RV and Trailer Tires: Age, Load and Storage

A car's tires are driven almost every day. They flex, warm up and wear down, and they usually reach the end of their tread long before age becomes a problem.

A travel trailer, a fifth wheel, a motorhome, a boat trailer or a utility trailer lives a different life. It may cover a few thousand miles a year, all in a handful of trips, and sit still for the rest. The tread can look nearly new while the rubber underneath has aged, dried and lost strength.

Nobody is sitting on a trailer tire either. A problem a driver would feel through the steering wheel of a car goes unnoticed behind the hitch until the tire fails outright. The trailer tires page calls them the most neglected tires on any vehicle, and that is the reason.

Every tire carries a date code on the sidewall. Look for the letters DOT followed by a string of characters. The last four digits give the week and year the tire was made: a code ending in 2219, for example, means the 22nd week of 2019.

The code may be on one side of the tire only, so check the inside face if you cannot find it.

There is no single age at which every tire must come off. Tire and vehicle manufacturers publish their own guidance, and the RV or trailer manufacturer's handbook may add its own. Find the figure that applies to your tires and treat it as a limit, not a target. When the tires are getting close to it, plan the replacement before the season rather than during a trip.

Signs that age has already done damage:

• Fine cracks in the sidewall or between the tread blocks.
• A dry, faded or chalky look to the rubber.
• Bulges or bumps anywhere on the tire.
• Tread separating at the edges.

Any of those is a reason to replace the tire regardless of the tread left on it.

An RV or trailer tire carries weight continuously, and the load rating on the sidewall must cover what it carries. Trailers are often loaded more heavily than their owners realize, and a tire running near or over its rated load builds heat, which is what breaks a tire down from the inside.

Weigh the loaded rig if you can, axle by axle. A public scale is the usual way to do it. Then compare the weight on each axle with the combined rating of the tires on it, and leave a margin.

Two points that catch people out:

• Trailer tires and passenger tires are built differently. Tires made specifically for trailers are designed to carry load and resist sway, and they are not interchangeable with passenger car tires. Replace like with like unless the trailer manufacturer says otherwise.
• Pressure decides capacity. A tire only carries its rated load at the pressure printed on the sidewall or in the manufacturer's tables. Run it low and its real capacity drops.

Check pressure before every trip, cold, before the rig has moved. A tire checked after an hour on the highway reads higher than it really is, and letting air out of a hot tire leaves it underinflated once it cools.

Use the pressure set by the RV or trailer manufacturer, usually on a placard near the entry door or on the tongue, or the figure in the tire manufacturer's load tables for the weight you actually carry. The tire pressure check guide covers where the correct number is printed and why cold readings matter.

How a trailer is parked between trips does more to its tires than the trips do.

• Keep the sun off them. Ultraviolet light ages rubber. Tire covers on a trailer parked outdoors are cheap protection.
• Get them off bare ground. A board or mat under each tire keeps moisture and chemicals away from the tread.
• Take the weight off for long storage where you can. Leveling jacks or stands reduce the load the tires carry for months at a time.
• Keep them away from ozone sources. Electric motors, generators and welders produce ozone, which cracks rubber.
• Keep them inflated. A tire left low for months takes a set and can be damaged before it ever rolls.
• Move the rig occasionally. Rolling it a short distance shifts the part of each tire carrying the load.

• Read the date code on every tire, including the spare.
• Look over each sidewall and the tread for cracks, bulges and separation.
• Set pressures cold to the correct figure.
• Check the lug nuts are tight.
• Look at the wheel bearings' service history. A dry or worn bearing produces heat that ends tires quickly.
• Check the spare actually holds air. It is usually the oldest tire on the rig.

A trailer with axles out of line drags its tires sideways, and the wear shows on the inner or outer edges. A bent axle, worn suspension parts, or a hard hit against a curb can all cause it. Trailer alignment covers the measurement for trailers that need it, and the tow vehicle's tires are worth checking at the same time. The all-terrain tires guide covers choosing tires for the pickup at the front of the rig.