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Nuts & Bolts: Under Pressure

Posted in How To: Tech Qa on March 20, 2019
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I own a 2008 Chevy 3500HD dualie and recently had the tires replaced with the proper load range tires for the truck, which were a brand recommended by my local tire shop. The other day I took the truck in for an oil change and the technician asked me what pressure I wanted the tires set to. Since I haul a big trailer pretty regularly, I told him to set them to whatever the maximum pressure was on the sidewall of the tire. He came back a few minutes later and said the tire pressure on the sidewall was higher than what was recommended by the sticker on the door, and that if I had him set it to the sidewall pressure, that gas mileage and tire wear would suffer. I told him to go with the sidewall pressure anyway, but that got me to thinking . . . Should the technician go back to flipping burgers for a living or am I wrong?
Kyle S.
Via email, nuts@4wor.com

While the technician might have been simply following his training, we’d probably tell him not to retire his spatula just yet. Assuming the tires you chose match the recommended load rating for the truck (load range E or higher), then we would always default to the pressure that the tire manufacturer recommends because the recommendation is based on testing with that specific tire at the maximum load for which the tire is rated. The sticker on the door, on the other hand, represents the pressure recommended for the OE tires that came on the truck, which are probably different from what you purchased. We would be suspicious if the pressure on the sidewall was less than what was stated on the door, but not if it’s higher. Going by the pressure on the door on your new shoes can potentially underinflate the tire, which is potentially hazardous at maximum load.

We often recommend lowering tire pressure for better traction off the pavement, and sometimes on the pavement as well. The on-pavement recommendations are usually the result of putting a heavily rated tire on a lightweight vehicle, such as Load Range E tires on a Jeep Wrangler. The stated maximum pressure on the sidewall assumes a maximum load as well, but Load Range E is way more load capacity than a Wrangler can handle. Oversize tires often have beefed-up carcasses to deal with the larger sidewall of a bigger tire, but running an E-rated tire at max pressure on a Wrangler will do nothing but cause loose fillings. Lowering the on-road pressure to a more reasonable number on a lightweight vehicle actually gives a high-rated tire a better footprint and a vastly improved ride. But since you’re actually using your truck as it’s intended (hauling heavy loads), we would default to sidewall pressure.

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