What's the best pressure for the tires in your fleet?

What’s the best pressure for the tires in your fleet?

Choosing the recommended tire pressure specification seems like a very simple process. There are load/inflation tables published by all the tire companies and easily found on their respective websites. Recommended tire pressure should always be based on the worst case load scenario for your vehicle. Even if you are running fully loaded only 10% of the time, it is still necessary to choose your tire pressure specification based on this heavy load scenario since air is what carries the load.

Using your vehicle weigh scale data, take the load for each axle and divide by the number of tires to determine the actual load/tire. These load/inflation tables are based on individual tire load and not on the axle load.

What can also be confusing is the fact that when using these tables is for every tire size, the tire pressures are listed for various loads when the tire is being run as a “single” and a different load capacity when the tire size is run as a “dual” configuration.

The maximum tire load at a specific pressure is the information molded during the manufacturing process onto both tire sidewalls. For example, the popular 295/75R22.5 Load Range “G” tire has a maximum load of 5,675 lbs. at 110 psi when run as a dual configuration. If the same size tire is a Load Range “H” design, then that tire has a higher load capacity. The 295/75R22.5 LR “H” when run as a dual is rated at 6,005 lbs. at 120 psi.

This additional 330 lbs. equates to about a 6% increase in load capacity per tire. There is no reason to spec a higher load capacity tire unless your vehicle load studies indicate that a LR “H” tire is required. Higher load capacity tires are typically designed with heavier gauge steel cord, which will have a price premium.

Using this same tire size 295/75-R22.5 LR “G” as an example, if you were running this tire on the steer position, then the “single” data line from the load/inflation tables is used to determine the proper tire pressure. In this case, the maximum load capacity is 6,175 lbs. at110 psi when run on the steer position. This calculates to 500 lbs. or an 8.8% increase in maximum load capacity when the tire is run on the steer position as a “single” versus the same exact tire run as a dual on either a drive or trailer position.Using these load/inflation tables will allow your fleet to choose the recommended tire pressure based on your actual loads.

When tires run at the recommended tire pressures based on your actual loads the tire footprint is optimal. A uniform tire footprint will lead to smooth, even wear and good fuel economy, as well as keeping the tire casing running cool in the process, which results in improved retreadability.

An underinflated tire will have an elongated footprint with more rubber on the road. There is approximately 18% more rubber on the road on a 295/75R22.5 tire that is underinflated 30%. There are many times when those inside dual trailer tires are measured to be at 70 psi versus the outside duals, which have 100 psi.

The longer footprint on an underinflated tire will increase rolling resistance and lead to a significant drop in fuel economy. In addition, underinflated tires will generate irregular wear, lead to early tire removal miles and generate an increase in heat which will hurt when it comes to the retreadability of the tire casing.

It is a good practice to work with your tire professional for assistance in choosing the optimum tire pressure for your fleet which will go a long way in reducing your tire expenses.

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