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Old 07-11-2007, 05:18 PM   #15
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I would like to offer, as food for thought, that "failure due to underinflation" does not mean, IMHO, inflation at less than the maximum inflation stamped on the tire. If the chart for my tires shows that, based on the scale weight, the correct inflation should be 55 psi, then I would not be underinflated unless I chose to run the tires at less than 55 psi. If I ran the tire at 60 psi, and the maximum psi allowed was 65 psi, I would, by no means be "underinflated." This does not change, or cause me to question, the statement that "---most tire failures are due to underinflation."
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Old 07-11-2007, 05:33 PM   #16
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Originally Posted by millvalleyca
Now I'm back where I started!
45 and not 65 as stated on the tire HowieE?
80% inflated doesn't seem that bad then.
I was going to go out and buy an air compressor tonight to fill up my tires.
Now I'm gonna have to read a couple of more suggestions
It sure is tough when you're a newbie who knows nothing about cars/trucks and trailers.
Thanks for the info
Sorry if I left you in confused state.

What I failed to mention in my last post is the fact that in order to have your tires properly inflated you have to know the weight of the trailer as you are using it. This may differ significantly from the Manufactures sticker depending on how you have loaded it. In order to know the weight you have to have the trailer weighed, this can be done at any truck stop.

Once you have this information go to your tire manufactures web site and look at the inflation chart for you tire and weight.

I know several have posted that I am off base with this position but I trust after you look at a manufactures chart you will agree with what I have posted. Remember those tire companies have large engineer staffs and even larger legal departments and they would not publish this information if they did not have faith in it.

By the way the sticker on my truck calls for a tire pressure of 80 lbs. but with the scale weight the front axle is set at 45 lbs and the rear at 55lbs
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Old 07-11-2007, 05:40 PM   #17
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Quote:
Originally Posted by Cracker
I would like to offer, as food for thought, that "failure due to under inflation" does not mean, IMHO, inflation at less than the maximum inflation stamped on the tire. If the chart for my tires shows that, based on the scale weight, the correct inflation should be 55 psi, then I would not be under inflated unless I chose to run the tires at less than 55 psi. If I ran the tire at 60 psi, and the maximum psi allowed was 65 psi, I would, by no means be "under inflated." This does not change, or cause me to question, the statement that "---most tire failures are due to under inflation."
You are correct to a point. If you know your trailer's weight you can determine the proper inflation pressures to carry that weight. The unknown factor is speed and the faster the tire turns the more the weight capacity is reduced.

Consider the fact that with a tandem axle Airstream, you are advised that you can tow with one of the tires removed.....but also note they give you a maximum speed of 45 mph. Why? Well one reason is a control issue, the other is that the remaining tire has the ability to carry the additional load at reduced speeds.

The problem with the "good old boy advice" that you can tow at 80% pressure when unloaded may or may not be true. I'll bet you an Airstream that if you pulled away and blew a tire that that dealer would not stand behind that 80% statement. They probably would deny even making that statement.

It may be valid for your particular trailer if you know the weight and speed you are towing at and how that relates to the tire's load capacity. But if you are like most of us, you don't have a scale at home and you probably can't get to a roadside scale with cold tires. My feeling is why guess? I'll fill 'em to 65 and if they blow, at least I'll know it wasn't due to my inattention to tire pressure.

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Old 07-11-2007, 07:11 PM   #18
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I want to correct an error I made in Post #14 when I said the original tires on my Excella were Load Range "D" and I switched to Load Range "E." In truth, the original tires were Load Range "C" and I switched to Load Range "D." The maximum inflation pressure for the C's was 50 psi - which is exactly what Airstream recommended - and what the capacity of the trailer is based on - i.e. - 4,000 lbs/axle, or 8,300 lbs net. When I switched to the D's I continued to use the 50 psi recommendation since the load capacity for either rated tire is the same at 50 psi - and I know by actual scale weight that the net load on the pair of axles is 7,400 lbs when loaded for the road and properly hitched to the truck. Incidentally, my hitch weight, using a Sherline scale is 900 lbs, for a total load of 8,300 lbs, or exactly the design rating of the trailer.

As for the truck, the scale weight for the rear axle is 4,900 lbs, or 1,225 lbs per tire if evenly divided. I gave the inflation values I use previously. If I ran the rear load range "E" tires up to their maximum 80 psi, two tires would carry my present loaded weight - however, even at that pressure those two tires would not carry the rear axle design load of the GMC dually. In other words, if one of the dual tires blow out with a full load (---as specified by GMC) the remaining tire will not carry the load at normal highway speeds. I'm trusting, that GM has calculated that there is enough safety factor in the tire capacity to allow me to slow down and stop - or limp to the nearest tire center.

Whew! Excuse all the long-winded explanation - and pity my wife! She's all-too-often my only ear.
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Old 07-11-2007, 09:01 PM   #19
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When we bought our 23 we noticed it had P rated 235 X 75 X 15 Michelin Tires branded as a Sears. I took one to Sears for an opinion. Apparently they were over 12 years old and look fairly good. The PO towed a lot.

