How tire monitors save money—and lives 

A huge wave of awareness is set to crest across Canadian drivers in the next two years as tire-pressure warning lights start flashing on our dashboards.

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A huge wave of awareness is set to crest across Canadian drivers in the next two years as tire-pressure warning lights start flashing on our dashboards.

Since 2007, all new cars sold in the U.S. have had mandatory tire pressure monitoring systems (TPMS) installed, and about 70 per cent of Canadian cars have followed suit.

The sensors for these systems have a lifespan of five to seven years (or 140,000 to 160,000 km), and then the warning lights will indicate when it is time to replace the sensors housed inside the wheel/tire assembly.

Before we all cry “cash-grab,” let’s look at why TPMS may be one of your prime safety systems. TPMS consists of a circuit board and battery, which sends information about tire pressure to the car’s main computer three to five times per second.

If the pressure drops 25 per cent less than the vehicle’s recommended pressure, a warning light on the dash is triggered.

An underinflated tire can lead to tire failure and/or loss of control while braking or cornering.

But even if the underinflation is not that severe, it hurts the wallet. An 8-per-cent pressure drop can shorten the average tire’s life by 15,000 km. And underinflation of just 5 per cent increases fuel use by 1 per cent.

A recent study found that half the vehicles in Canada have at least one tire over- or underinflated by 10 per cent, and 10 per cent have a tire underinflated by 20 per cent.

The American traffic safety board estimates that 660 people are killed each year as a result of underinflated tires.

There are two types of TPMS designs: the active, which use sensors and can transmit real-time information to the car’s CPU, and the passive, which have no sensors inside the tires.

Passive systems use the ABS sensors to measure wheel revolutions. When a tire deflates, it turns at a different speed than the other three and this triggers a warning.

Some active systems can display the tires’ psi on the dash, and even identify which tire has an issue. I’ve had the misfortune of watching the tire pressure counting down as air hissed out of one of my tires along Hwy. 400.

Kal Tire and Schrader International (a leading TPMS producer) are on a consumer awareness campaign to let drivers know the benefits.

“We’re finding that lots of drivers don’t know what TPMS is, and there is skepticism about its value,”says Casey Hull, director of retail products at Kal Tire. “Just like seatbelts and airbags, TPMS can save lives.”

Schrader vice-president Trevor Potter agrees.

“Drivers don’t yet understand the value of having a system that automatically detects low tire pressure, but that’s changed in the last few years. In the U.S. more people know what it is now and appreciate it.”

Schrader sensors consist of a circuit board, a pressure sensor, a radio transmitter an antenna and a battery. All of this is packed into a 5.5×1.5-cm plastic case attached to the inside of the valve stem inside the wheel.

The metal of the valve is cleverly used as the antenna. These units cannot be serviced, so when the battery runs out, the unit needs to be replaced.

Lou Mazzuca, a Kal Tire manager in Rexdale, explains that whenever a tire is changed, care must be taken to not damage the sensor attached to the bottom of the valve.

On most cars, the sensors must be reprogrammed after a tire change in order to convey correct information to the CPU. Even a tire rotation may need reprogramming of the sensors to tell them where they are located on the car.

Kal Tire insists that if a car is equipped with a TPMS and the owner buys a winter wheel and tire package, it will include sensors for the new wheels.

The cost of sensors has come down through more production and updated software by Schrader. It now offers two sensor models that cover all 170 operating systems in use by various auto makers. These EZ-Sensors sell for about $70 per wheel, including installation and programming.

In the past, some drivers have refused to buy sensors for their winter tires, and resorted to using black electrical tape to cover the resulting warning light all winter.

“Electrical tape is not a solution,” says Potter. “TPMS is a safety system.”

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