AIR CTI’s Central Tyre Inflation System is an important tool allowing you to adjust your tyre pressures from the cab as you drive.
The cold tyre pressure you commence your journey with changes as your tyres heat and/or conditions change.
All properties of a tyre are influenced by its pressure, e.g. the vertical stiffness, the handling performance, ride comfort, rolling resistance, speed at which aquaplaning occurs, etc. With the correct inflation pressure, the vehicle and tyres achieve their optimum performance.
An optimally inflated tyre improves safety, reduces wear and decreases fuel consumption by reducing rolling resistance. Under inflation reduces lateral grip, increases aquaplaning, and increases fuel consumption.
Extreme under-inflation of a tyre leads to large deflections that cause 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.
Tyre grip is defined as the maximum horizontal force that can be transmitted between the tyre and road surface. A higher level of grip allows the driver to stop quicker, avoid accidents, reduces the chance of losing control over the vehicle, and improves the steering and braking potential of vehicles. If involved in an accident, it enables the driver to reduce speed before the collision to achieve a lower impact speed, which reduces the risk of injury.
With increased tyre grip, the risk of directional vehicle instability during steering and braking manoeuvres is also reduced.
Lightly loaded or empty semi trailers are considered to be the most dangerous, by insurance company reports, with jack-knifes a regular occurrence. Tyre inflations in these conditions are severely over-inflated, reducing the tyre footprint to 25 per cent of the correct footprint. Stopping distance was reduced by at least 15 per cent with optimal tyre pressures in tests done by ARTSA in 2013.
Jack-knifes happen when the drive tyres lose traction and the trailer pushes them offline. Trailer swing happens when the trailer tyres lose traction and slide outwards.
Both conditions happen when the truck is braking heavily, or when the traction level is low. Loss of traction of one set of tyres is the underlying cause. Bad brake balance, that over-brakes one or the other set of tyres and/or poor loading are the main causes. Over-inflated tyres increase the risk.
An example of poor loading is a tip or dump truck towing a plant trailer with an excavator. A heavy trailer, with no weight on the over-inflated truck drive tyres, is a common site on most roads. Almost all cases happen on empty trucks, where braking is overpowering, on severely over-inflated tyres, that provide minimal grip or traction. Poor conditions make life even riskier. Modern electronic braking systems virtually eliminate these accidents, although stopping distances increase considerably.
Optimal tyre pressure would substantially improve both cases, while reducing stopping distances.
The tyre road interface produces all the forces and moments used to alter the vehicle state through cruising, accelerating, braking and cornering. The footprint or contact patch with the road surface provides the traction required. The ideal footprint will have almost identical pressure on all points, limiting tread squirm while providing the best traction and tread life. To obtain the ideal footprint, the air pressure must balance the load correctly.
If the pressure is too high for the load, the footprint area will reduce, and the load distribution will be concentrated toward the centre of the tyre, reducing pressure near the edge, further reducing tread life. Tyre radial deflection will reduce, reducing absorption of impact, increasing vibration and shock transferral to the suspension and the rest of the truck. Impact from sharp stones or edges are much higher, increasing punctures, cuts, and staking.
Casing life reduces when over-inflated too. As retreading is a proven method of reducing costs, casing life is important. Traditional over-inflated tyre use increases tyre costs even further.
Dual tyres suffer a major design fault. Various factors increase the running temperature on one tyre more than the other, yet both are firmly bolted together and must rotate at the same speed. Any discrepancy in tyre diameters and/or pressures causes one tyre to attempt to travel farther than the other.
AIR CTI Central Tyre Inflation System is an important tool allowing you to adjust your tyre pressures from the cab as you drive. The cold tyre pressure you commence your journey with changes as your tyres heat and/or conditions change.
AIR CTI has been operational for decades as a family run business, developing and implementing improvements routinely to ensure the best customer outcomes. This continues. We are always happy to assist with any queries.
For more information, please contact sales@aircti.com or call AIR CTI’s sales manager Peter on 0409 899 916.
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