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BIG RIG BASICS JOHN BAXTER Rolling Along Regular tire inspections go a long way in cutting tire costs and staying out of trouble with the DOT ires are the second largest expense in running a truck, after fuel. Inspecting them care- fully will tell you how well the truck’s suspension and steering systems — and you — are taking care of them and help you head off a lot of expensive repairs. Frequent inspections also will allow you to replace or retread them before they wear enough to get into trouble safety-wise. T 2 1 2 First, measure tread depth to determine how worn each tire is. For each tire, hold the body of the gauge in one hand, then pull the stem all the way out of the gauge body. Rest the gauge on the tire with the stem down in one of the grooves and the flange flat on the TIRE INSPECTION Required tools: Tire tread depth gauge, tire pres- sure gauge and high-pressure air supply Level of difficulty: 5 (on a scale of 5-10) Time required: 45 minutes 28 TRUCKERS NEWS JULY 2011 5 tread surface on either side of the groove. Gently push down on the body of the gauge until it touches the tread on either side. 3 Without disturbing the stem, remove the gauge and read the number sitting right above the edge of the gauge body. Note that there are scales for both mm and 32nds of an inch. The 32nds of an inch is the one to read. The bare minimum for drive and trailer tires in roadside inspec- tions is 2/32, and 4/32 is the min- imum for steer tires. Replacing or retreading earlier helps prevent 3 6 4 5 6 damage to the casing as well as reducing on-road failures. Repeat for the two steer tires, all eight drive tires and, if you have a trailer, all eight trailer tires. Part of daily inspection is a pressure check. You can nor- mally read the recommended pressure off the sidewall. Always check tire pressure when cold — before starting out. Fully inflated tires run cooler, last much longer and use less fuel. Remove the valve stem cap, then force the pressure gauge snugly over the valve stem. Read 1 JOHN BAXTER