By Jim Kerr

One of the key safety items on a vehicle is its tires: they provide directional control and stopping ability. They also have a big effect on fuel economy, and saving fuel seems to be on many drivers’ minds.

Looking after your tires takes little time and has many benefits.

According to the Rubber Association of Canada (RAC), under-inflated tires rolling on Canadian roadways waste enough fuel to power 275,000 vehicles for a full year. That’s an estimated 533 million litres of fuel this year alone! Under-inflated tires will add an extra 1.2 million tonnes of CO2 into the atmosphere, increase tire wear and negatively affect vehicle handling. A study commissioned by the RAC showed that one-third of Canadian vehicles had at least one under-inflated tire.

Newer vehicles have tire pressure monitoring systems to warn drivers if a tire is low on pressure, but these systems are not programmed to warn if a tire may be slightly low and wasting fuel. Visually checking tires isn’t good enough either. A tire that is dangerously low on pressure may look the same as one inflated properly. The only sure way to check tire inflation is to use a tire pressure gauge and use it often.

Tire pressure gauges are not expensive. For well under ten dollars, there are simple gauges with a sliding scale that is pushed out by the tire pressure. These gauges are fairly accurate but can wear, get gummy with dirt or become damaged. If the gauge shows erratic readings, then the gauge should be replaced. Digital electronic gauges are becoming more popular, although I find they sometimes don’t work well when stored in the glove box during a Canadian winter. They need to warm up first. The gauges used by those who need accurate tire pressure readings, such as race teams, are glycerin-filled round mechanical gauges with a flexible hose to reach the tire valve stem. These gauges may sell for $30 or more, but they make a great birthday or Christmas gift and will quickly pay for themselves in improved fuel economy. A driver who travels 20,000 km a year will save more than $100 in fuel if the tires are inflated properly.

With gauge in hand, checking tire pressures is a simple task, but there are right and wrong ways to do it. The first thing you need to do is locate the tire pressure specifications for your vehicle. These are found on a decal on the driver’s door or door jamb. Sometimes the decal is in the glovebox. If you can’t find the label, call your dealer for the information. Don’t inflate the tires to the pressure shown on the tire sidewall, as this is the maximum pressure the tires can hold, and inflating to this pressure will give a harsh ride and increase tire wear.

Tire pressure should always be checked when the tires are cold. The vehicle should have been sitting for at least three hours if you have been driving it. Tires become warm when driven and this heats the air inside the tire causing, the pressures to rise. This is normal, but pressures would show out of spec. If a tire has low pressure, it will create even more heat and cause pressures to increase that much more. In this situation, the low pressure tire may actually show the same pressure as other tires on the vehicle when hot, but this tire is operating too hot and could fail. If you have to drive to a service station to get air, drive slowly and no more than a couple kilometres so you can still test the tires cold.

Some tire shops fill tires with nitrogen gas rather than air, and the big advantage of this is that nitrogen gas is dry. Moisture in regular air can cause tire pressures to fluctuate more as the tires heat up. Nitrogen also seeps from the tire at about one-third as fast as air: In a month, a tire may lose one psi of air, while it would take 3 months for this to happen with nitrogen. Nitrogen is pricey, however, and checking tires at least once a month will ensure they are properly inflated even with air.

Whether you are concerned about tire wear, vehicle safety or improved fuel economy, checking tire pressures regularly can pay big dividends.

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