Home Forums Gear Hunting Trucks and Four-Wheel Drives trailer vs truck tires

To avoid hijacking the thread on age of truck tires...

I ran across this good article on using car or truck tires in place of real trailer tires on trailers. They have some good reasons to avoid using car tires but truck tires with the much stiffer sidewalls are rated for trailers. Car tires flex too much and can cause sway, especially with top heavy trailers like RV's or other enclosed trailers.

Speed would be another issue. Trailer tires are rated for 65 mph with the exception of a couple brands which are rated higher. LT tires can obviously be run at higher speeds. Idaho has an 80 mph speed limit. I wouldn't run any trailer at 80 but limiting yourself to 65 will cause traffic jams and get you run over. 70 is the max truck speed and pulling a trailer at truck speed isn't too bad.

The last part of the article brings up something often overlooked. All wheels aren't equal. You need to make sure the wheel is rated for pressures as high as the tire before you put in the maximum air pressure.

Have you ever weighed your fully loaded RV? Most people haven't. If you don't, anything you do concerning tires or wheels is just a guess and you can be way off. You really should know your trailer's axle weight. Most places with truck scales, like concrete or sand/gravel sales places, will weigh you for a small fee. If you use a bumper pull trailer, I suggest getting a tongue weight while you're there. Knowing it can be very useful sometimes. Pull forward so the truck tires are off the scale and get a trailer axle weight. Then jack up tongue just enough to lift it off the truck hitch and get total trailer weight. The difference between them is the tongue wt.

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Trailer Tires vs. Passenger Vehicle Tires

There are differences in the driving requirements between the tires on your trailer and those on the car or light truck you use to tow it. Therefore, there are distinct differences between the way trailer tires and tow vehicle tires are engineered.

Your tow vehicle is a leader, which means traction is a key focus in the design of its tires. Traction allows your tow vehicle to accelerate down the road, turn around the corner and brake to a stop. Another important consideration is tow vehicle tires are designed for ride comfort, which is achieved in part by allowing their sidewalls to flex.

Your trailer is a follower, which often makes tire sidewall flexing a negative. Sidewall flexing on trailers, especially those with a high center of gravity (enclosed/travel trailers) or that carry heavy loads, is a primary cause of trailer sway. Typical passenger radial tires with flexible sidewalls can accentuate trailer sway problems. The stiffer sidewalls and higher operating pressures common with Special Trailer (ST) designated tires help reduce trailer sway.

"Trailers will be more stable and pull better on tires designed specifically for trailer use. Since Special Trailer (ST) tires are constructed with heavier duty materials, they are tougher than typical passenger vehicle tires."

the full weight rating branded on the sidewalls when used on a trailerAlso consider that Special Trailer (ST), as well as Light Truck (LT) tires are fully rated for trailer applications. This means ST- and LT-sized tires can carry .

However when P-metric or Euro-metric tires are used on a trailer, the load capacity branded on the sidewalls must be reduced by 9%. This means P-metric or Euro-metric tires with a maximum branded load rating of 1,874 lbs. for use on a car is only rated to carry 1,705 lbs. when used on a trailer.

Comparing the load capacities of a pair of tires of the same dimensions fitted to a single axle trailer, ST225/75R15 Load Range C-sized tires inflated to their maximum of 50 psi provide 4,300 lbs. of load capacity, where P225/75R15 Standard Load-sized tires inflated to their maximum of 35 psi would be limited to 3,410 lbs. of load capacity, a total reduction of 890 pounds.

Trailers will be more stable and pull better on tires designed specifically for trailer use. Since Special Trailer (ST) tires are constructed with heavier duty materials, they are tougher than typical passenger vehicle tires. This is a plus because trailer suspension systems are generally stiffer and less sophisticated than automotive suspension systems.

Special Trailer (ST) Tire Speed Ratings
Industry standards dictate tires with the ST designation are speed rated to 65 MPH (104 km/h) under normal inflation and load conditions.

However Goodyear Marathon and Power King Towmax STR tires featuring the ST size designation may be used at speeds between 66 and 75 mph (106 and 121 km/h) by increasing their cold inflation pressure by 10 psi (69 kPa) above the recommended pressure for the rated maximum load.

Do not exceed the wheel's maximum rated pressure. If the maximum pressure for the wheel prohibits the increase of air pressure, then maximum speed must be restricted to 65 mph (104 km/h).

The cold inflation pressure must not exceed 10 psi (69 kPa) beyond the inflation specified for the maximum load of the tire.

Increasing the inflation pressure by 10 psi (69 kPa) does not provide any additional load carrying capacity.

We run truck tires on our gooseneck trailers. There's two flatbeds and a cattle trailer. They all have Firestone transforce HT's. The one flatbed usually runs 20,000+ miles every year, usually fully loaded. The truck tires don't wear out as quick and are less likely to have a blow out. I don't think you can go wrong with them.

