Trailer tires should carry an ST (special trailer) marking, not a passenger or light-truck one, because they are built to hold weight straight down with stiff sidewalls rather than to steer. Milwaukee Tire Shop in Milwaukee, WI can read the load range and date code on your current trailer tires and help match replacements.
Trailer tires usually fail from age and load long before the tread wears out. A boat trailer that sits all summer with weight on the rubber, or a utility trailer parked beside a garage through a Wisconsin winter, can show cracked sidewalls on tread that still looks new.
Start by reading the sidewall. The letters ST mean it is a trailer tire, the load range letter tells you what each tire is rated to carry, and the date code tells you when it was made. Have that information, or a photo of it, ready when you call Milwaukee Tire Shop.
Can I put regular car or truck tires on a trailer?
People do, but it is the wrong tool. A passenger tire has a softer sidewall tuned for steering and ride comfort. A trailer tire never steers. Its job is to carry load and resist sway, so the sidewall is stiff and the rubber is built for constant weight. A softer tire under a loaded trailer flexes and heats up, and the trailer can start to wander at highway speed.
On a tandem axle, keep all the tires the same size and type. A mismatch makes one tire carry more than its share.
How can I tell the tires are too old when the tread still looks good?
Go by the date code and the sidewall, not the tread. The code is four digits, giving the week and year of manufacture. Fine cracks in the sidewall or between the tread blocks mean the rubber has dried out, and a flat spot from long storage can leave a thump you feel in the tongue.
A trailer that lives outside ages faster on the side facing the sun. Covers help, and so does moving the trailer now and then so the weight is not always resting on the same patch.
Why is only one edge of the tire wearing out?
Wear on a single edge points to the axle or the suspension, not the tire. A bent axle or a worn spring hanger tilts the wheel. Replacing the tire without finding the cause means the new one wears out the same way.
What does ST mean on a trailer tire?
ST stands for special trailer. These tires are built for load and sway resistance instead of steering. Check the load range letter next to it, since that sets how much each tire may carry.
Should I replace all the trailer tires at once?
Replace them in pairs at minimum, and match every tire on the same axle. If the date codes show the whole set is old, replacing all of them is the cleaner fix. Bring the codes when you call.
Do I need a spare for my trailer?
A spare is worth carrying, because a trailer blowout leaves you stuck on the shoulder with no way to limp to a shop. Make sure the spare matches the size and load range of the others, and check its date code too.