Regulators under pressure!

Regulators under pressure!

By Adam Gosling:

The prime function of a pneumatic tyre is to contain the inflation medium. Every other function is secondary. Why are heavy vehicle regulators around the globe ignoring the absolute criticality of tyre inflation pressures for heavy vehicles?
As drivers we place high demands and expectations on our tyres regardless of the vehicle we are driving. When we sit behind the steering wheel we demand the tyres are ever ready to perform in an instant, ready to work within their capacity and sometimes beyond it. Who has heard a tyre squeal as it grabs for traction? Yes, many times a tyre is pushed beyond design capacity.
The humble tyre just goes along with our demands; it performs to the best of its ability even if that means the tyres’ ultimate demise. Our expectations don’t consider what surface the tyre is operating on, or what state the tyre is in. The tyre may have been left sitting for days, even months, and in an instant we demand it works.
For a heavy vehicle the tyre may be working at the upper end of its operating spectrum, it can go from standing still and cold to full speed and maximum load within minutes. The vehicle may be navigating bends that place high stress on the tread and casing. It may be that the start of the journey is only a taste of what is to come. A high speed run of several hours’ duration at full load in a high ambient temperature may be ahead. Sometimes a tyre will have to run for some days without much of a break.
The expectation of the driver is that the tyres will perform faultlessly, maintaining vehicle safety, maintaining economic performance, maintaining vehicle comfort. The tyres only require that they are appropriately maintained, and that does not mean just a cursory glance to make sure they are not flat!
Some regulators have focussed on the tread depth of a tyre. There is discussion, some of it from a naive perspective, some of it from an economic perspective, some from manufacturers protecting their turf, some from regulators who are pressured to reduce injury and damage our modern society has to come live with. As any motor racing driver knows a slick tyre, i.e. one without a tread pattern will outperform a treaded tyre in the dry by large margins. That’s right, a tyre without any tread pattern, a slick, yields superior performance on a dry road. It’s simple physics, a slick tyre has more rubber contacting the pavement. On road drivers don’t have the luxury of a racing car pit team with a set of treaded tyres ready to install every time it rains. To cater for the worst case a tyre experiences in road going duties a tread pattern is installed. Wet surfaces equal less traction, that’s a commonly accepted factor.

Tread pattern

The technology involved in designing an effective tread pattern is well beyond having a “pretty” pattern. Each pattern has to undergo extensive testing to determine the level of grip available over the many different levels of traction that a tyre on a road going vehicle will encounter. On a wet road the tyre tread pattern is required to drain the water from between the contact patch of the tyre and the pavement it contacts. The higher the speed the more water the tyre will encounter so a higher level of drainage is required. The grooves in the tread pattern provide the paths for the water to be pumped from the contact patch.
Aquaplaning is the term used when the contact between the tyre and the pavement is broken. When a tyre is aquaplaning it is effectively riding on top of the water, traction is zero, control is even less. For those who have driven on icy roads you will know the feeling, the dreaded feeling when the steering wheel goes limp, the vehicle moves in unexpected directions and hope is the only factor when it comes to feeling safe.
Having a tread pattern that will perform to traction requirements when it is new is expected. As the tyre wears and ages the tread pattern subtlety alters as the pattern wears. To gain maximum performance when a tyre is new the tread designer creates a different profile of the tread blocks through the depth of the tread pattern.
Current computing power has enabled tread designers to simulate the forces and stresses the tread experiences under various driving conditions to simulate the tyre’s performance throughout it’s life. This is high tech R&D; it costs but let me ask what price do you put on your personal safety?
The tread package in turn must adhere to the tyres casing to transmit the forces from and back into the vehicle. Modern tyre science is a complex art of compromise. A high traction tyre will more than likely yield a short life. A long life tyre will provide a reduced level of traction. At best tyre performance is a compromise between life and grip.
What is not a compromise, however, is the requirement for the appropriate level of inflation pressures. Regardless of what state the tread pattern is in a tyre will not perform to the driver’s expectations if the inflation pressure is not appropriate to the load and speed the vehicle is driven at.
The fatal events of 1999 in the USA brought the TREAD Act (2000) that mandated the use of tyre pressure monitoring systems (TPMS) on light vehicles. A light vehicle is determined to be under 4,500 kgs. The EU and many other jurisdictions followed the lead of the USA in realising the extent of under maintenance of the humble tyre and so mandated TPMS in their jurisdictions.
Many vehicles are largely operating within an urban setting, low speeds, not necessarily high masses in the vehicle. However, come holiday season many of the same vehicles are found heading out of the cities onto the highways for sustained high speed operations. More than likely there is extra load in the vehicle especially when a holiday adventure is undertaken.

Higher loads

When considering heavy vehicles, the loads imposed are higher, the speeds are often sustained for longer yet in the majority of jurisdictions around the globe tyres on heavy vehicles are not required to be inflated. Yes, you read that correctly. Unlike light vehicles heavy vehicles which impose greater forces and loads on their tyres are not covered by any mandate requiring their tyres be inflated to a safe minimum pressure. A light vehicle has a tyre placard which details the optional tyre sizes and specification (load and speed rating) as well as minimum tyre inflation pressures for various load conditions, i.e. just a driver, or the driver and passenger and luggage.
In any risk assessment process the outcomes when considering heavy vehicles in a loss of control event are substantially worse than the same for a light vehicle. A heavy vehicle has magnitudes higher inertia so take longer to come to rest, the braking forces required are magnitudes larger due to the increased mass a heavy vehicle supports.
It seems that the various regulators around the globe have all ASSuMed that tyres on heavy vehicles will be appropriately inflated. The only ASS in this equation is the one looking at a catastrophically failed tyre on the side of the road. It has been very interesting to listen to regulators and inspectors inform of their opinions that tyres are not very important to vehicle safety.
What connects the steering system to the pavement? What connects the driveline to the pavement? What connects the brakes to the pavement? The TYRES! So how can tyres not be a critical component of the steering and braking systems on our modern road going vehicles?
The autonomous vehicle (AV) industry is dragging the regulators into the current century. Tyres are actually becoming the information centre for vehicle performance. With high tech electronics active tyre pressures are fed into the vehicle control computers in real time. Tyre temperatures are recorded and provide data for vehicle control. Even the forces experienced by the tyres are being determined and fed into the control systems setting the bench mark for the level of power applied by the drive train. The tyres for an AV are the prime controlling factor in performance.
Until non pneumatic tyres become common place tyre inflation pressure maintenance is the hinge point for vehicle safety. If the tyre is not appropriately inflated for the load and speed it WILL NOT perform in the expected (or desired) manner.
Why do you as a driver expect magic to happen when you consider tyres? Check the tyre pressures before and when you are driving, just as you check your speed, the inside and outside temperatures, the GPS location of your vehicle. Without tyres working as you expect them to you may not safely reach your destination.

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