In 1888, John Dunlop put air inside a flexible donut and made a fortune. His invention mostly remains misunderstood even to this day. By encasing pressurised air, the tyre was made and modern vehicles became possible.
The ‘pneumatic tyre’ via air pressure supports every vehicle. Tyres sit between your vehicle and the road. Without air you have worthless rubber. Tyres provide the envelope and the traction surface but it’s the air pressure within them that supports the load. Air pressure also works as a spring and damper – an excellent one provided the pressure is at its optimal level.
What is the secret?
The tyre air pressure must be at the optimal level or the tyre is compromised. The contact patch, the rubber that touches the ground, is the key every tyre engineer aims for with their designs. The ambition is an even contact patch, the full width of the tyre, and spread fore and aft in a nice circular or oval shape. The size of the tyre contact patch, often called the “footprint”, depends upon the load and tyre air pressure. Increase the load, and the footprint will increase. Increase the pressure, and the footprint will shrink.
For each tyre, there is one optimal footprint that provides the best compromise between tyre life, tread life, rolling resistance, traction, ride, and vehicle control for that road surface. Any other footprint will degrade most of the above. Too much tyre pressure and the edges of the tyre lift off the road. Then, only the centre part of the tyre is touching, and you lose traction and tyre life. Too little air and the contact patch lengthens, the load on the edges increases, deflection increases, and at speed, this flexing creates heat, which damages the tyre. Another concern is reduced lateral stability. The vehicle wallows, floats, doesn’t steer as well, and it becomes similar to driving on a flat tyre. The air pressure must be balanced by the load. And the load must be balanced by the tyre’s air pressure. Every time you change the load, you must change the tyre pressure.
The key
The optimum inflation pressure is unique to each vehicle and set of operating conditions, such as load, speed, and terrain. Using AIR CTI (Central Tyre Inflation) gives you the safety, control and savings necessary, by balancing tyre pressure to the job, the load and terrain, to quickly provide daily savings using optimal tyre pressure(s).
Trucks are designed to carry a load. When the load varies, as required by the job, the load on each tyre will change. The steer tyre load usually doesn’t change much, as the engine and cab are integral. The load on the other tyres, including drive and trailer tyres change regularly. Very few trucks operate at the same load all the time. Efficiency, safety and tyre longevity cannot be achieved if tyre pressures remain at a single fixed value only set when tyres are cold. When operating with variable loads in highly variable temperatures, cold and hot pressures play a part in optimal tyre pressure management for best safety outcomes.
All properties of a tyre are influenced by its pressure e.g. vertical stiffness, handling, performance, ride comfort, rolling resistance, speed at which aquaplaning occurs etc. With the correct inflation pressure, the vehicle and the tyres will achieve optimum performance – improving safety, reducing wear and decreasing fuel consumption by reducing rolling resistance.
Under inflation reduces lateral grip, increases aquaplaning and increases fuel consumption. Extreme underinflation leads to large deflections that causes excessive heat build-up and internal structural damage that will eventually lead to tyre failure, often catastrophic.
Over inflation increases stopping distance, reduces traction, cornering grip, vibration and driver stress.
Savings
Optimal tyre pressure reduces our environmental impact. Roads last longer, gravel roads and tracks don’t break up so soon. Potholes, corrugation, dust, ruts, are all reduced when the correct tyre pressures are used.
Corrugations are caused by high pressure tyres, and are actually ironed out by low pressure tyres. Better traction, better ride and handling, combined with better roads, lower your costs and improve trip times.
The optimal tyre pressure is also the best compromise between traction, rolling resistance, inherent heat buildup, handling and ride quality.
Air is free
AIR CTI systems use air in tyres for amazing results. The driver can allow for changes in load and road conditions by pressing a button to select a new target pressure. AIR CTI has a significant number of advantages over the basic Tyre Pressure Monitor System – TPMS – sensors. Vehicles fitted with AIR CTI use their integral compressed air source to maintain a targeted tyre pressure without driver intervention. Pressures are sampled at a high rate and keep the tyres to within a few psi of the selected target. Pressure surges caused by elevated road temperature are automatically contained.
Tyres are grouped into zones of control so that pressure adjustments can affect a single tyre group, or the entire vehicle. Should a tyre leak develop mid-journey, the AIR CTI system will warn the driver while continuing to maintain the target pressure. Minor tyre problems can be dealt with later under safe working conditions and not on the side of a busy road. If more traction is needed, the driver can select a lower tyre pressure for increased traction, then complete their delivery objective.
Where dual-tyres are present, air flows between inner and outer tyres are coupled together so that load sharing can be maintained, regardless of the camber of the road.
AIR CTI also incorporates speed sensors, so when a speed threshold is reached, systems automatically shift to a higher pressure preference.
This ensures loaded vehicles at highway speeds always operate at the recommended target pressures. While TPMS monitors are a useful tool for a small investment they are very labour intense. TPMS only informs drivers of pressures, they do not introduce pressure change without manual intervention.
AIR CTI is designed and tested over decades and the entire system is guaranteed for 500,000km or three years.
For more information, visit aircti.com.
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