Road-friendly air suspension systems increase the ability of trucks, trailers and coaches to transport loads by levelling the suspension, enhancing stability, control and safety over Australia’s diverse and demanding network of more than 870,000 km of public roads.
Use of these tough but comfortable systems – which also reduce noise and vibration – has grown exponentially over a generation in Australia, to the point where they have gone from being a comparative rarity to becoming an industry standard as drivers seek top performance on both sealed and tough unsealed roads, which still comprise more than half the total.
Air suspension systems now abound in the Federal Government’s lists of Certified Road-Friendly Suspensions prepared by the Department of Infrastructure, Transport, Regional Development and Communications. Suspensions on the list encompass the major OEM and specialist brands of worldwide manufacturers including in Australia.
“When we started selling air springs for trucks 40 years ago, they were more of a rarity than the norm,” says Russell Chown, of Air Springs Supply Pty Ltd, national distributor of Firestone Industrial Products, manufacturer of one of the world’s top selling air spring brands.
“I am told we had just a few pioneers in the road transport industry back then, who appreciated the technology through the seat of the pants, more than anything else, because air suspensions were far smoother compared with the harsher, clumsy systems that were commonplace on heavy vehicles at that time.
“But the industry as a whole quickly woke up to the fact that these suspensions could be kinder to the roads, as well as to them – and last for hundreds of thousands of kilometres. In well maintained cases, out past 600,000 km,” says Mr Chown, who is Sales Manager, at Air Springs Supply, which, through its national network, is a leading supplier of both vehicle and industrial air springs to industries including road transport, logistics, rail, mining and energy, manufacturing, construction and infrastructure and earthmoving and civil engineering.
Russell Chown of Air Springs Supply, which, in addition to providing the world’s top selling OEM air springs, also offers quality alternatives to a host of other major brands
These markets – which have continued to be served by Air Springs Supply throughout the Covid-19 pandemic – are major users of their ubiquitous Airride™, Airstroke® and Airmount® Firestone air springs and ContiTech air springs for coaches, prime movers and trailers.
Today, demand for air springs utilised in air suspensions for all types of heavy vehicles (including a vigorously growing market for 4wds and recreational vehicles) has grown in line with a world market that is now estimated by market researchers to exceed $A6 billion.
Mr Chown says that the tremendous distance travelled and safety achieved by OEM and after-market springs can be extended further with a preventative maintenance checklist (below) that takes just a matter of minutes and will save both downtime and money across major users of heavy vehicles, ranging from transport and logistics fleets through to mining, construction and individual users of articulated, rigid and on-road and off-road vehicles using air suspensions. The following simple checks will pay dividends (noting that users should never attempt to actually service the air suspension on a truck or trailer with the air springs inflated.
Circumferential cuts, left, can be caused by being fully extended for long periods or impact of in the compressed position. Loose girdle hoops, right, can be caused by running at extended positions with low air pressure.Preventative Maintenance Checklist
- Inspect the Outside Diameter (O.D.) of the air spring. Check for signs of irregular wear or heat cracking.
- Inspect air lines to make sure contact doesn’t exist between the air line and the O.D. of the air spring. Air lines can rub a hole in an air spring very quickly.
- Check to see that there is sufficient clearance around the complete circumference of the air spring while at its maximum diameter.
- Inspect the O.D. of the piston for build-up of foreign materials. (On a reversible sleeve style air spring, the piston is the bottom component of the air spring).
Holes in the side of the bellows (or the bellows area that rolls over the piston a reversible sleeve bellows, can be caused by factors such as structural interferences, including a broken shock absorber, loose airline, misalignment, worn bushings, no air pressure, foreign material such as sand or rocks, – or use of the wrong air spring. Off-centre bumper contact, right, can create faults similar to abrasion or bottoming out caused by factors such as worn bushings and improper suspension installation.- Correct ride height should be maintained. All vehicles with air springs have a specified ride height established by the O.E.M. manufacturer. This height, which is found in your service manual, should be maintained within 1/4″ (6.3mm). This dimension can be checked with the vehicle loaded or empty.
- Leveling valves (or height control valves) play a large part in ensuring that the total air spring system works as required. Clean, inspect and replace, if necessary.
- Make sure you have the proper shock absorbers and check for leaking hydraulic oil and worn or broken end connectors. If a broken shock is found, replace it immediately. The shock absorber will normally limit the rebound of an air spring and keep it from overextending.
- Check the tightness of all mounting hardware (nuts and bolts). If loose, re-torque to the manufacturer’s specifications. Do not over-tighten.
Concave bead plate, left, or over-extended air spring, right, can be caused by factors such as broken or defective shock absorbers, defective levelling vale, overloaded vehicle, pressure regulator set to low or use of an incorrect air spring that is too tall, Damage from over-extension can also be caused by defective uppers stops or an air spring that is too short.- Use the right cleaning media because use of incorrect media can cause damage and void warranties. In the case of Firestone, for example, approved cleaning media are soap and water, methyl alcohol, ethyl alcohol and isopropyl alcohol. Non-approved cleaning media include all organic solvents, open flames, abrasives and direct pressurized steam cleaning.
Mr Chown says users who find a fault exists using the checklist should please take corrective action to ensure that it is fixed properly – “It will save you both time and money and ensure ongoing safety.”
“Now more than ever it is important for safety and cost-efficiency to maintain the suspension of Australia’s hard-worked heavy vehicle fleet – including nearly 360,000 rigids over 4.5t GVM and more than 105,000 articulated trucks – which now have an average age of nearly 15 years.
“This is twice the average of leading European nations and three times the average of China and California, according to the Trucking Industry Council”. (reference?)
“So not only are Australian heavy vehicles working longer, particularly during the Covid-19 pandemic, they typically cover greater distances to keep up with constantly changing supply chains to deliver a greater range of urgently needed goods to far-flung urban and rural centres. Clearly safety and reliability are paramount for this vital job.”