Reading the Rubber: What Your RV Tires Can Tell You

e’re all accustomed to replacing our tires as they wear out — that’s a given. However, RV tires aren’t always run to the point where the tread is nearly gone. Because of the way most outdoor enthusiasts use their RVs — on weekends and for extended trips during warmer weather — our rigs usually spend more time sitting than moving. As a consequence, the tires aren’t impacted by wear-and-tear; they are instead subjected to the sun’s heat and harsh ultraviolet rays.

The end result, however, can be the same: you’re driving down the highway and suffer a premature tire failure.

What happened? Like the asphalt when a vehicle is moving, the sun — and weather — will eventually degrade the tire to the point where it’s unsafe. That’s why most tire manufacturers recommend that RV tires be replaced every six years no matter how much tread is left.

The problem is that most RVers don’t know how old their tires are — especially if they bought a pre-owned vehicle.

That’s okay: All the information you need is right under your rig. Tire sidewalls are stamped with a wealth of information, including the wheel size, sectional width, load rating, maximum inflation pressure and the date of manufacture. All of these are important — especially the last one. By knowing how to decipher these hieroglyphics and adhering to industry standards, you’ll increase your chances of traveling without suffering an unforeseen tire problem, and the expensive collateral damaged associated with blowouts.

Not sure of the age of your RV’s tires? All tires are stamped with a four-digit code on the sidewall. This string of letters and numbers begins with “DOT” (Department of Transportation) followed by information about where it was made, tire size and a manufacturer’s code. What you need to find are the last four digits: the first two are the week (52 weeks in a year) and the last two are the year. This tire, on an old trailer in a storage lot, indicates it was built on the 25th week of ’03. It’s well past its prime.

A trailer tire’s size is preceded by the letters, “ST” and may also be accompanied by “For trailer service only.” 205 is the section width in millimeters, 75 is the aspect ratio, which indicates the height or profile of the sidewall relative to the cross-section width, also expressed in millimeters. On this tire, the sidewall is 75% as tall as the cross section is wide. “R” indicates radial and 15 is the rim diameter in inches. Always replace tires with the same size, load rating and tread pattern.

Tires also are stamped with a “max load rating” at a specific inflation pressure. Always take tire-pressure readings when the tire is cold; as they warm up, the internal air pressure increases. Note, too, that maximum tire pressure is the minimum pressure required to handle the load rating of the tire. RV manufacturers provide the tire pressure required on labeling attached to the RV to support the gross vehicle and axle ratings of the chassis. It’s best to have the RV weighed at each wheel when the RV is loaded for a trip and compare the figures with the tables provided by the individual tire manufacturers, but in lieu of that, you should air up tires according to the attached labeling.

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