QuestionQUESTION: What is the difference between truck tire and trailer tire? I have 32 ft trailer with two 5200 lb axles and 10 ply 15 inch tires and not overloaded running 65 lbs psi. The tires start separating and blowing out in about 23 months. The 8 ply tire did the same thing. I would like to use Firestone Transport 16 inch 10 ply truck tires on the trailer as they seem to have no problems on a E350 Ford van loaded heaver than the trailer. The trailer tire still have good tread and only about 20,000 miles. Have tried different brand tires and all do the same thing.
Thanks Phillip
ANSWER: Phillip,
Part of the problem is that inflation pressure has a large effect on load carrying capacity. So when you went from Load Range D to Load Range E (I don't like to use the "PLY" term since it promotes confusion.), in order to get more load carrying capacity, you also needed to use more inflation pressure.
I think your first step ought to be to weigh the trailer in its worst case - fully loaded, all wtaer tanks full - white, gray and black - and tire by tire if possible, but certainly axle by axle. Then figure out what reserve capacity you have in your tires. I think 15% is OK, but 20% would be better.
I don't think load carrying capacity is 100% the problem with trailers. Part of it is the suspension, which is not as soft as a truck, and therefore more force is absorbed by the tires. This is why I use 15% and 20% reserve capacity to account for this.
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QUESTION: you did not answer my question = what is the difference between truck and trailer tires.
ANSWER: Phillip,
The reason I didn't answer the first question that you asked was that I thought you were more interested in solving your problem rather than getting a technical explanation of the differences.
There is also the issue of what you mean by "truck tire" vs. "trailer tire". For the purposes of this discussion, I am going to assume "truck tire" means "LT metric" and "trailer tire" means "ST tires". These are designations that define the relationship between maximum load carrying capacity vs inflation pressure.
The best information I have says there is no structural difference between LT metric tires and ST tires - except to say that an LT metric tire will likely be designed with a little wider tread (and therefore belt package) for handling purposes. The major difference seems to be the amount of load each is allowed to carry.
Put a different way, the load carrying capacity of an ST tire is 20% greater than an LT tire. Since durability is strictly a long term issue - and the results of a tire failure on a trailer are much less life threatening than on a truck - the folks that set up these load / inflation pressure relationships allow a greater......ah......let's call it load intensity.
The other part of this is that ST tires generally don't have to deal with large cornering forces - and these forces were hard to quanitify when the category was established many, many years ago. These forces have a profound effect on durability.
But I still think that you need to weigh everything to establish where you are. I keep hearing of many trailers that are - oh, let's say marginal, when it comes to tire sizing. As a result, I think repeated failures should prompt folks to get back to basics.
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QUESTION: Thanks for the info, that is what I was wanting. If I read you correct a load range E trailer tire is rated more than a E rated truck tire just as a safety factor. The truck tire in theory should be better because of width in handling. As I see it a load range E truck tire could possibly be better or at least as good on a trailer but a trailer tire would not be safe on a truck because of its construction. ST 225/75R15 E with 2830 lb is the largest 15 in tire I can find. A LT 225/75R16 E with 2680 lb is a larger and taller which means less revolutions/less heat than the 15. With the added 20% to make it as a ST the cap would be 3216 or 386 lb more than the ST. That would be 1544 lb more on a 2 axle trailer.
The trailer I have is 32ft cargo with GVW of 8000 to 10,000 lbs with two 5200 lb axles. The 2830 lbs of the 15s x 4 = 11,320. That puts me at max around 50% of the time with the 15% factor you mentioned.. The 16s should help with the seperation problem.
AnswerPhillip,
Not exactly. An LT metric tire should not have any real advatantage when used in place of an ST tire. And an ST tire shouldn't be used on a truck because of handling deficiencies that will be inherent in the design, since a trailer doesn't have any real neeed for handling properties.
".....A LT 225/75R16 E with 2680 lb is a larger and taller which means less revolutions/less heat than the 15...."
This really isn't significant so don't use this bit of logic to make a decision.
Clearly a larger tire would be helpful. But at the same time, you need to be sure of the weight you are trying to carry. I would hate it if you went though all this and discovered that you didn't go far enough.
