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Old 07-03-2013, 10:49 AM   #491
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Originally Posted by pappy19 View Post
You've got to figure that the ST tire folks know that even if they do have a problem, it's not a "life threatening" situation, since their tires are on a trailer that's not supposed to have a human inside. They have "no worries" if it's only a matter of a little mechanical/body damage due to a flaw in their product. The LT tires on the other hand, demand a much higher QC or big law suits will follow. Stands to reason the LT's, even if more money to start, are a better investment in the long run, not to mention the safety factor.
Plus and further to my last post on this subject: who of us is equipped to mount a case that shows the tire blow out was a tire defect. To do that we would have to have a laboratory test facility mounted in the TT monitoring all the tires all the time for the life since new...Not going to happen. So this allows them to make a sub spec product that no one will ever prove anything to support that allegation.
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Old 07-04-2013, 04:05 AM   #492
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Great post, please tell us more.

Is there a delamination temperature threshold as a rule of thumb or does it vary with tire design/construction?

I haven't been out on the road with my IR as yet and previously could only estimate temp by feel which appeared to be slightly above body temp.

Perhaps those that have IRs and monitors could keep a log of what they experience on the road.

Your post brings up areas I had not considered.

Again please tell us more or can you recommend a website that would cover such? Again many thanks.
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Old 07-04-2013, 07:09 AM   #493
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Great post, please tell us more.

Is there a delamination temperature threshold as a rule of thumb or does it vary with tire design/construction?

I haven't been out on the road with my IR as yet and previously could only estimate temp by feel which appeared to be slightly above body temp.

Perhaps those that have IRs and monitors could keep a log of what they experience on the road.

Your post brings up areas I had not considered.

Again please tell us more or can you recommend a website that would cover such? Again many thanks.
Here's a rule of thumb:

If the pressure buildup inside the tire is 10% or less, then the running temperature of the tire is OK.

If the pressure buildup is between 10% and 15%, some action needs to be considered. That action could be more inflation pressure, less load on the tires, a larger tire size, etc.

If the pressure buildup is 15% or more, then action needs TAKEN. This is too much and the internal running temperature will be too high. Something MUST be done to lower the pressure buildup and therefore the running temperature of the tire.

So how does that relate to an Infrared thermometer reading on the tread surface? I don't know, but I'll bet a few correlation readings from folks who have such devices will help sort this out.

I'll bet, though, that the correlation isn't very good and varies quite a bit.
I'll also bet the best that can be done is to have a maximum temperature buildup and a maximum temperature.
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Old 07-04-2013, 04:27 PM   #494
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Capri, what about the situation where it is 35 or 40˚ in the morning when you check tire pressure, and then you drive south and temps are up to the 90's or above. Wouldn't it be normal for pressure to go up more than 10% in such a circumstance? This type of radical temp change is quite possible in the Rockies. I suppose it could happen in reverse to, but you'd have to drive from late afternoon to dawn.

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Old 07-05-2013, 05:48 AM   #495
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Had a rather interesting set of readings yesterday on a trip to the upstate and drove the 2500 HD. We did about a hundred mile run at 55-60 and pulled into a Burger King and I got out quickly and went around and did temps. I did side walls and readings ran between 105F and 112F. The tread temps on all four were 120-122F. Ambient temp was 80s to mid 90s and humidity was a killer.

Three of the four sidewalls were 110-113. I could not find my air gage to correlate temps and pressures but remember the 105F side wall was right front so the plan today is to check the pressures in the tires and see the differences between the right front and other three on the theory that if I can correlate the combo that will keep the lowest side wall temp then that is the way to go.

Yesterday was hot and muggy and we were running in different directions E, S and W on dry roads, wet roads (rain) , sunny, overcast conditions and the last thirty miles was all overcast so no sun on side walls.

Thought I would duplicate the pressure of the right front in the other three and see what kind of temps I get next week in our trip to Alabama on the theory that if all the tread temps are the same and one had 6% lower side wall temp, then it can't hurt to lower the side wall temps on the other three if possible.

The Matco IR gave me readings in like half a second and I had all four readings in maybe 30 seconds with the 105F reading being the third tire checked.

Then go back around and check pressures with a dial gage I have and record the pressures by tire.

My thinking now is I have a Olympus Recorder I got that I cannot transfer the recording to my computer with so I will just leave it with the IR and the plan now is pull in to stop turn the recorder on and moving quickly do a fast walk around recording side wall and tread temps and any other thing I can think of like sun direction etc and perhaps road temp and maybe can work up a log where I can adjust pressures in an effort to attain the lowest side wall temps as it appears the tread temps were all within .02F.

It will be 300 miles each way so we will stop for breakfast, lunch and upon arrival so I can have four readings making sure I start with same pressures in all four tires.

