Truck News


Under Pressure

TORONTO, Ont. - After your paycheque and diesel, tires are probably your third greatest operating expense. But there are some simple steps to ensure a longer life for these valuable treads - and the m...

TORONTO, Ont. – After your paycheque and diesel, tires are probably your third greatest operating expense. But there are some simple steps to ensure a longer life for these valuable treads – and the most effective one among them requires nothing more than a $20 gauge to keep an eye on inflation pressures.

A 20 per cent drop below recommended air levels will shorten a linehaul tire’s life by 16 per cent, while lowering fuel economy by two per cent. Meanwhile, casings will begin to flex, increasing the likelihood of a trip to the scrap heap instead of the retreader.

Don’t forget the cost of downtime either. Forty-seven per cent of calls for roadside assistance are caused by tire-related failures, but half of those could be avoided by better preventive maintenance practices, according to Bandag. Quite simply, you’re under considerable pressure to keep an eye on tires from the moment that they’re installed to their final retread.

“Truck tires can lose up to two psi of inflation pressure per month, even if they’re brand new and properly mounted,” says David Scheklesky of Bridgestone/ Firestone Canada. More air can escape if the bead isn’t completely clean or properly coated with lubricant during mounting.

But if you think a whack to the sidewall will offer an accurate indication of pressures, think again. Ralph Beaveridge, the marketing director for Michelin’s truck tires, refers to a recent event when 12 officials from some of Canada’s largest fleets used hammers and clubs to thump at eight drive tires, as they tried to spot the one that had been inflated halfway. None of them could identify the problem tire without a gauge.

Linehaul drivers who are travelling from coast to coast should measure pressures once a week, suggests Goodyear technical marketing manager Al Cohn. “If you’re going a little off the road, mixed service, you should check more frequently.”

Of course, the gauge needs to give you an accurate reading, so he suggests using a calibrated model that’s regularly checked against a master version. (Keep in mind that dropping the tool can throw readings off by five psi or more.)

But it’s also important to consider the thermometer before acting on the numbers, since every 10F drop in temperature will be matched by a two psi drop in pressure.

“And never check it as soon as it comes off the highway,” Cohn adds. After 20 minutes on the road, a tire inflated to 100 psi can read 114 psi, so equipment has to sit for several hours before a reading.

Despite the benefits, it isn’t always easy to find the time to use a gauge, since it can take 20 minutes to measure each tire in a traditional tandem-tandem combination. Those working in logging or oilfield applications can encounter mud-caked valve stems, and there’s always the worry of jamming open a valve and losing air in the process of checking a tire, admits Greg Cressman, Yokohama’s deputy technical director. But a minor investment in flow-through valve caps will help you put gauges to tires without having to twist off their rubber counterparts in the dead of winter, and still protect the stems inside.

Each check can also give you an opportunity to watch for signs of irregular wear, and the best tool for that work is your bare hand. Simply run it across the face of the tread to feel for differences in the height of individual ribs or lugs.

Irregular wear can be costly, Beaveridge says. It was the killer of three out of every four scrapped steer tires studied by Michelin engineers.

But an alignment check at the first sign of trouble can be another affordable tool to extend tire life, Cressman adds.

A three-axle alignment check will typically cost less than $100, while an alignment involving just a few shims will cost $300 to $400. (The price increases if you have to replace tie rod ends or ball joints.) Consider the payback, he adds: “You’ve got 10 tires there at an average cost of $4,000.”

Rotating linehaul tires at 10,000 km can also pay dividends, Cressman says. “It seems to negate the impact of the onset of irregular wear.”

Some fleets will run steer tires in drive positions until they wear down by 1/32 to 2/32 of an inch, to establish a good wear pattern, Goodyear notes.

And since the rear tires on a tandem will often wear out faster than those in forward positions, drive tires should be rotated from front to back at least once before retreading.

The condition of other equipment will also make a difference in tire life. An improperly torqued wheel bearing can cause irregular wear, while worn shock absorbers can also shorten tread life, the manufacturer adds, so it’s important to replace worn components before they fail.

They’re all practices that will help you reduce operating costs – and that’s where the rubber hits the road.

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