Replacing tires on the family sedan or tow vehicle is a well-supported endeavor with significant amounts of educational material available. Trailer tires, on the other hand, receive very little attention, but properly buying trailer tires does not need to be difficult or mysterious. Armed with a few bits of information, and a small amount of knowledge, keeping a trailer rolling with a properly fitted set of tires is as easy as hooking up for a long weekend at the lake.

To start the process, it is required to know the maximum loaded weight of the trailer, also known as gross vehicle weight. The safest weight measurement to use is the maximum weight capacity per axle. There will be a plate or sticker attached to the trailer that lists the vehicle identification number, or VIN, as well as the weight rating. This may be listed as gross vehicle weight, GVW, or a maximum load per axle. Sizing tires to this rating will ensure safe function for a properly loaded trailer.

Taking note of the size of the tires that are currently installed on the trailer will also help in this process. Caution should be used, however, if the trailer has been previously owned, since a former owner may have installed tires that are improperly sized. When in doubt, sizing tires base on the VIN plate is always the safest option. The rim size for the tire that is being replaced is also required and can be either measured manually or taken from the size on the existing tires.

With this information in hand, new tires can now be selected for the trailer. Tires are classified according to their intended usage with P rated tires for passenger cars, LT tires for trucks and vans and ST rated tires intended for use on trailers. Only tires with an ST rating should be used on trailers. The materials and physical construction of these tires are specially designed to handle the higher load requirements for trailers. All ST tires are rated at 65 miles per hour so there is no need to designate a speed rating.

There are a few items to keep in mind when finally selecting new tires. First, the combined capacity of all tires on the trailer should exceed the maximum load by at least 20 percent. Second, all tires must also be of the same size. Finally, if larger tires are installed than those being replaced, the axle height might require adjustment to maintain proper balanced of the hitched trailer.

Once new tires have been installed, they should be maintained with utmost care to ensure service throughout the expected lifetime of the tire, which is typically three to five years. Tires at the end of their life span should be replaced regardless of available tread depth. The demands of carrying heavy loads weaken the sidewalls and make old tires prone to failure. Selecting properly sized tires, and keeping them properly inflated, will go a long way to ensuring safe service for a trailer.