A deeper look at automotive air springs

Why buying a quality product does make a difference…

How do air springs work?

An air spring consists of a compartment that is filled with pressurised air and a rolling piston which is connected to the axle of the vehicle or integrated on the suspension strut.

The rubber sleeve is safely secured between the two components with high grade steel crimping rings for durable, airtight construction. Together they form the ‘active area’ for the pressurised air. The ECU uses several inputs (e.g. height sensors, vehicle speed, acceleration sensor) to calculate whether the air spring should inflate or deflate air to obtain the predetermined ride height.

Although an air spring is a wear and tear part, it can cope with high and low temperatures and has a high resistance to the constant abrasion of dirt and road debris. Arnott uses elastomer from respectable OEM manufacturers including Continental ContiTech, Vibracoustic and Goodyear. The sleeve construction is made with high quality elastomer material and consists of a 5-layer multi-ply design to provide a long-lasting structural integrity:

• Outer elastomeric layer
• Cord layer
• Intermediate elastomeric layer

• Cord layer
• Inner elastomeric layer

Air spring characteristics

A conventional coil spring has a linear spring rate. This means that the same compression force is needed to compress it during the complete stroke. It can be tuned to progressive behaviour by changing the distance between the turns and/or varying in the thickness of the steel.

An air spring behaves differently. The force that is required to compress an air spring increases exponentially through the stroke. This means more force is needed to compress the air spring near the end of the stroke, resulting in an overall comfortable driving experience.

The spring behaviour can be adapted to a more comfortable or sportier ride by changing the angle of the rolling piston. This is one of the reasons that a passenger car’s sport (air) suspension system usually features a different air spring than the standard (air) suspension for the same model.


Air spring systems automatically level the vehicle, so the spring travel stays identical. This is very convenient when heavy cargo is transported in the boot. By comparison, a coil spring system is less comfortable, can be unstable and is more likely to ‘bottom out’ on rough roads or uneven surfaces (e.g. potholes).

By reducing the air inside the air spring, the ride height lowers at high speeds. This brings the vehicle closer to the ground decreasing the drag coefficient und thus reduces fuel consumption.

An inherent benefit of an air spring is that it naturally isolates the passengers from road harshness, resulting in a smooth and comfortable ride. Most car owners describe this as the biggest advantage of driving a vehicle with (factory) air suspension.

Engineered to ride, built to last

During the development and testing phase of a new air spring, Arnott thoroughly investigates the original construction and design and looks for possible engineering or quality flaws. If present, the design is adapted and improved to eliminate those. Arnott’s designs often enable easier or fail- safe installations. After the development stage is finished, the product undergoes extensive road-testing (>3000 miles), durability testing, and burst testing to prove it meets the highest standards.

Although some cheap aftermarket air springs might look identical to the original part at first sight, the differences can be quite substantial. Making concessions – such as using inferior rubber, lower grade parts and /or consolidation in piston design – can result in lower burst pressure, difficult fitment, impaired damping comfort and more NVH (noise, vibration, and harshness).

Email: info@arnotteurope.com Web: www.arnotteurope.com

Justify suspension work by using free app

KYB has updated its Suspension Solutions mobile App and now provides detailed, part specific technical advice for suspension jobs, free of charge. The technician can either enter the car make and model, the VIN number, or the registration number to see the KYB part numbers required and a detailed technical bulletin for each job. This includes an illustrated step-by-step guide to fit the part, as well as the tools required (and relevant torque settings), and an estimate for the time needed to complete it. If there is a KYB fitting video available for the reference, this will also be provided. 

“We felt this feature was the next step for the KYB App”, explains Jordan Day, Marketing Manager for KYB Europe Aftermarket, “the App now helps with all the main stages of replacing suspension – helping to find the part number and fitting the product, helping the technician with proposing a suspension job to a motorist, and also following up the job.”The KYB App has currently been downloaded over 7,000 times across Europe. One feature allows the technician to suggest suspension work to a customer – the technician assesses the vehicle and inputs the ‘symptoms’ into the App, attaching a picture if required. The App then takes this information and creates a specific vehicle report, which is text to the customer, all for free. This report contains a button to “Call the workshop” – on average, this button is clicked by the motorist 1 in 4 times. Another feature allows the technician to take before and after photos, which can be added to a vehicle report that is text for free to the customer. The report explains the work that has been done and the benefit this will have on the vehicle and shows them the pictures of the old and newly fitted components. 

The KYB Suspension Solutions App is free to download and free to use, available in 20 European languages and fully customisable, so all reports sent out feature your workshop’s name, contact number and logo. For those who have already downloaded the App, simply update the App as normal to add the new fitting instruction feature. The App can be downloaded from the App Store and Google Play. 

