Weekly tire pressure checks might seem unrealistically ambitious, but given what's at stake in terms of tread wear and tire life, it's a worthwhile goal. Regular tire inspections should, obviously, include pressure checks.
The more frequently you do them, the better the chances of saving a slow leaker.

Tire life decreases exponentially with underinflation. According to The Technology & Maintenance Council's RP 235A - Tire Inflation Pressure Maintenance, running a tire 20% underinflated shortens its life by about 12%. Running a tire 30% underinflated lops about 30% off its expected service life. It only gets worse as pressure drops.

TMC's RP 235A recommends using a high-quality tire gauge, calibrated regularly from a master gauge to ensure accuracy. As for the actual operating inflation pressure, users should consult the Load and Inflation tables relating to particular tire sizes and anticipated loads. Interestingly, a typical 22.5-inch low-profile tire run in dual configuration is considered properly inflated for the load carried on a 34,000-pound tandem grouping at only 75 psi. That same tire in a steer position requires 110 psi for the 12,000-pound load on a steer axle.

Overinflating tires in dual positions to 95 or 100 psi is acceptable, and it provides a margin of error for underinflation if pressure checks are not conducted regularly.

The biggest risk in dual tires is inconsistency. RP 235A notes that a pressure differential of just five psi across the tires in a dual set creates a difference in circumference between the tires of up to 5/16 of an inch, and that difference in circumference increases with a wider pressure differential. Two tires of different circumference will not cover the same distance over a given number of rotations, but because the wheels are bolted together, the tires will scrub along the road, causing rapid and irregular wear.

From the March 2012 issue of HDT

About the author
Jim Park

Jim Park

Equipment Editor

A truck driver and owner-operator for 20 years before becoming a trucking journalist, Jim Park maintains his commercial driver’s license and brings a real-world perspective to Test Drives, as well as to features about equipment spec’ing and trends, maintenance and drivers. His On the Spot videos bring a new dimension to his trucking reporting. And he's the primary host of the HDT Talks Trucking videocast/podcast.

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