I think improper loading of the trailer is more condusive to sway that the tires.
My truck,camper, fully loaded 3 horse slant,bumper pull mule trailer with,fuel, water,tack, hay and me weighs right at 15,000.I was running 16500 with a 20ft goose loaded. No way am I going down the road with all that at 70MPH. Especially with ab BP trailer The truck gets best mileage at65 mph.
Last year coming home from elk hunting,I blew one trailer tire coming down a pass in southern CO. When I replaced it with the spare, I checked another and it was coming apart. I limped into Buena Vista on a Saturday and found a diesel repair shop and the guy had two tires he just got in to put on his trailer. He was nice enough to sell them to me at his cost. Then he mounted an balanced them also.All the other tire shops were closed.

I hadn't had this trailer too long and the tires looked good. Checking the mfg. date though,they were 12 years old. I replaced the other two the next week.

Scariest on my truck though is the Goodyear Duratracks. Soft side walls and they roll going into a bend. They get replaced this fall with Coopers.

The trailer tires get 65 psi in them and the truck gets 75 PSI

Always run your trailer tires at max pressure. 65psi tires get 65. 80psi tires get 80. It is hard to believe how many trailer tires I have killed over the years. Trailer manufacturers use the lightest tire they can get away with. If a better tire/Rim combo will work on your trailer buy them. Buying the firestone transforce LT if they sell them in your size will not be a bad choice. Just bought 5 for the back of my dually. One as a new spare. 225/75/15 load range E trailer tires are not all equal. Carlisle are what I have started to switch out too. After killing a couple sets of off brand

I've doubled the life of my trailer tires by reducing pressure until I need it. Otherwise the centers wear out way too fast, especially on bias tires. Radials are a big help.

I only buy radials.

My 5x8 box trailer (3' high steel sides/plank floor) had P225/15R car tires on it when I bought it about 15 years ago. Hardest-pulling single axle trailer I've ever yanked around.

Replaced them with bias ply trailer tires coupla years ago, pulls like a dream now.

This is a cut and paste from Goodyear Tire:

"Trailer, or "ST", tires are considered a special category in the current global design standards of Tire and Rim. The major difference is that trailer tires are required to carry 10% more load than an equivalent P-metric size tire.

LT type tires are actually on a lower formula and would require a significant size or load change to meet the trailer load requirements.

In the design process, we evaluate what works best under trailer applications/conditions. We typically find that a narrower tread width and a shallower non-skid (tread depth) provides a better overall performance in a free rolling position. This is one case where wider is not better.

There are significant design differences with these tires and this explains why trailer tires are in a special
category. In addition, that is why we recommend using trailer designed or trailer specific tires in trailer towable applications.

Sincerely,

Steve McKay
Consumer Relations
Goodyear Tire and Rubber Company


TRAILER-TIRE CONSTRUCTION
Commonly encountered tires are P (passenger car), LT (light truck) and ST (special trailer). While each tire series shares basic construction methods, such as bias or radial belts, a bead, tread plies and so on, the details vary meaningfully among the three. Considerations in designing tires used on trailers include the need to carry heavy loads, the relative lack of cornering loads, long duty cycles (the tires can be expected to sit for a year; then rotate for days on end during long trips). Furthermore, because the design of most trailer suspensions dates back many decades, ST tires are designed for as soft a ride as possible so they don't transmit too much shock to the trailer and its contents.
Trailer-tire sidewall stiffness is a compromise between P and LT designs. The desire for stiffer sidewalls is still occasionally cited as the reason for choosing a bias-belted trailer tire. While passenger-car tires are nearly all radials these days, ST tires are still available in bias-belted construction. Radial trailer tires are superior in all respects to bias-belted tires except in sidewall stiffness. Reduced tire heat, lower rolling resistance and softer ride are among the benefits of radials, not to mention extended wear. On the road, ST tires share some characteristics of passenger-car tires, but are closer to the design of light-truck tires. Trailer tires typically employ heavier steel or poly-ester cords and somewhat lighter sidewall construction than light-truck
TRAILER-TIRE SAFETY
continued
tires, and trailer tires typically run lower air pressures than their truck counterparts. This gives ST tires good load-carrying capacity; but with the desired softer ride. ST tires also have the advantage of rubber compounds that are specifically designed to resist deterioration from the elements, including sunlight and ozone, during extended storage."

I have found out that make sure you have your trailer tires balanced when you install them,makes a world of difference on how it tows.Installed the E-rated Maxxis ST radial M8008 on my 20 ft PJ trailer(14,000 lbs) fews years back tows great.

Most people never bother to balance trailer tires and I've never figured out why. Bouncing down the road just wears them out faster, not to mention they way they ride.