Tenneco supplies suspension on Jaguar I-PACE all-electric SUV

Tenneco is supplying suspension components for the new Jaguar I-PACE all-electric luxury crossover SUV. The I-PACE  features Tenneco’s passive front and rear dampers, coil and air spring suspension modules, engineered to improve ride performance and stability.

“These suspension modules incorporate designs and materials that offer important benefits for all-electric vehicles such as light-weighting, underbody space savings and simplified vehicle integration.” said Neville Rudd, Senior Vice President, Tenneco Global Ride Control.

Tenneco’s suspension modules include plastic spring seats, an aluminium top mount and other lightweight components that can help offset the weight of electric motors and batteries, offering improved vehicle performance.

Mobile app justifies repairs to customers

The KYB Suspension Solutions App helps workshops explain to customers why their shock absorbers need replacing and can be easily customised with your garage details. It is available as a free download from the App store and Google Play.

A text message is sent to the customer explaining any worn or damaged components in their vehicle’s suspension. It also links to video clips which explain the dangers and risks associated with worn shock absorbers, coil springs, mounting and protection components. The app can be used to show the completed repair, with a before and after photo of the work carried out.

The app was designed to help workshops raise their profile and increase sales by educating customers on the role suspension components play. Marketing Manager Jordan Day says there are currently over 700 users of the app in the UK, he states: “So far we have had over 2,000 vehicle inspection reports sent out, with just over 400 calls made from the vehicle report back to the garage, by the car driver using the click to call feature. This is a rate of 1 in 5 people immediately calling the garage back – a number that will in real life be bigger, when taking into account those that read the report and then call the mechanic back by calling them from their contacts.”

KYB welcomes any feedback on suggested improvements and new features.

The supplier also introduced a 360 safety video back in November to enable workshops to show customers the difference in handling with new and defective shocks. We have several KYB VR headsets available for garages wishing to try this out, email nicola@autotechnician.co.uk if you’d like a pair.

Autotechnician reader Anthony Pickering gave them a go: “I used the 3D headset and the KYB YouTube video did highlight the importance of replacing shocks. The video in 3D with full panoramic view was good once I got to grips with it. This could be the future of information videos, and possibly training videos.”

Read more: KYB discusses the development of the double hydraulic stops system, used on the 2017 Citroën C5 Aircross on www.autotechnician.co.uk.

KYB introduces virtual reality safety video and mobile app for workshops

KYB introduces a virtual reality safety video and a free mobile app, to help workshops justify suspension replacement.

Screen Shot 2017-12-10 at 15.50.33KYB Corporation is Japan’s leading manufacturer of hydraulic products and produces around 57 million shock absorbers each year for OE and aftermarket customers around the world. Its technology can also be found in aircrafts, and marine vehicles and it has developed dampers, used in Japan’s skyscrapers to keep them standing when earthquakes strike.

Autotechnician, alongside other journalists from across Europe, gathered at its newly expanded shock absorber plant just outside Prague in the Czech Republic to witness its manufacturing expertise and to preview two workshop initiatives that should help justify suspension work to customers.

We are shown around its shock absorber and coil spring plants and its clear to see absolute precision is demanded from staff, tooling and processes, with Original Equipment and aftermarket products being produced on the same manufacturing lines.

Over the past year, KYB has conducted extensive research among its European workshop customers and within focus groups around the UK so the company could better understand the needs of the end user. Technicians and workshop owners were asked by an independent adjudicator for their opinions on the aftermarket in general, steering and suspension work and suggestions for what could make their lives easier. One comment was mentioned time and time again, workshops felt they needed help to explain the risks of driving with defective shock absorbers as the gradual decline process makes it a hard sale to customers. KYB has developed two new tools to educate customers and justify suspension work.


Screen Shot 2017-12-10 at 15.50.52The KYB Suspension Solutions App will help workshops explain to customers why their shock absorbers need replacing and can be easily customised by each garage using it. It is available to download for free from the App store and Google Play.

The text message received by the customer explains what issues have been identified with their vehicle’s suspension and which components need to be replaced. It also links to video clips which explain the dangers and risks associated with worn shock absorbers, coil springs, mounting and protection components. The app can also be used to show the completed repair, with a before and after photo of the work carried out.

The App was developed to explain the safety critical role which shock absorbers, coil springs, mounting and protection components play on a vehicle. Marketing Manager, Jordan Day, explains: “Feedback on the demo version was extremely positive and I am confident that this new mobile App will support our garage customers, helping them raise their profile with their customers and increase their sales”.


