Proper Inflation

Max Kvidera | July 01, 2011

Maintaining the ideal air pressure is the most important step in keeping tires in peak operating condition.

Checking your tires’ pressure regularly is like exercising – you know you should do it, but it’s easy to put it off.

Tire professionals say there’s a huge payoff for sticking with this routine. It will head off irregular wear that can reduce tire mileage, preserve the casing for retreading and enhance fuel economy.

The safety aspect of proper inflation is more important than ever. Not only does it help avoid catastrophic tire failure, it’s also a sensitive item with the Compliance, Safety, Accountability program. Under CSA, a tire violation carries among the highest severity weightings, adversely affecting your own or your leasing carrier’s score to a great degree. Tires are among the easiest pieces of your equipment for inspectors to check, too, says Guy Walenga, director of commercial products engineering and technology at Bridgestone/Firestone.

What is the proper pressure?

Ideal pressure varies with the weight you’re hauling. If you’re accustomed to hauling 80,000 pounds most of the time and you run few empty miles, choose pressure for the heaviest loads.

Many operators follow a standard of 100 psi in all tires. That may be adequate for steers, but it will make the drive and trailer tires overinflated by as much as 15 psi with a normal configuration of two tractor axles and two trailer axles, says Walt Weller, sales vice president at CMA, maker of Double Coin tires. Overinflation is “the lesser of two evils compared to underinflation,” he says.

50%  Tires within 5 psi of the recommended pressure.

Walenga recommends 110 psi for steers on a truck with a setback axle and a 12,000-lb. steer axle rating. “At 105, you’re technically underinflated,” he says. “For the steer axle you don’t have any leeway. You need the maximum pressure to make sure you’re carrying 12,000 pounds” effectively.

20psi   One out of 14 tires underinflated by at least that amount.

Under a full load, drive and trailer tires could be adequately inflated to about 75 psi, says Roger Stansbie, a director of truck tire engineering at Continental Tires, but most carriers and operators keep pressures much higher than that for better traction and to avoid letting pressures go too low.

20%    Dual-tire assemblies with pressures differing more than 5 psi.

Also, inflate both tires in dual pairs in the drive and trailer positions at the same pressure. To facilitate checking the pressure for duals, make sure the tires are mounted so the valve stem is at the 12 o’clock position on one of the tires and at 6 o’clock on the other, so as not to block access to the inner stem, Walenga says. If you don’t have that alignment, you’re less likely to make the effort to check the inside tire for pressure. “Slowly the inside tire will lose air – a pound or two every month,” he says, “and soon you will have irregular wear.”