| SERRO SCOTTY CAMPER ENTHUSIASTS ST TIRES OR RADIALS? |
The "ST" Sign
Look at the sidewalls of the tires on your car or truck you'll will see a "P" or "LT" designation. P stands for
"passenger" while LT indicates "light truck," These indicate that that tire is designed for automotive/truck use. The
marking on your trailer tire sidewall, will be an "ST" designation, which stands for "special trailer."
ST tires have been specifically designed for use on trailers and they are considerably different from automotive tires.
The ST tire has inherent benefits specific to use on a trailer.
1. An ST tire has about 10 percent more load capacity than an equivalent LT tire and nearly 40 percent more than a
P tire when each is filled to its maximum psi rating.
2. An ST tires's mold shape is designed to accommodate trailer wheels, which are typically narrower than P and LT
wheels.
3. Because ST tires are narrow they roll easier. A free-rolling trailer tire does not need to turn or grip pavement like
a steering or drive tire.
4. ST tires don't need a deep of a non-skid tread as P and LT tires do. As a free rolling, tire a deep gripping tread
would be detrimental to its performance. Having a shallower tread depth provides the ST tire with two benefits:
a. it doesn't wiggle as much, which can help reduce sway.
b. it rides cooler, which adds to its longevity.
A ST tire also has stiffer sidewalls to reduce sidewall flexing. That will help prevent sway. The stiffer sides also lessen
the risk of sidewall blowout.
Bottom line. Don’t put passenger or light truck tires on a trailer.
Under-Inflation
The most common cause of tire problems is under-inflation. It is estimated that a trailer tire that is 20 percent under-
inflated will cut 25 percent off its lifespan; one 30 percent under-inflated will reduce its term by 55 percent. Under-
inflated tires also affect fuel efficiency by as much as 10 percent due to added drag.
More important, under-inflation puts undue stress on the tire, producing irregular wear at best. At worst, under-
inflation causes complete failure that can result in an accident. Abnormal tire flexing occurs when a tire doesn't have
enough air, which can generate an excessive amount of heat internally. Too much heat will exceed the tire's
capabilities and cause the tire plies to separate or result in a blowout.
Merely looking at a tire won't always tell you if it is under-inflated. In fact, some tires can lose up to half of their
pressure before it is noticeable from appearance alone. (But you still should check for cracks or other signs of wear.)
And with each pound of pressure loss, there is a corresponding loss of load-carrying ability. Therefore, you should
check the tire's pressure regularly with a good quality gauge. And for accuracy, always check the pressure when the
tire is cold. Driving only a few miles will heat the tire and increase the pressure reading.
Overload
Another major cause of tire failure is overloading. That is why it is important to know the actual load being towed. That
includes the boat, trailer and any gear, including the boat fuel in the boat. An overloaded tire will produce an
inordinate amount of heat, which, as mentioned above, can cause tire degradation or blowout.
So make sure to give your trailer tires a bit of attention. You'll find that taking good care of them before a long tow will
make for a whole lot more trouble-free miles.
Look at the sidewalls of the tires on your car or truck you'll will see a "P" or "LT" designation. P stands for
"passenger" while LT indicates "light truck," These indicate that that tire is designed for automotive/truck use. The
marking on your trailer tire sidewall, will be an "ST" designation, which stands for "special trailer."
ST tires have been specifically designed for use on trailers and they are considerably different from automotive tires.
The ST tire has inherent benefits specific to use on a trailer.
1. An ST tire has about 10 percent more load capacity than an equivalent LT tire and nearly 40 percent more than a
P tire when each is filled to its maximum psi rating.
2. An ST tires's mold shape is designed to accommodate trailer wheels, which are typically narrower than P and LT
wheels.
3. Because ST tires are narrow they roll easier. A free-rolling trailer tire does not need to turn or grip pavement like
a steering or drive tire.
4. ST tires don't need a deep of a non-skid tread as P and LT tires do. As a free rolling, tire a deep gripping tread
would be detrimental to its performance. Having a shallower tread depth provides the ST tire with two benefits:
a. it doesn't wiggle as much, which can help reduce sway.
b. it rides cooler, which adds to its longevity.
A ST tire also has stiffer sidewalls to reduce sidewall flexing. That will help prevent sway. The stiffer sides also lessen
the risk of sidewall blowout.
Bottom line. Don’t put passenger or light truck tires on a trailer.
Under-Inflation
The most common cause of tire problems is under-inflation. It is estimated that a trailer tire that is 20 percent under-
inflated will cut 25 percent off its lifespan; one 30 percent under-inflated will reduce its term by 55 percent. Under-
inflated tires also affect fuel efficiency by as much as 10 percent due to added drag.
More important, under-inflation puts undue stress on the tire, producing irregular wear at best. At worst, under-
inflation causes complete failure that can result in an accident. Abnormal tire flexing occurs when a tire doesn't have
enough air, which can generate an excessive amount of heat internally. Too much heat will exceed the tire's
capabilities and cause the tire plies to separate or result in a blowout.
Merely looking at a tire won't always tell you if it is under-inflated. In fact, some tires can lose up to half of their
pressure before it is noticeable from appearance alone. (But you still should check for cracks or other signs of wear.)
And with each pound of pressure loss, there is a corresponding loss of load-carrying ability. Therefore, you should
check the tire's pressure regularly with a good quality gauge. And for accuracy, always check the pressure when the
tire is cold. Driving only a few miles will heat the tire and increase the pressure reading.
Overload
Another major cause of tire failure is overloading. That is why it is important to know the actual load being towed. That
includes the boat, trailer and any gear, including the boat fuel in the boat. An overloaded tire will produce an
inordinate amount of heat, which, as mentioned above, can cause tire degradation or blowout.
So make sure to give your trailer tires a bit of attention. You'll find that taking good care of them before a long tow will
make for a whole lot more trouble-free miles.
