The following were downloaded off the internet at various tire manufacturer & tire manufacturer rep websites....
The load range or ply rating branded on a tire's sidewall helps identify its strength and ability to contain air pressure. While specific load ranges are assigned to passenger tires, load ranges are identified in ascending alphabetical order for light truck tires (the further along the letter is in the alphabet, the stronger the tire and the greater amount of air pressure it can withstand and load it can carry). Before load ranges were adopted, ply ratings were used to identify the relative strength of light truck tires with higher numerical values assigned to tires featuring stronger, heavier duty constructions.
Today's load range/ply ratings do not count the actual number of body ply layers found inside the tire, but indicate an equivalent strength based on early bias ply tires. Most radial passenger tires have one or two body plies, and light truck tires, even those with heavy duty ratings (10-, 12- or 14-ply rated), actually have only two or three fabric body plies, or one steel ply.
And....
From Discount Tires' website:
@
http://www.discounttire.com/dtcs/inf...ionAnxiety.dos
Long-term fatigue can also weaken a trailer tire. There are a number of factors that accelerate fatigue, but heat buildup from towing at high speeds is one of the main culprits, according to Fry.
"If you trailer nonstop from Phoenix, Arizona, to Las Vegas, in 100-degree temperatures at 65 mph, you use up much of the resources of that tire, and you don't realize it," said Fry.
Fry is not talking about wearing out the tread. It is the tire's construction that is breaking down. As heat builds up, the tire's structure starts to disintegrate and weaken. Over the course of several trips, this load-carrying capacity gradually decreases, according to Fry. Incidentally, all ST tires have a maximum speed rating of 65 mph.
One key to extending tire life on a tandem- or tri-axle trailer is to ensure that the trailer is riding level, thus distributing the load equally among all the tires. If the trailer tongue sits too high, the rear tires may bear the brunt of the load: with the trailer tongue too low, the front tires may be unduly stressed.
THIS statement sums up my personal belief as I do not tow at high speeds:
While radials were frowned upon at one time, today there is wide-spread acceptance of these tires. Which should you use? The decision hinges on your towing style, according to Ray Evans, executive vice president for engineering, marketing and sales of Titan Tire Corp. in Mogadore, Ohio. "While it is true that a bias-ply tire can provide more side-to-side stability than a radial, a bias ply also runs hotter than a radial," said Evans. "If you are pulling a heavy load, and need an extra measure of stability, use a bias ply."
To each his own
Having towed over 100,000 miles w/ no incident, I will continue to use "E'" rated bias ply trailer tires on single axle travel trailers over 3500 pounds and all tandem axle trailers.....
No offense, but I believe other quality concerns with vintage Airstream engineering will cause failure before increasing the tire rating from "D" to "E"
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