ST vs LT tires.

FastEagle wrote:

Here are a 3 facts about the differences in the 2 types of tires.
A ST235/80R16/E Goodyear Marathon is 9.2” wide and 30.7” in diameter on a 6.5” rim. The standard rim width for the tire described above is 6"
A LT235/85R16/E BFG Commercial T/A is 9.3” wide and 31.8” in diameter on a 6.5” rim.

Goodyear lists on their web site that the ST235/80R16/E Goodyear Marathon tire is approved for a 6"-7.5" rim. They also list the 16" tire as being measured on a 6.5" rim

A LT235/85R16/E gives up a little about 10% in load carrying capacity to the ST235/80R16/E.

A LT235/85R16/E has a speed rating about 50% higher than the ST235/80R16/E

Now opinion about the 3 facts above
While the difference in size is minimal, it should not be ignored. But I can’t recall anyone going from 235/80R16 to 235/85R16 having problems. The diameter of the LT235/85R16E is too tall for fitment on trailers with 33" center to center dual axle placements.

A pair of 31.8" tires will fit a 33" axle spacing, and leave a gap greater than 1"

The loss of 10% of the load carrying capacity can be a problem, depends on GAWR. But an F or G range tire such as the G614 would solve that issue. There are not many of them to choose from and they almost always require new rims because of the load capacity and pressure rating needed for their fitment, not to mention the 6.5" minimum rim width requirement.


Agreed

The difference in the speed rating is substantial. Speed makes heat, heat kills. This means that the LT either does not make as much heat, it withstands the heat better, or most likely some of each. If I am running down the road at 63 MPH on ST tires I am right at the limit. With the LT tires I’m only at 66%. This is a big difference.
Speed ratings are based on laboratory tests, but, are not applicable if tires are underinflated, overloaded, worn out, damaged or altered.

Agreed


But since the trailer manufacturer specifies the OME tire, the tire manufactures will not recommend a change of tire size and carrying capacity. Because they did not build the vehicle and there are no other recommendations from the vehicle manufacturer. They will not assume that liability. Likewise many retail chains will not install a tire that is not OEM spec. Like Fast Eagle says, it’s a misapplication.

Agreed


The trailer manufacturer buys a legal tire at low cost. The tire manufacturers sell tires that are made at low cost. We sit on the side of the road with blown tires, or we find a better tire. Even if it does not meet factory specifications. Have you assumed or are you implying a legal tire (as you say) is the cause of the failure? Can there be another explanation for the "blown tire"?

The opinion is that a tire that is marginal at best (certified only for trailer use and at reduced speed), made in a country that is known for poor quality control is a bad risk. Add to this users that do not understand the design limitations, they speed, do not check air pressures. Plus the just plain bad luck of curbs, pot holes, and trash in the roadway. All add up to tire failures. The key is to eliminate or reduce as many of the risk factors as possible.



Here are a few observations in red.

FastEagle