-extension of an air spring which is not sufficiently constrained by other suspension components, such as a shock absorber, may also lead to the premature failure of an air spring through the tearing of the flexible layers. Failure of an air spring may also result in complete immobilization of the vehicle, since the vehicle will rub against the ground or be too high to move. However, most modern automotive systems have overcome many of these problems. Air line failure is a failure of the tubing which connects the air bags or struts to the rest of the air system, and is typically DOT-approved nylon air brake line. This usually occurs when the air lines, which must be routed to the air bags through the chassis of the vehicle, rub against a sharp edge of a chassis member or a moving suspension component, causing a hole to form. This mode of failure will typically take some time to occur after the initial installation of the system, as the integrity of a section of air line is compromised to the point of failure due to the rubbing and resultant abrasion of the material. An air line failure may also occur if a piece of road debris hits an air line and punctures or tears it, although this is unlikely to occur in normal road use. It does occur in harsh off-road conditions but it still not common if correctly installed. Air fitting failure usually occurs when they are first fitted or very rarely in use. Cheap low quality components tend to be very unreliable. Air fittings are used to connect components such as bags, valves, and solenoids to the air line that transfers the air. They are screwed into the component and for the most part push-in or push-to-fit DOT line is then inserted into the fitting. Compressor failure is primarily due to leaking air springs or air struts. The compressor will burn out trying to maintain the correct air pressure in a leaking air system. Compressor burnout may also be caused by moisture from within the air system coming into contact with its electronic parts. This is far more likely to occur with low specification compressors with insufficient duty cycle which are often purchased due to low cost. For redundancy in the system two compressors are often a better option. In Dryer failure the dryer, which functions to remove moisture from the air system, eventually becomes saturated and unable to perform that function. This causes moisture to build up in the system and can result in damaged air springs and/or a burned out compressor.


ECAS problems

The ECAS computer can, using pre-programmed criteria to detect a fault, disable the system into "Hard Fault Mode" which lowers the vehicle to the suspension bump-stops, leaving it usable with radically reduced performance until repaired. Many enthusiasts use diagnostic devices such as laptop and hand computers running specially developed software to clear spurious faults and avoid the need for repair. Some manipulate the sensors to set the vehicle to a particular ride height at all times by adjusting the lever ratio on the height-sensing devices, or a supplementary ECU to "fool" the system. Leaks in the system, often due to main seal wear caused by excessive duty cycle, can cause premature compressor failure.


Use on coaches and buses

The current market of buses have suspension system consisting of either mechanical or air suspension system. Compared to its counterpart, air suspension system has significant benefits. Vehicle height can be maintained at a particular value irrespective of its load by varying the pressure. Standard coaches also have a system called ferry lift. This allows the air suspension to be raised above the normal ride height level to aid loading and unloading the coach on and off ferries due to their steep ramps and risk of grounding out, but can also be used on rough ground or on steep crests. Although the ferry lift may be installed on some buses, the Kneel Down facility is more common on public transport buses. This helps reduce the step height for easy ingress of passengers. The Kneel Down facility is also used when using the built-in wheelchair ramps. Due to several advantages, air suspension has been extensively used in commercial vehicles since 1980.


See also

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Leaf spring A leaf spring is a simple form of spring commonly used for the suspension in wheeled vehicles. Originally called a ''laminated'' or ''carriage spring'', and sometimes referred to as a semi-elliptical spring, elliptical spring, or cart spring, i ...
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Coil spring A selection of conical coil springs The most common type of spring is the coil spring, which is made out of a long piece of metal that is wound around itself. Coil springs were in use in Roman times, evidence of this can be found in bronze Fib ...
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Torsion bar suspension A torsion bar suspension, also known as a torsion spring suspension, is any vehicle suspension that uses a torsion bar as its main weight-bearing spring. One end of a long metal bar is attached firmly to the vehicle chassis; the opposite end term ...
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Automotive suspension design Automotive suspension design is an aspect of automotive engineering, concerned with designing the suspension for cars and trucks. Suspension design for other vehicles is similar, though the process may not be as well established. The process en ...
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Self-levelling suspension Self-levelling refers to an automobile suspension system that maintains a constant ride height of the vehicle above the road, regardless of load. Purpose Many vehicle systems on a conventional vehicle are negatively affected by the change in attit ...
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Hydropneumatic suspension Hydropneumatic suspension is a type of motor vehicle suspension system, designed by Paul Magès, invented by Citroën, and fitted to Citroën cars, as well as being used under licence by other car manufacturers, notably Rolls-Royce ( Silver Sha ...
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Dashpot A dashpot, also known as a damper, is a mechanical device that resists motion via viscous friction. The resulting force is proportional to the velocity, but acts in the opposite direction, slowing the motion and absorbing energy. It is commonly us ...
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Active suspension An active suspension is a type of automotive suspension on a vehicle. It uses an onboard system to control the vertical movement of the vehicle's wheels relative to the chassis or vehicle body rather than the passive suspension provided by large sp ...
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Double wishbone suspension A double wishbone suspension is an independent suspension design for automobiles using two (occasionally parallel) wishbone-shaped arms to locate the wheel. Each wishbone or arm has two mounting points to the chassis and one joint at the knuckl ...
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Height adjustable suspension Height adjustable suspension is a feature of certain automobile suspension systems that allow the motorist to vary the ride height or ground clearance. This can be done for various reasons including giving better ground clearance over rough terrain ...
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Strut bar A strut bar, strut brace, or strut tower brace (STB) is an automotive suspension accessory on a monocoque or unibody chassis to provide extra stiffness between the strut towers. With a MacPherson strut suspension system where the spring and sho ...
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Sway bar An anti-roll bar (roll bar, anti-sway bar, sway bar, stabilizer bar) is a part of many automobile suspensions that helps reduce the body roll of a vehicle during fast cornering or over road irregularities. It connects opposite (left/right) whee ...


References


External links

* * {{Chassis control systems Automotive suspension technologies Automotive safety technologies Auto parts Mechanical power control