Tire Pressures

[Just4Fun20]

I'm truly sorry since there are many posts on tire pressures.

My specific question is: What "cold" temperature is appropriate for properly setting my tire pressures? Details follow.

I've a 2018 Entegra Aspire. I had weights done and I'm at about 90% of GVWR and everything is balanced and within limits. That's not terribly important to my question.

For reference: My placard says:
STEER (Front) TIRES: 130 LBS
DRIVE (Main, Dual) TIRES: 85 LBS
TAG TIRES: 95 LBS

My tires are: Michelin XZA-1 (Front/Steer) 315/80R22.5
Michelin XZA-2 Energy (Rear - Drive/Tag) 295/80R22.5

Entegra and/or NIRVC said to run them at placard pressures, based on my weights, but I think I may change to the Michelin numbers... Say 120 / 75 / 80 (vs the current 130/85/95) which aligns more closely to my axle weights and the Michelin inflation charts.

Now, my question. Those are to be measured "COLD". OK, no problem. Take the readings in the morning. I have a TPMS (Tire Pressure Monitoring System) so I know my Tire Pressures each day (that I drive). My problem, or question is... at what temperature?

It's been cold lately. If I read the tires and it's 32 degrees that is very different than reading the tires when they're at 60 or 70 degrees. For example, my steer tires the other day read 108 lbs at 32 degrees. A bit low, but after they'd warmed up to 60 degrees they were at 130.

Adjusting them each time I drive, based on ambient "cold" temperature doesn't seem like the right answer. Any advice on taking temperature into account for my "cold" tire pressure readings?

NOTE - Entegra suggested I call Michelin. I called Michelin (twice), which was a complete waste of time.

So, I'm turning to the experts and the place where I've always received good, knowledgeable replies... this forum.

Thanks in advance.

[450Donn]

The correct answer is weigh each corner and set the air pressure per Michelin load chart. The simple answer is, set air pressure according the chart listed on the vehicle.

[JohnBoyToo]

cold pressure is just that as measured with the CURRENT ambient temperature....


and, no, you don't need to change it every day unless the temp goes from 10 degrees to 100 degrees in 10 hours, you won't notice the difference in the cold pressure...


Now, driving will warm you tires up somewhat relative to the amount of flex the sidewalls have as you go down the road...



so set your psi to a bit above the weighed cold psi and enjoy !

[Lv2Roam2]

I set my Michelin 295s and 275s at 70 - 75 ambient temps. Michelin was also noncommittal when I called them.

At ambient just less than 40 my AM pressures will be down ~ 10 lbs - I don't adjust for that. At ambient < 30 pressures can be down ~ 15 lbs; if I'm on the road I'll pressure up - otherwise I don't adjust.

[Rollin101]

I think the answer you’re looking for is 72 degrees, but I think anything between 70-80 degrees is ok.
No you don’t need to adjust them every time the temp changes.

[MRUSA14]

The placard in your coach shows maximum rated tire pressures which is almost never the correct pressure for your loading.

You should fill the tires at a cold pressure close to the ambient temps in which you will be driving. If you go temporarily from warm to cold for a few hours it is probably no problem, but if you drive from warm Florida to cold Michigan in winter, you should add air to bring your cold tire pressures back to your normal pressure as shown by the Michelin load charts, because you will now be operating primarily at lower ambient temps. For example, you do not want to drive in sub-freezing temperatures for weeks or months on tires that were inflated properly at an ambient temperature of 72, because the pressure in your now cold tires will be too low.

Low pressures can be harmful to your tires. Slightly high pressures are not, unless the maximum pressure printed on the sidewall is exceeded. Therefore, I run my pressures at 5 PSI over the Michelin chart to give me a safety margin in case a little pressure leaks out. This also gives me some pressure cushion in case I fill tires at ambient pressure of 75 and then the ambient temps drop to 40, thus lowering the tire pressure.

[lwmcguire]

Tires fail due to overheating from low pressure below the load psig rating

Error on the high side

Many people wonder why the down wind tires fail while traveling in very hot weather

Anyone traveling a lot sees all the tire parts scattered in hot weather

The smartest people add a bit to the charts to allow for load changes and the other variables

Folks with poor suspension systems
their tires INMHO

[HJLowell]

Regardless if you have a tire monitor or not.
We check tire temps manually every time we stop during a trip.
Fuel stops, rest stops etc.
We take tire surface temps, sidewall temps & hub temps. Always have.
Before the temp guns We used our hands.
Sometimes the reading triggers a need to add air. During hot weather I have dropped my speed back 10 mph.
Till the sun sets or so.
It was so hot in western Kansas one August we pulled into a village park and sat it out for 3 hrs.

The above posters are correct about high heat being your worst enemy.

I set my cold tire temps between 60 and 75 degrees if possible.

You can alway re adjust if needed.

Fortunately we have not experienced a blowout traveling.

My wife does a walk around with the heat tester gun each time we stop.
And a walk around before we take off each time checking lights, toad pins,
storage doors or trailer
connections, chains, brake safety wire etc.

Three times in the past 2 years she saw a thin film of oil on the rock guard that triggered an inspection and we fixed.

[jadatis]

Originally Posted by Just4Fun20

I'm truly sorry since there are many posts on tire pressures.

My specific question is: What "cold" temperature is appropriate for properly setting my tire pressures? Details follow.

I've a 2018 Entegra Aspire. I had weights done and I'm at about 90% of GVWR and everything is balanced and within limits. That's not terribly important to my question.

