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On the Road

Why you need to be using truck tire inflation load tables

David Sickels is the Senior Editor of Fleet Equipment. He has a history of working in the media, marketing and automotive industries in both print and online.

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Yes, I know that you know that maintaining the proper tire inflation pressure is important. But other ideas surrounding the idea of proper tire inflation pressure are also important. And I can’t stress enough the importance of understanding that the inflation pressure doesn’t need to be a set number all the time – it needs to be a number that carries the amount of load.

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Here is a transcript of the video:

If you’re going about always filling all your tires to the same pressure all the time, you’re overlooking something crucial: It’s air in the tire that carries the load, not the tire itself.

When you have 60,000 lbs. rolling down the highway at 60 to 70 MPH, there are two things that matter: First, how much the tire sidewalls are flexing, because if they’re flexing too much, they build up heat and they could fail.

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The second is the shape of the tire’s contact patch. There’s about the width of two hands that makes contact with the ground, and you want to make sure that is the best possible shape for starting, stopping and turning. So, you’re managing the flexing of the sidewall and the shape of that contact patch through inflation pressure.

To keep the proper PSI in your tires you need to START with the right PSI – and that can vary by loaded weight.

When you’re trying to find that number, know that the steer axle is the most consistently-loaded tire on the truck because of the engine. A typical 80,000-lb. configuration has 12,000 lbs. on the steer, 34,000 on the drive tires and 34,000 on the trailer tires. Twelve thousand pounds on the steer axle is 6,000 lbs. per steer tire, but 34,000 lbs. over eight drive tires is only 4,250 lbs. per tire.

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Think about that. So, you need a full 110 PSI in a typical steer tire and even more if you’re running a heavy steer axle like a 13,000-lb. axle. You need quite a bit less than that on the drive tires.

If you’re trying to maximize your tire effectiveness, in this case the steer tires would be filled to somewhere around 100 to 110 PSI, and drive tires, fully loaded, would be around 85 to 90 PSI.

Many tire manufacturers publish inflation load tables to aid you in your fight against improper tire pressure. And you should be using these tables unless specifically directed by a tire manufacturer.

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To select the proper load and inflation table, locate your tire size then match your tire’s sidewall markings to the table with the same sidewall markings. But you can’t just take the pressure reading at any point. Instead, tire pressures should be set cold before the trucks leave the yard. Cold inflation pressure is most accurately measured when tires have been parked for at least three hours or driven less than a mile at a moderate speed.

When tire pressure is maintained at a proper level, it means you’re doing your part to promote safer driving conditions while optimizing the cost-effectiveness of your tire investment.

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