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4x4 Tire Pressure Pointers

Blown Out Tire
Trevor Reed | Writer
Posted April 1, 2012
Photographers: Judy Reed

Using Chalk Is An Easy Way To Perfect Your Tire PSI

You don’t need a tire blowout to have an excuse to upgrade your truck’s only contact points with the ground, but it’s good motivation. If you take this as an opportunity to upgrade the height and width to larger than the factory-equipped size, you can use chalk to make sure you don’t have too much or too little air pressure. Ignoring or just eyeballing the amount of pressure in your new tires can lead to premature wear and dangerous conditions such as excessive heat build-up, poor handling, and longer braking distances. Plus, you’ll get the best performance and fuel economy out of your truck when the tires are set up correctly.

Our family pickup is a ’70 GMC Sierra Grande ½-ton with the original 396ci big-block V-8 over the front tires, which travels only about 1,000 miles per year. After a decade of exposure on the driver’s side of the truck, the sun eventually took its toll on the sidewalls and caused a driveway blowout at the front left corner. The terribly out-of-style five-star aluminum wheels from the ’90s and mismatched front street and rear mud tires were upgraded to 31x10.5-inch All-Terrains all-around. The new gear was delivered pre-mounted and pre-balanced on some basic steel wheels. The bigger tires arrived with a good amount of air, but after testing using the chalk method explained in this article, it turned out they needed about 20 percent more pressure in each one. After the All-Terrains got up to the proper pressure, the pickup’s ride was better than it had ever been during the 36 years this GMC has been a part of our family. Here’s how we did it using just some chalk, a tire gauge, an air supply, an empty parking lot, and a little patience:


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If your truck has to sit outside, you should consider buying sun-resistant covers for the tires that are left exposed. We bought tire shades designed for use on a motorhome to fully cover the new oversize tires. The spare will also get a tire cover; it’s exposed to all the elements, as well as everything that gets loaded into the bed and the water used to wash out debris.