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Old 11-20-2022, 06:26 AM   #1
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Tire pressure

2022 Bay Star Sport 3226 with the Goodyear G670 tires. I run my tires, based on the coach’s weight, at 95 in the front (placard says 95) and 100 for the rears ) placard says 95). I left Tennessee the other day when the temperature was 35 degrees, headed to Florida. Once in Florida, the temperature was approaching 80 degrees. My TPMS was indicating my rear tire pressure has increased to 127. I clearly understand the pressure increases based on the air temperature however, my question is whether or not 127 is too high. I would think that pressure would still be within the tires PSI capacity in that someone running with the maximum cold pressure of 110 driving on a hot day would likely see their pressure go above my 127.

Thoughts?

Thanks!
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Old 11-20-2022, 06:51 AM   #2
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The simple answer is NO. Tires are designed knowing that pressure increases will occur with tire temperature.

Click on this LINK. It is an article about just this question.

Set the pressure at "your" ambient cold temperature and drive on. From now, until your next cold inflation check, monitor for LOW pressure. The high pressure not so much. The article was written by the late Al Cohn who is a recognized expert in truck tire maintenance.
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Old 11-20-2022, 10:27 AM   #3
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Tire pressure

Only worry about setting cold pressure not hot. As long as your inflating tires at or below max cold pressure stamped on sidewall at ambient temp and not overloaded your good

Mine go up about 15 psi on hot days if I saw one running significantly hotter (via higher pressure) than the rest I would pull over and check it thats about it.
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Old 11-20-2022, 10:37 AM   #4
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Quote:
Originally Posted by yeloduster View Post
The simple answer is NO. Tires are designed knowing that pressure increases will occur with tire temperature.

Click on this LINK. It is an article about just this question.

Set the pressure at "your" ambient cold temperature and drive on. From now, until your next cold inflation check, monitor for LOW pressure. The high pressure not so much. The article was written by the late Al Cohn who is a recognized expert in truck tire maintenance.
Thanks for sharing the link. The article notes that you should not adjust your pressures when the outside temps drop. I have always been told and have adjusted when the seasons change. Is he suggesting that you should set the PSI at 70-degrees and just leave it? Or is that comment more for OTR drivers that are going to see a wide range of outside temps? Doesn't seem right to me...
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Old 11-20-2022, 11:04 AM   #5
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Quote:
Originally Posted by Wacdmc View Post
My TPMS was indicating my rear tire pressure has increased to 127. I clearly understand the pressure increases based on the air temperature however, my question is whether or not 127 is too high. I would think that pressure would still be within the tires PSI capacity in that someone running with the maximum cold pressure of 110 driving on a hot day would likely see their pressure go above my 127.
May I ask for some clarification?

You state: "My TPMS was indicating my rear tire pressure has increased to 127."

I'm presuming that you have four sensors on your rear dual wheels, one for each tire. Were all four tires indicating 127psi? What were your front tires indicating?

If all four were indicating 127psi, and your front tires were indicating a similar rise, my first thought would be that it's probably OK. If one of the steer tires were indicating significantly different from the other or, if one of the four drive tires were significantly different from the other three, I'd be inclined to investigate further.

My first step would be to use a tire pressure gauge to confirm the readings. IF the tire gauge confirmed that the TPMS was accurately reporting the tire pressure(s), I'd be inclined to determine why one tire was experiencing a different pressure rise than its corresponding twin location tire. Since pressure is directly proportional to heat build-up, I'd want to know why one tire was heating more than its twin. Potential reasons that come to mind include solar radiation, a bad wheel bearing, a dragging brake or engine exhaust.

We can have a predisposition to presume accuracy when presented with a digital display. That may not be well founded in fact.

Take care,
Stu
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Old 11-20-2022, 03:28 PM   #6
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Your tire pressures should not be set to what the placard says. That's a starting number. You need to get your rig weighed, and then get the tire manufacturer's chart for the correct pressure.
In my experience, if you use the placard pressures, your ride will be like in a conestoga wagon. Remember, the coach manufacturer doesn't always know what tires you have on, only you do.