If motorists could go on a test track and experience the difference in handling with new and defective shocks, there’d be no problem selling suspension work – KYB has entered the world of virtual reality to provide the next best way to demonstrate the dangers of worn shock absorbers.

Viewers can use special VR glasses to watch the 360⁰ safety video where they will experience a product test of old versus new shock absorbers. The video uses the new virtual reality mode feature offered by YouTube and allows the viewer to turn their head in any direction as if they were in the car with the driver. *We’ll be giving away free headsets in the coming weeks via our Facebook page so you can experience this for yourself.

The video shows two identical vehicles doing a slalom test to evaluate the steering and control of the vehicle at 50kph and an emergency braking test at 70kph. One vehicle has covered 80,000km and has worn shock absorbers, the other has new KYB shock absorbers.

It is easy for the viewer to see the differences in performance, with the driver’s body angle and steering control significantly improved on the vehicle with new shock absorbers. On the braking test, the stopping distance with new shock absorbers is improved by almost a full vehicle length. This is more than half the width of a typical pedestrian crossing, so could mean the difference between stopping safely or hitting a hazard. At various points, the video is paused, and measurements drawn to clearly show the difference new shock absorbers have.

Marketing Manager, Jordan Day, comments: “I was the driver of the vehicles used in this test, and I was surprised just how dramatic the improvement in handling and control was with the new shock absorbers. I urge technicians to recognise when shock absorbers need to be replaced and to use this video to help their customers understand the dangers of worn shock absorbers”.

KYB will be giving garages cardboard VR glasses in order to share the 3600 viewing experience with their customers.


Advice to promote successful suspension repairs

Multi-link suspensions have largely replaced conventional wishbone suspensions, increasing driving dynamics and comfort. The modern design, explains TRW, features one or both wishbones broken down into multiple components, so that significantly more moving parts are installed.

The distance between wheel centre and steering axle – the so-called disturbing force lever arm – is relatively short. This allows disturbing forces (propulsive, braking and lateral guiding forces) to be kept away from the steering as much as possible. However, the joints move closer to the brake, which automatically exposes them to higher temperatures, resulting in significantly higher demands on the installed rubber sleeves and plastic bearing shells, as well as for the grease used.

More moving parts also means more joints connecting the parts, this results in a higher sum of ‘moments’, which are divided into breakaway torque and running torque. Breakaway torque results from the force required for setting the ball pin into motion from its resting position. The running moment results from the force required for rotating the ball pin or moving it back and forth in the joint.

Development engineers try to keep these moments as small as possible as this ensures, for example, that after cornering the front axle returns to the centre position independently and smoothly and that the suspension responds more sensitively. Today, so-called low-friction ball joints are used that have a substantially lower friction moment than previous types.

While a smoothly moving ball pin used to indicate increased wear of the ball joint, this is no longer the case. Modern ball joints have distinctly lower breakaway torques and running torques.


The product specifications defined for a multi-link suspension are determined during extensive test procedures on a test bench as well as in the vehicle. The associated moments (running torque and breakaway torque) as well as the damping properties of a joint always have to be considered within the overall system.

The influencing factors for steering systems, suspension, springs, brakes and tyres are extremely important for the functioning of the overall vehicle and for vehicle safety. Altering individual components and specifications is only permitted with consideration of the overall concept and always requires approval from the vehicle manufacturer.

Screen Shot 2017-11-29 at 18.41.28MAINTENANCE AND REPAIR

Mechanics should observe several points when replacing individual components.

When replacing a ball joint, the eye and the rubber contact surface in which the joint is installed have to be cleaned and any rust removed. The contact surface must be free from rust or the rubber sleeve will rub against the rough surface and leak. Dirt and moisture can enter the joint, which leads to premature joint failure.

During installation, it has to be ensured that the corrosion protection layer of the circlips is not damaged, as rust causes them to lose their spring force, allowing moisture ingress into the joint, significantly affecting service life.

Never tighten the ball joint with an impact wrench. There is a risk the ball pin could start to rotate so fast that the plastic bearing shell becomes deformed by the frictional heat, leading to play in the system. Furthermore, the tightening torque can be exceeded, causing the ball pin to move too high into the eye of the stub axle. This means the rubber sleeve can no longer fulfil its sealing function, allowing dirt and moisture to enter into the ball joint.

The rubber bearing on a control arm may only be tightened when compressed and without load to avoid twisting and therefore applying pre-tension to the bearing.

The installation errors described here can lead to premature wear or even failure of the replaced part. Garages should always carry out a wheel alignment after replacing suspension parts, even if only axle components were released. If these simple rules are followed, all suspension repair work can be carried out successfully.