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Thursday, April 21, 2011

Light Truck tires on trailer

Had a question from a reader
Thanks for your expertise. I am, frankly, baffled about what to do about our tire situation. In this instance, our tire that went flat definitely was not overinflated. It had been checked about two days prior and had 63 pounds. We have been running nitrogen since the tires were put on and have not lost a pound in any of them in 3 months.
When we upgraded to 80 pound, E-rated tires three years ago, I asked about the rims' ability to hold that pressure. Stupidly, I took the tire dealer's word for it.

In 2008, we started blowing Denman tires all over Montana: three of four blew, tires with about 8,000 miles on them.
On our way to Maine in May, we blew yet another tire and sought advice from the guy who owns the campground where we were headed. He is a tire dealer, and advised us to go back to the original equipment 65-pounders, which we did. Now, we have a rim problem.
An 80-pound Maxxis, which we kept as a spare, is now on the trailer. The one that went flat will be on a new rim and used as a spare until we get home. Clearly, we had lost pressure in that tire before we got to the CG; how much is the question. It was not flat or we would have noticed it when we put the chock between the wheels. That tire will undoubtedly go bye-bye when we get home.

I will research rims. It sounds like I should replace all rims with ones that are capable of handling E-rated tires if we want to go that route again. I do not think we have room to upgrade to 16-inch wheels, but I now am going to find out for sure. If it's possible, we will do that.

I am adamant about checking tire pressure, so I am confident we have not been running on over or under inflated tires. We are not overweight, and our axles are fine.

It is obvious we are doing something wrong. I'm beginning to feel like we are too stupid to own this 5er!

Hope your eyes don't glaze over reading all this...thanks for your input.

You didn't mention if you ran 65psi or 80 psi in your "80 pound" tires. I wonder if you are running metal valves, as standard rubber valves are not rated for more than 65 psi. Also the rims have a max load and max inflation rating. Did you check the rim stamping?

You also were not clear if you were running LT or Light Truck tires or had been running ST or Special Trailer tires. These two different type tires have different load ratings even if the rest of the numbers were the same. A LT235/75R16 Load Range E has a different rating than an ST235/75R16 Load Range E.

An "80 pound" Load Range E tire rated for 80psi will carry no more than a Load Range D tire will if they are both inflated to 65psi. It is the air (nitrogen) that does the work and carries the load not the tire. Just because you checked the tire two days earlier is no guaranty you didn't get a nail as you left the CG that day and drove for two days on a leaking tire. This is one of the best arguments in favor of TPMS.

With all the tire failures I have to ask what your real ( not sticker or guess) axle by axle side to side loads are when you are fully loaded going down the road. With those numbers you can consult the manufacturer’s charts.

While you are getting the TT weighed it won't hurt to get the four corner weights of your tow vehicle too.

One thing few realize, including the tire salesman, is that according to Industry Guidelines LT tires require an inflation increase or even a load reduction if you ever drive over 65mph. ST tires also have a speed restriction that needs to be considered. The only way to know if this is not needed is to consult printed literature for your brand and design tire from the tire manufacturer. I would not assume the tire salesperson knows the correct answer.


  1. All of the questions are valid one to consider. The best thing I would do is go ahead and get a set of Goodyear GS614 Tires and make sure the rims will hold the weight. Also, in 2008 they had 8000 miles on them. How Old were the tires? What is the date Code information? 6 year old tires or older and they should not be on the ground in use. It don't matter how old the coach is, CHECK the Date Code on the Tires. Mfg's have been know to get older tires and not notice them.

  2. philton
    Thanks for your comment.
    I will be covering tire age and how to read the date code soon.


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