If anyone else has any ideas/thoughts or other ideas please post them.

I have a easily portable compressor ( weighs maybe 30 lbs) and a air tank that will take 125 PSI so I am figuring I can raise/lower pressures as needed and keep the tank maxed out at hotel stop.

The recommended cold pressure on my E range tires is 80 PSI.
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Old 07-05-2013, 06:11 AM   #496
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Capri, what about the situation where it is 35 or 40˚ in the morning when you check tire pressure, and then you drive south and temps are up to the 90's or above. Wouldn't it be normal for pressure to go up more than 10% in such a circumstance? This type of radical temp change is quite possible in the Rockies. I suppose it could happen in reverse to, but you'd have to drive from late afternoon to dawn.

Gene
Gene,

Obviously there are all sorts of scenarios out there. This is a "Rule of Thumb", not some Federal Law that must be obeyed. "It's more of a guideline, than a rule."

I hope you get my drift.
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Old 07-05-2013, 07:15 AM   #497
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I just couldn't stand it any longer so I went out and dug out my dial air gage and went and checked the pressures. The 105F sidewall had 69 lbs at 75F Ambient. The other three tires had 70lbs and the above differences in side wall temp. Since I was obviously 10lbs under yesterday and not running at recommended pressures then we are talking apples and watermelons. haha.

It has been a month since I checked the TPs as the 2500HD stays under a shed in almost complete shade for three/four weeks at a time. When I pulled the AS out I added air to all 8 (AS and 2500) about a month ago and when we didn't go to Charleston pulled both back to their places in the shade under the shed.

Now all four have 80 lbs at 75F ambient. We will go to town today and I can get a reading at 25 miles for kicks and see what we have. Since the truck is snow white I guess I will just use IR to take ambient temp off the shady side of the truck body.
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Old 07-05-2013, 08:55 AM   #498
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Capri, what about the situation where it is 35 or 40˚ in the morning when you check tire pressure, and then you drive south and temps are up to the 90's or above. Wouldn't it be normal for pressure to go up more than 10% in such a circumstance? This type of radical temp change is quite possible in the Rockies. I suppose it could happen in reverse to, but you'd have to drive from late afternoon to dawn.

Gene
Good question and one with which I too have wrestled over the years. The manufacturers of the tires are not specific on this issue but I do know from aircraft tires that tests and ratings are supposed to be done at STP known as Standard temperature and Pressure or 20 deg C at 30mb I believe. Since temperature rises and falls by about 1 psi per 10 deg F, in theory at 40F you should see about 3 psi less than your nominal rating at 68/70 deg F. This also means that our friends in Phoenix checking their tires at 6 am and 90 F should also be 3 psi over the nominal rating. Here in TX I usually put 82 psi in my 80 psi (max) tires at 7 am when its already in the 80s.

Which then raises the issue also asked about what is the "expected" running temperature. The post that used the yardsticks of 10% and 20% is correct in my opinion. These are the markers used by the TPM systems. Put another way - if you roll out with 80 psi, and 12.5% increase gets you to ~92 psi or a 12 psi increase. At 10 deg per 1 psi that puts your tire temp at ambient (80) plus 120 or 200 deg. That's hot and a warning is justified. In my race car I look for 160-180 as my best grip operating temps and at 200 I am over driving the car.

On a recent 4 hour (non stop) stint though OK running N/S on I-35, my sunny side tire was at 135 and the shaded tire at 125. this was the same on the tow truck and the trailer and both were loaded to max. Speed was 60 most of the time.

But this has also been my M/O for years and I have blown 2 dozen tires. At least 6 of these were a trailer design issues when I upgraded/replaced the axles but the others...My theory is that the ST tires (as so many have commented) are not built to any specification close that printed on their side walls. The Chinese who make all these ST spec tires (although there are rumors that the GYM is now being made in the USA again) can hardly be accountable to anyone for their design spec and furthermore who is going to be able to do anything about a systemic failure problem at below let alone close to gross weight. My guess is that they role a tire against a nice smooth mechanically driven roller at the specified loading for some mileage and if the tire lasts they conclude its good enough to build and sell..at best. But add our road conditions, hours of running at 100 deg ambient and 120 plus surface temps, and at gross weight, they are not going to last. Nor will LT tires but the order of magnitude of the difference in survivorship is considerable at say <5K for ST tires and +15K for LT depending on heat, road conditions and speed which affects both heat and road impact.
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Old 07-05-2013, 09:12 PM   #499
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Sometimes I wonder when reading these tire threads. Are we trying to make rocket science out of common sense?

This is what I do and I call it common sense.

I have a 3/4 ton diesel truck and a trailer with a GVW rating of 10,000 pounds. I have a HawksHead TPMS.