We all know the story about how a P rated tire can be forced off the rim by performing a tight, slow turn. Just wondering..... True or False?? Has anyone acually had or heard of a P rated tire falling off a rim?

When you think about it a P rated tire could be perfect for a Vintage Airstream. The 35lb pressure is nice and the larger footprint would increase stopping distances. More rubber contact on the road.

P rated tires in most cases are reliable compared with the problematic ST tires.
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Old 07-12-2007, 09:49 AM   #20
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Quote:
Originally Posted by Cracker
- however, even at that pressure those two tires would not carry the rear axle design load of the GMC dually. In other words, if one of the dual tires blow out with a full load (---as specified by GMC) the remaining tire will not carry the load at normal highway speeds. I'm trusting, that GM has calculated that there is enough safety factor in the tire capacity to allow me to slow down and stop - or limp to the nearest tire center.
Interestingly enough I learned at a tire safety seminar that I attended, most people don't realize that the weight capacity of the tires mounted in a dually configuration is less than twice the rating of the two individual tires. Apparently the inside tire always runs hotter. I have a tire inflation chart for Michelin RV tires used on motor homes that has a qualifying column that shows the reduced capacity of a tire when it is used on the inside wheel of a dually configuration.

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Old 07-12-2007, 12:51 PM   #21
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Does anybody know how hot is too hot for the tire temperature? While I was stopped for lunch last week and measuring the temperature of the sidewalls of my trailer's tires, another RV'er (motorhome) asked me what range was I looking for. I told him, truthfully, I wasn't sure but I thought if the temperature seemed too outrageously hot I kind of recognize it. I know the blow-out temperature for semi tires is about 300F from a recent episode of Mythbusters. At what temperature should I get concerned?
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Old 07-12-2007, 01:15 PM   #22
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Now I have to go out and buy an infared thermometer to measure the temp of my tires?!
One more thing to worry about?
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Old 07-12-2007, 02:02 PM   #23
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Quote:
Originally Posted by millvalleyca
Now I have to go out and buy an infared thermometer to measure the temp of my tires?!
One more thing to worry about?
Keep checking back and we, your faithful peanut gallery, will have your mind awash with techno fodder!

As covered above, download the pressure/weight chart for your trailers and TV's tires. Check your weight and inflate accordingly using the method recommended by the manufacturer (cold, correct?). I bought an infared thermometer to play with. The laser drives the cat crazy.

BTW, my TV's tires are max rated at 80 PSI but the fully loaded correct pressure, while towing, is 55 psi. Quite a difference, huh?
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Old 07-12-2007, 02:06 PM   #24
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Tire Pressure

millvalleyca
If you have the ST tire other than the Cooper Custom Trailer Plus, run them at max pressure. This minimizes the sidewall flex and hense the heat build up in the tires. More importantly slow down.
Slowing down will also slow the heat geneeration.
Slow down how much? I dont know.
My tires are speed rated to 99 MPH. At 65 I have a 34% safety margin.
To attain that same safety margin you would have to do 43 MPH with the ST tire(except for the Cooper Custom Trailer plus).

I see a number of failures on the forum but somehow they don't seem to be turning up on the National Highway Transportation Safety Administration web site.
If you have a tire failure report it at this web site:

IVOQ - File a Complaint

Do us all some good.
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Old 07-12-2007, 02:36 PM   #25
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Minnie's Mate,
There was a recent post regarding the IR/laser temp gauges (available at Harbor Freight) that I think had the temperature ranges. I'll search for it.
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Old 07-12-2007, 02:47 PM   #26
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Does anybody know how hot is too hot for the tire temperature?
I carry a Radio Shack infar red thermomator more for checking bearing temperature than tires. As for tires, just after I pull into a rest area I touch each sidewall of the tires. If I can hold the tire I am happy. Those that I have measured witht he thermomator generaly ru about 110 degrees F. Keep in mind that if you are traveling across the sun the tires on the sunny side will be about 10 degrees hotter than the shady side. Just a fact of nature.

If you touch a tire that has ply seperation and is about to go you will know it by the touch.

If I want to test the bearings I will coast into the rest area without using the trailer brakes. Having done that and if I find a Hot Hub I know I either have a bearing problem or a dragging brake.
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Old 07-12-2007, 02:53 PM   #27
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OK....I printed the inflation chart that HowieE made available.
How do I read it?
Find my tire size on the chart.
Single (S) or Dual (D)...I have four tires so the "Dual"?
The lbs represent per tire weight??? Times the number by four?
Does anyone have an "etimate" as to how much my trailer might weigh?
We have the regular stuff in the trailer for 2 adults and 2 kids. Nothing overly heavy and not filled to the brim.
Thanks AGAIN!
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Old 07-12-2007, 02:56 PM   #28
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I have never NOT been able to hold my hand on the side walls of my tires. When I used my infrared thermometer on this last trip I found, as you say, a 10F difference between the sunny side and the shaded side of the trailer. I figured since the temps were lower than the tow vehicle's tire temps and way below the 300F that the Mythbusters show said was the blow-out temp for semi tires (I know, big difference between an Airstream and semi), that I was probably OK. But I'm just curious, at what point should I start to worry?
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