Bill
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Old 11-20-2022, 08:24 PM   #7
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[QUOTE=777 Driver;6362525]May I ask for some clarification?

You state: "My TPMS was indicating my rear tire pressure has increased to 127."

I'm presuming that you have four sensors on your rear dual wheels, one for each tire. Were all four tires indicating 127psi? What were your front tires indicating?

If all four were indicating 127psi, and your front tires were indicating a similar rise, my first thought would be that it's probably OK. If one of the steer tires were indicating significantly different from the other or, if one of the four drive tires were significantly different from the other three, I'd be inclined to investigate further.

My first step would be to use a tire pressure gauge to confirm the readings. IF the tire gauge confirmed that the TPMS was accurately reporting the tire pressure(s), I'd be inclined to determine why one tire was experiencing a different pressure rise than its corresponding twin location tire. Since pressure is directly proportional to heat build-up, I'd want to know why one tire was heating more than its twin. Potential reasons that come to mind include solar radiation, a bad wheel bearing, a dragging brake or engine exhaust.

We can have a predisposition to presume accuracy when presented with a digital display. That may not be well founded in fact.

Take care,
Stu[/QUOTE

I should have been more specific and stated one of the rears was at 127 and this was the highest pressure of all rears. Front also increased about the same percentage but since they were set at 95, they were about 5 psi less than the rears.

Based on the responses, appears I don’t have anything to worry about.

Thanks.
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Old 11-20-2022, 08:24 PM   #8
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Quote:
Originally Posted by yeloduster View Post
The simple answer is NO. Tires are designed knowing that pressure increases will occur with tire temperature.

Click on this LINK. It is an article about just this question.

Set the pressure at "your" ambient cold temperature and drive on. From now, until your next cold inflation check, monitor for LOW pressure. The high pressure not so much. The article was written by the late Al Cohn who is a recognized expert in truck tire maintenance.
Thanks for this link. Good information.
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Old 11-21-2022, 07:49 AM   #9
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Quote:
Originally Posted by tomato View Post
Thanks for sharing the link. The article notes that you should not adjust your pressures when the outside temps drop. I have always been told and have adjusted when the seasons change. Is he suggesting that you should set the PSI at 70-degrees and just leave it? Or is that comment more for OTR drivers that are going to see a wide range of outside temps? Doesn't seem right to me...
I think there is a good reason for your confusion. The information available on the internet is confusing. Al Cohn seems to be saying the pressure should be set at cold inflation ≈70° F. By implication if you had to set the pressure at a different ambient temperature you should change your set point by ≈2%/10° F.

I've found other sources on the internet that imply that USA truck tire inflation charts are created at an index temperature of 68° F. I do not see the load inflation charts state a temperature for setting cold inflation.

My 2¢ say it makes sense to adjust pressure with an eye on ambient temperature. If I needed to set pressures at ambient 30° F I would decrease pressure by 10% (2% per 10° F). My normal 100 PSI would become 90 PSI.

My brother was an OTR trucker for years. He was based out of Vernal, UT. In the winter it may have been -10° F when he left the yard in Vernal and 12 hours later he was somewhere in north central Texas where the ambient temperature was ≈70° F. His normal cold inflation pressure for his trailer tires was 100 PSI. When he checks them in Vernal they are 84 PSI. He calls that good knowing the pressure will rise as soon as the tires start rolling and the pressure will be "spot on" by the time he gets to Texas. Had he readjusted his pressure while the temperature was -10° F he would be severely over inflated when the temperature is 70°.

I know, you say that is just for OTR truckers. However, I live in Colorado and most of my trips are to the high country. It may very well be 38° F in July when I leave a campsite at 7 AM and be 90° F when I get to Pueblo. I have the same tire pressure/temperature issues as the OTR trucker! You may have these same issues too if you decide to visit and camp in GOD"S COUNTRY!

Again my 2¢, TPMS can give us too much information. The seemly wild pressure fluctuation can lead us to taking unnecessary action and/or unnecessary worry. If you have TPMS you need a good understanding of what temperature does to the pressure and what you should do (or not do) about it.

Attached is a chart defining pressure vs temperature up to 100 PSI.
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