I inflate my 16 inch tires to the side wall listed max pressure (80PSI)

I inflate my truck tires to the values stated in the trucks manual for fully loaded.

I check all of these at the beginning of each trip. Every time we stop, I do a walk around and visually inspect both truck and trailer. I do not whip out my IR thermometer (I do have one) and check the tire temperatures. That is the TPMS's job.

To me this is the bottom line:

Follow the manufacturer's instructions and specifications. Buy a good TPMS that monitors both the tires' pressure and temperature. Install it correctly and rely on it to do its job.

Remember: the worst thing that will happen from running the max rated pressure is shorter tire life. The worst that can happen for too low a pressure is a catastrophe. For me the extra money I might spend replacing tires more often combined with the price of the TPMS is my insurance against catastrophe.

I would much rather enjoy my travels with peace of mind, than constantly worrying about what my sidewall temperature is and the ramifications of that value.

It is interesting to know these factors that effect tire safety and life. However for those that don't find interest in such subjects, it will suffice to following manufactures specs and monitor these parameters with a well engineered monitoring system.

Ken
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Old 07-06-2013, 07:01 AM   #500
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......... but I do know from aircraft tires that tests and ratings are supposed to be done at STP known as Standard temperature and Pressure or 20 deg C at 30mb I believe.......
A couple of thoughts:

STP for chemistry (IUPAC) = 0C (32F) and 1 bar (14.5 psi,. 0.986 atm)

STP as defined by the NIST (National Institute for Standards and Technology, a US government agency) = 20C (68F) and 14.7 psi ( 1 atm, 1.01 bar)

And - No! - Tires are NOT tested at those conditions. There is some variation, but for endurance testing, tires are generally tested in 100F rooms.

And lastly, I think the tire manufacturers are pretty clear on this - pressures are to be set at ambient conditions. So regardless of what the temperature is, the cold starting pressure is the same.

Yes, a 10F change in ambient temperature will change the pressure by about 1 psi for passenger car tires (about 35 psi) and it will be close to proportional for higher cold pressures, but that doesn't change the recommendation. And, yes, starting out the day when it's hot and going to a cold temperature is going the wrong direction - BUT - these situations are rarely encountered.

I would advise not to over-think this. The burst pressure for tires is way, way over the maximum written on the sidewall, so tires are not in danger of bursting due to pressure.

If you want a "Set it and Forget it" approach to things: Set the pressure on a cool day - in the 40's. Or adjust the starting pressure so it is OK at 40F. A bit of over pressure is not significant - including tire wear.
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Old 07-06-2013, 08:44 AM   #501
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Kiss...

CapriRacer said it well above: "If you want a "Set it and Forget it" approach to things: Set the pressure on a cool day - in the 40's. Or adjust the starting pressure so it is OK at 40F. A bit of over pressure is not significant - including tire wear."

In a galaxy far away and in my previous life as a navy carrier pilot, we flew with the main mounts inflated with pure nitrogen at 300psi to withstand extreme energetic cat shots and the pounding forces of arrested landings. Pressures were monitored before and after every flight - in some cases, that meant 6-8 times daily.

Point being, if you really want a "Set and Forget it" solution, as Capri suggests - pay the extra few bucks for Nitrogen, or get it free at some tire shops.

There's some benefits in running Nitrogen in both your TV and AS:

1. Nitrogen is a gas and is still affected by changes in ambient temperature (about one psi for every 10 Fahrenheit). Nitrogen filled tires will require pressure be added during the fall/winter months as ambient temperatures and tire pressures drop. Nitrogen is good but can't change the laws of physics.

2. Nitrogen reduces the loss of tire pressure due to permeation through rubber over time by about 30%. This helps maintain the required tire pressures a little longer, but doesnt eliminate the need for monthly tire pressure checks. This is good for people who choose the "Set it and Forget it" approach.

3. Nitrogen is non-corrosive and will reduce oxidation and rust due to the absence of oxygen and moisture. This will help minimize wheel corrosion to promote better bead sealing. Tires that are used routinely will be replaced long before any life benefit would be received by using Nitrogen. This is most beneficial for those who use their Airstreams infrequently.

4. Nitrogen is a dry gas and will not support moisture that could contribute to corrosion of the tires steel components (bead, sidewall reinforcement and belts) due to the absence of moisture over extended periods of time. However its important to remember that atmospheric pressure is constantly pushing oxygen and moisture into the rubber from the outside of the tire. This is especially good for low mileage those who don't wear out their tires quickly or those that run average annual mileages but use long wearing radial (60K and 80K warranted) tires.

5. Nitrogen assures more consistent pressure increases due to increases in operating temperatures in environments such as the Rocky Mountains/Sierra Nevada (low morning, high afternoon temps) because of the absence of moisture.

