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Have a 14' light duty trailer, rated for 3000 lbs. Would a set of passenger car tires work well on it? Original ST 205 70 15s are badly checked and I have a chance to buy two car radials pretty cheap.

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.

for comparison
ST 225 x 75R 8PR
load cap 2540
psi 65
OD 28.3

I’ve run 14” car tires on my 12’ utility trailer for years. I’m not hauling a backhoe or skid steer on it.

Tons of folks in here will tell you no problem, but I personally stick to ST tires for the above reason. Any old tire will work pulling a trailer around on the farm, but for serious loads, speeds, and miles, I use the best ST rated tires I can find.

Despite my aversion to Goodyear tires in general, Goodyear Endurance (not marathon) are an excellent ST tire, typically rated above the equivalent sized China bomb trailer tires in load rating. More importantly, they are speed rated N, which is up to 87 mph.

Most China bombs are rated to J, which is only 62 mph. So towing past 62 exceeds their speed ratings. When is the last time you took a drive at less than 62 mph on the highway?

In addition, P-metric and LT tires in trailer applications usually have a lot more sidewall flex.

TL/DR: stick with a N speed rated ST tire that meets your load requirements if you plan on towing at highway speeds.

ETA: run them at maximum sidewall pressure. The Goodyear wins here again, with max psi typically higher than the Chinese tires in an equivalent size.

Thanks all. Think I'll spring for a set of STs

There's a long ongoing argument about whether LT's are good on trailers. They're certainly better than P's. The sidewall markings will tell you how much of a load they can carry. The usual issue is the stiffness in the sidewalls. But there's another issue that doesn't come up very often - durability. ST tires are made to last about 5 years. They recommend that they be trashed after that regardless of tread depth as they dry rot. LT's are good for twice that long - 10 years. From what I've read, ST's don't carry passengers so they can get away with lower grade materials that don't hold up as well for the long run. LT"s do carry passengers so they're made from better rubber that doesn't deteriorate nearly as fast. So, if LT's will carry your load ok, they'll last twice as long for about the same money.

Basscat Boats known for making quality products, including their own trailers, only uses car tires - specifically the General Altimax. They do a lot of research too. The folks at BCB said to only load them up to 90% of the max load and you will never have a problem. Their ressearch shows these tires ride better than straight trailer tires. I have had several of these boats and trailer them all around the country without an issue.

If you want to stick with STs, the Goodyear Endurance is as good as it gets.

Om my open car hauler I use ST 15" tires. On my 16" tandem axle lighter trailer I have used car radials (14") for 15 years without issues. It rarely sees a load of 3000lb, usually 2k or less. I use it to haul my side by side and my zero turn mower (Sometimes together). Car tires are generally more uniform, balance better and if you're within their rated load capacity, I don't see a problem with them.

I had a 9yr old boat-trailer tire come completely apart last spring @ highway speed. Minor damage to the fender, no damage to the boat, the rest of the trailer, or lighting. The spare is roughly the same age but 0 road-time. So, I put on the spare and get where I'm going easy enough. Now it's time to shop for 2 new tires in June, the height of our trailer-pulling season. Availability was spotty if I wanted anything without waiting a month or more.

Short answer, the local trailer shop had several "pairs" of wheels/tires that were supposed to be sets of 4. I got 6 hole 15" AL wheels with new ST 205/75r15 80MPH rated tires on them for $500. Might be worth a stop @ the local trailer store to see what they've got for broken sets etc.

Nope

Run anything except made in CHINA

Decided to buy a new set of STs....not made in China!

I had 2 brand new Goodyear marathon ST tires lose the tread cap doing a tow of 75ish miles round trip. Lost one going up to Elk camp that took out all the plumbing under the TT. Tire never went flat just lost all the tread. The second was coming back home, this one blew out. I put the still inflated treadless tire on and limped home the last 4-5 miles.

I have a deep distrust of any radial tire on a trailer. I have been replacing them with bias ply and have not had a trailer tire failure in years.

Good old 7.50-15s or 7.50-16s 5 pounds under max inflation and i am a happy guy.

I have no problem on either of my single axel utility trailers but will use STs on my travel trailer. The only failure I've had were overaged tires that i should not have been running on. Heat was definitely a factor as it was 108 degrees out when I lost tread in 2 tires but they didn't lose air. I think the first went and that transferred the load to the other and that was it.

When I was in the North country when the tires came off my 4x4 they went on my tandem axel 3 cord log trailer, even took it to CO for a year of cutting posts and poles.