TTI columnist Greg Smith discusses how to detect and communicate tire durability

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Consumer tire durability has always been a concern in the tire industry and this has been worsened by the often-poor road conditions that are common in winter months. Tires need to operate in hostile and unpredictable environments, so manufacturers design them to be as durable as possible. But this is only part of the issue. Equally important are attempts to detect durability issues and communicate these to the vehicle and the driver. Flaws such as sidewall scuffs, and torn rubber caused by bumps and potholes can, in some cases, create serious safety concerns. Yet despite this, it is difficult to encourage car owners to check their tires – most just assume that the tires are fine and drive away.

For this reason, vehicle and tire manufacturers have developed various systems to mitigate these issues and detect punctures. These can be simple systems that use wheel speed sensors to identify if one tire is rotating faster than the others – if one is turning faster while the vehicle is traveling in a straight line, that tire must have a lower radius, which is indicative of lower inflation pressure.

However, these systems have limitations. They look at the relative speeds of the wheels – but if all four tires have the same slow puncture, they will rotate at the same speed and the system will not detect any of the punctures. Furthermore, the deflated tires will still have the same circumference while the radius will be lower – as tires are deformable objects rather than solid cylinders, the rules of common geometry and the ratio of pi do not apply in the same way. As a result, detecting punctures in this way will sometimes not work at all. In addition, these systems may be able to detect a puncture, but they are unable to detect a durability issue before it leads to a puncture.

A better system is the more advanced TPMS. These are physical pressure sensors mounted to the wheel that directly record the inflation pressure and transmit that to the car. Unlike using the wheel rotational speed, this measures the actual inflation pressure, so a puncture can be clearly identified via a loss of pressure. This technology is becoming more common in new cars but, as with the indirect wheel speed systems, is unable to detect anything other than inflation pressure – once again, they are unable to detect a durability problem before it leads to pressure loss.

More recently, tire sensor technology is moving further toward smart tires, which include an accelerometer mounted to the inside. These can provide additional data to the vehicle pertaining to grip levels, temperatures, vertical loads and so on. This can be used by the vehicle to adjust traction control and stability management systems. Theoretically, the accelerometer could also be used to detect an out-of-balance wheel and tire assembly, indirectly detecting a durability issue. Again however, any sidewall damage, delamination, or similar, is not detected directly.

The challenge remains: how can these durability problems be directly detected and communicated to the car and the driver? It’s a complex issue to address. One theoretical idea is a wire molded into the tire, just under the tread and sidewall. A small current could then be passed through that wire, with any break in current suggesting sidewall damage or similar. Such a system would, however, add to the manufacturing cost of the tire, and would also require establishing standardized communication between the tire and the car. An alternative idea could be a vehicle-mounted optical system that scans the tread and sidewall surface looking for defects. Such a system could work across any tire fitted to the car – but is probably not feasible using current technology, due to the costs and high sampling rate needed to scan a rotating tire up to high speeds. I’m sure many readers have alternative ideas, but the challenge is there, and the need remains. How do we robustly identify tire damage before it leads to punctures, or even worse, a potential blowout?

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