6. It is OK to use standard air if pressure adjustments are required when a local source of Nitrogen cant be found during a trip. While this reduces the benefit of higher Nitrogen content, it is far better than running the tires under-inflated in search of a source for Nitrogen- thus, increasing the chance of a tire failure. Often the original Nitrogen provider will refill the tires for free or a nominal cost when the driver returns to his hometown.

My final $0.02, KISS: find a comfortable personal balance between using your TPMS, IR temp gauge, manual pressure gauge, multiple daily monitoring efforts, and keeping your entire running gear system safe and effective while all the time maintaining the peace of mind that you won't have a catastrophic tire failure as you're 'streaming down the interstate.
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Old 07-08-2013, 12:47 PM   #502
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I was referring to the NI STP definition that we also use to define engine performance in a aerospace and automotive analyses. But given the logical use of percentages to figure psi change with temp the guideline at the higher inflation levels of E,F and beyond works out more closely to 2 psi per 10 deg F. Meaning that at a running temp of say 130 F (Summer in the South on the Sunny side) that is a delta of 60 deg or Plus 12 psi putting the tire at 92 psi assuming you started at STP and nominal max inflation of 80 psi. By my math (often faulty) thats an increase of 15% at which point my Pressure Pro TPMS would be hollering loudly. Put another way, if the internal tire temp hits 130 by most definitions you have a problem. I have seen something close to this at 127 deg at 100 ambient and 130 surface (by IR thermometer) so was sailing close to a limit that had I been in say AZ rather than OK and TX would have caused me to pull over.

As for Nitrogen as the panacea of all these problems my experience also matches all the points made with one proviso - its still hard to find outlets equipped to deflate the tire (without losing the bead seal) and reflating. Had I that opportunity I would grab it. The major issue IMO is not the stability of N2 but rather the lack of moisture in the content. That moisture creates effectively a super heated steam inside the tire that makes any amount of temperature problem that much worse. Like a sauna effect!

Final point - the ability to fill and forget is a luxury that is only obtainable by having a rig that can be operated at a considerable (25%) margin below the max load for the tire. I unfortunately do not have such equipment and its not made by anyone anywhere so I am trying to learn all I can about the risks of operating so close to the limits of E, F and G tires as opposed to China Bombs.
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Old 07-08-2013, 12:55 PM   #503
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I have a 3/4 ton diesel truck and a trailer with a GVW rating of 10,000 pounds. I have a HawksHead TPMS.

However what are your axle loads realtive to the GVW and the GCVW? when I did as you have I was bitten by the fact that although I was below my GVW and GCVW I was over the axle load limit as imposed by the rear tires because of the effect of a 1400 lb hitch weight.

A gotcha thats only solved with 17.5 or 19.5 wheels G rated tires
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Old 07-08-2013, 02:05 PM   #504
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Vlamgat, I'm unsure where you got a delta of 60 degrees. While I have not worried about calculating the temperature and pressure increase throughout the day. I have seen no pressures like your calculations predict.

Here in Phoenix, when I check the tires before pulling out, the ambient air temperature at 8:00-9:00 AM is already around 95 degrees headed to 100+ in another hour or two. The overnight lows are around 90, and that's at 2:00 AM.

With daytime highs around 110-115 most days, that's only a difference of around 15 degrees (95 to 110), maybe 20.

If the temperature a couple of feet above blacktop is 120 degrees, that's still only 25 degrees, which equates (on your 2 psi/10 degree differential) to a 5 psi increase.

I maintain 80 psi in our Michelin XPS Ribs, all year; and in the summer, after verifying 80 psi at 8:00 AM, I used to measure tire pressure increases of zero to 2 psi after driving an hour.

Note: I no longer check tire pressure while on the road; and instead, use an IR thermometer to monitor changes in tire temperature. If the temperature is the same as the last stop and a tire doesn't look low, I assume the tire pressure is still OK. I acknowledge that this isn't very scientific, but it's better than not checking at all.

From years of towing in the desert southwest, I have never seen an increase in tire pressure from 80 to 92 psi while driving. And, while I would never intentionally increase the cold tire pressure to 92 psi, a tire probably wouldn't be damaged by this unless run at this pressure consistently, which would cause abnormal tire wear. Tire manufacturers state that a slight increase in psi is normal; and pressure should not be reduce when hot, if cold reading was at or below the maximum sidewall pressure.

I understand your concern regarding tires and tire pressure. However, from a practical standpoint, about all one can actually do is install the best tires one can afford (or justify), pump them up to the maximum sidewall pressure, and hope for the best. That's what we did by replacing our ST tires with XPS Ribs and inflating them to 80 psi. And, after verifying 80 psi before pulling out, we don't worry about our tires again.
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