There has always been confusion when it comes to the type of tires used on travel trailers and 5th wheel trailers, or any type trailer for that matter. I think lots of folks are somewhat familiar with what are referred to as P-rated (passenger) or LT-rated (Light Truck) tire designations because that is what we use on our automobiles, SUVs and trucks. When you purchase a travel trailer or 5th wheel trailer and the time comes to buy new tires people are confronted with a new type of tire designation, ST-rated or Special Trailer tires.
Before we get into what “ST” tires are I want to talk briefly about some misinformation concerning ST trailer tires. Trailer tires get a bad rap in general for several reasons. In many cases the reason for tire failure on a trailer is due to overloading the tire, improper tire inflation, the age of a tire or constant exposure to the elements. I can’t tell you how many times I hear stories about tires with only 10,000 miles and plenty of tread failing for no reason. What people fail to mention is the tires are 7 or 8 years-old, have cracks in the sidewalls, and are exposed to the sun and elements every day. In other cases some fail to mention a tire was overloaded by 300 or 400 pounds and the tire failure happened while towing the trailer in 90 degree temperatures. I am not saying this is always the case or reason for trailer tire failure, but it is in many situations.
With that said the designation ST stands for Special Trailer tire. ST tires are designed specifically for use on trailer axle positions only. They are not designed for the load or traction requirements of a drive or steering axle. ST tires have strengthened sidewalls to help prevent the tire from rolling under the rim in turns and when cornering. The majority of ST tires have a maximum speed rating of 65 mph. ST tires feature materials and construction designed to meet the higher load requirements and demands trailer towing places on a tire.
There has always been controversy surrounding whether to replace ST tires with a good quality LT tire. There are some LT tires I think would do the job on a trailer, but at the end of the day if ST tires are properly matched for the application, properly inflated, maintained and not overloaded they are the right tire for the job, in my opinion.