For reference: My placard says:
STEER (Front) TIRES: 130 LBS
DRIVE (Main, Dual) TIRES: 85 LBS
TAG TIRES: 95 LBS

My tires are: Michelin XZA-1 (Front/Steer) 315/80R22.5
Michelin XZA-2 Energy (Rear - Drive/Tag) 295/80R22.5

Entegra and/or NIRVC said to run them at placard pressures, based on my weights, but I think I may change to the Michelin numbers... Say 120 / 75 / 80 (vs the current 130/85/95) which aligns more closely to my axle weights and the Michelin inflation charts.

Now, my question. Those are to be measured "COLD". OK, no problem. Take the readings in the morning. I have a TPMS (Tire Pressure Monitoring System) so I know my Tire Pressures each day (that I drive). My problem, or question is... at what temperature?

It's been cold lately. If I read the tires and it's 32 degrees that is very different than reading the tires when they're at 60 or 70 degrees. For example, my steer tires the other day read 108 lbs at 32 degrees. A bit low, but after they'd warmed up to 60 degrees they were at 130.

Adjusting them each time I drive, based on ambient "cold" temperature doesn't seem like the right answer. Any advice on taking temperature into account for my "cold" tire pressure readings?

NOTE - Entegra suggested I call Michelin. I called Michelin (twice), which was a complete waste of time.

So, I'm turning to the experts and the place where I've always received good, knowledgeable replies... this forum.

Thanks in advance.

About the pressure to use, it migt be better different then you planned, but for that I have to know weights, and 3 axles makes it more complicated, can you adjust the tag .

For the temp , advice is given for 65 or 68 degr F.
And goal is that not any part of tire overheats when riding the speed for wich it is determined.
When colder》lower pressure》 more deflection of tire》more heatproduction at same speed. But then also more cooling down because of the more temp-difference between rubber and in and outside air.
When hotter outside the other way around.
My conclusion is that within a sertain range of outside temperature, the heatproduction and cooling down stays in balance, so still not any part of tire overheats.
So you have to calculate back the pressure to 65/68 degrF.
For that I made lists, will give it in next post, cant manage on my mobile now. EDIT managed to edit the list.
Use it next way.
Measure pressure and note outside temp.
Look in list at the outside temp,and look on that row for the measured pressure. Then go down or up in that kolom to the 65degrF and that is the pressure to compare with advice.
Interpolation is allowed, and thoug given in digits behind point, you can never be that acurate.
For instance the difference between 65 and 68 degr F is neclectable.

Cold pressure is when inside tire temp = outside/ambiënt temp, that simple. So measured when not driven yet for hours, and no sunshine on tire, at outside hot temp of 100 degrF is still cold pressure.

[bill2011]

Originally Posted by MRUSA14

The placard in your coach shows maximum rated tire pressures which is almost never the correct pressure for your loading.

You should fill the tires at a cold pressure close to the ambient temps in which you will be driving. If you go temporarily from warm to cold for a few hours it is probably no problem, but if you drive from warm Florida to cold Michigan in winter, you should add air to bring your cold tire pressures back to your normal pressure as shown by the Michelin load charts, because you will now be operating primarily at lower ambient temps. For example, you do not want to drive in sub-freezing temperatures for weeks or months on tires that were inflated properly at an ambient temperature of 72, because the pressure in your now cold tires will be too low.

Low pressures can be harmful to your tires. Slightly high pressures are not, unless the maximum pressure printed on the sidewall is exceeded. Therefore, I run my pressures at 5 PSI over the Michelin chart to give me a safety margin in case a little pressure leaks out. This also gives me some pressure cushion in case I fill tires at ambient pressure of 75 and then the ambient temps drop to 40, thus lowering the tire pressure.

This information is very helpful to me as we are about to leave Florida and travel back to Canada. I planned to check and adjust air pressure before I leave but never would have thought about the effect of colder weather during our trip. Thanks for posting this.

[GeezerViz]

There are comments here about tires overheating and taking the temperature of the tire periodically. At what temperature are tires too hot? I have a digital thermometer but I'm not sure what I should be looking for.

[MRUSA14]

Tires heat up as you drive, and the pressure goes up as a result. If the cold pressure was set correctly, expect to see an increase of 10-15% as you drive. The sunny side will be warmer than the shaded side. These increases in temperature and pressure are normal and expected. Do not release air pressure to compensate for this.

There will be normal differences based on tire position or whether the tires are on the sunny or shady side of the coach. When checking temperatures with my TPMS or my IR thermometer, what I am looking for is a tire or hub that is significantly hotter than the others. Some differences are normal. Most of your tires should be within 10% of the other tires on the same axle. If you see one tire that is 15-20% or more higher in temperature, or more than 10% higher or lower in pressure than the others, it is time to investigate.

[Gary.Jones]

There is a known industry standard on what an excessively hot tire is.... at one point I was told that temperature. I think that I was told that number by the factory rep for the Valor Tire Monitoring system that I have on my coach. I think the number (listen - I think the number I was told) was about 170 degrees. Whatever tire industry manufacturers group supposedly has set a standard that should always be considered dangerous.

Now I know my tires best by their tire pressures. I have my 365 cornerstone steer tires set for ~ 118 psi. I routinely see my tire pressures on those tires increase to the range of 135 psi on a warm day on the interstate at interstate speeds. As Mark and other have said, there are substantial tire pressure (and tire temperature) difference on our coaches based on whether the tire is on the shadow side of the sun of the direct sun side. All my tire positions increase at least 10 PSI as they get highway warm. Big differentials between tires in the same relative position and exposure should be noted as a concern. I also use my infrared thermometer to check all my wheel positions when I stop for a break.

I will try to call Don Rigby and get the industry standard number later today.

Gary

[Dieselgem]

If the tire gets near 155 it has my attention!