Okay, just being lazy here....

Check and set all my tires to the recommended 80psi about 5 weeks ago. Since then the heat has hit and they now read 84psi on my TPMS. Leaving for cooler climate tomorrow for a week so I'm sure they will drop once they sit for a day or so. Its only 60 miles in the heat before I get to higher elevation.

Do I drop them or tow with them 4psi higher.. it's a battle because if I leave them alone they will increase hut if I drop them they will be low when I leave camp to return home.

Its a constant battle when living in the desert and camping in the mountains..

Take an average and drop them 2psi? Or leave them alone?

 

When you checked them, was it in the morning before the sun started beating on them? I know it's not much, but being that you are knowingly moving to colder weather, I would just check them in the morning before you leave and if necessary air down to 80 while it is still cool. Just curious, how much of a temperature change? I think the "rule of thumb" is the tires will drop ~ 1 psi for every 10F drop in temperature.

 

The above is good advice, especially if you don't know what your trailer weighs and don't know what the tire manufacturer says the load rating is at various tire pressures.

If you can, check the tires before setting out, and while they've all been in the shade if possible.

I agree, I would check the morning you're leaving, if they are at or right around 80 then run with it, if they're above while in the shade drop them down to it. Depending on how much cooler it's going to be, it may not make much difference.

 

Trying to reset your tire pressure every time the temp changes is just crazy. I set mine at 115 psi (load range H tires) at 70 degrees at 2000 ft altitude where our home base is and never adjust the pressure again. Some mornings of it gets down into the 40s the low pressure alarm that set at 105 may be going off I just silent it and after a few miles down the road the tires are back into the high 120 to low 130 range just like they always run. When we leave Yuma in the spring at 220 ft altitude they will be around 110 to 112 and after a few miles down the road they go back to 120 to 130 range just like normal. Just find a cold temp your comfortable with and set the pressure and leave it alone.
Denny

 

I think the advice might depend on whether you have a portable compressor or not. I do, so I set mine in the truck and RV the night before travel from home or from camp. It's easy enough, and doesn't take long.

 

Checked them this morning closer to the time if day we will leave tomorrow and only 81-82 PSI so will mot mess with them this trip. They never see sun when it's stored on my side yard bug 109* ambient temp obviously makes a difference.... only going to be 100* in town and our camp site is at 7500' so temps will range from mid 70's to low 40's.... ain't chasing it for a couple degrees..

 

how much pressure do you actually need?

i bet if you scaled it, you wouldn't need to be at 80 psi.

as denny said, but in different words, you are over thinking it.

set the pressure before you head out and then stop fussing over it. Pressure is dependent on ambient temperature and barometric pressure. What do you think happens to your air pressure in the tire as a storm rolls in and the barometric pressure drops? The absolute pressure remains the same, but the gauge pressure will change - sometimes as much as a full PSI, but are you going to adjust for it as the weather changes? Doubtful

Show me your scale ticket and i'll help you get what the absolute minimum pressure is - i bet it is MUCH lower than you'd expect. I'd be willing to bet, that even with a heavily loaded trailer the math would show you to be safe well down into the 60 psi range.

you are in the weeds. set it and forget it. spend time worrying about something else.

FWIW, i've tended lately to run more lower than higher. The scale tickets tell me what i NEED and i adjust it close to that number. I've found that the tires wear better when they aren't aired up far above what the weight calls for. They can scrub more in the turns, though, so that's a thing .... but by and large, i've found that they wear more evenly across the tread face - for both the trailer and the tow vehicle.

 

It weighs in at 7600# on twin 4400# axles at last CAT Scale (axle weight). That includes a full 50gal fresh water tank just behind the axles.

 

All tires have the word "COLD" incorporated into the pressure ratings on the side of the tire, so I would set pressure after the tires have been sitting for hours, allowing all the internal heat from being worked to cool down to ambient temperature.

Practically speaking, this means checking tire air pressure before the first trip of the day (ie pre trip inspection). It doesn't have to be in the morning, if one does not drive during the day. If one sleeps and plays all day, and drives all night to the next destination, arriving at a camp sight in the morning, then it would not make sense to check air pressure first thing in the morning upon arrival, because the tires have been working all night to get there. This isn't said to say that you have done this... it is simply said as an example to help define the meaning of "COLD".

"COLD" in Arizona is different than "COLD" in North Dakota. Cold in terms of tires are tires that have been at rest for several hours, allowing all of the frictional heat build up to dissipate and settle down to ambient temperature in whatever climate you happen to be in.

There is one RV tire offered in the 16" wheel size that is Load Range E and is rated to 90 PSI, even though there is no difference in weight carrying capacity of this particular tire between 80 psi and 90 psi. (Michelin Agilis Cross Climate LT)

The Load Inflate Index Table for this LT tire has the same maximum capacity for every pressure increment above 80, up to 90. For this and other reasons, I selected this tire for my unused RV (Class C Motorhome), just to give the warm fuzzies whenever or if taking long drives over hot asphalt on sweltering days in summer months... all conditions that would cumulatively build up internal and external tire heat, which increases the pressure inside the tire by several PSi.

Even though inflated only to 80 PSI cold, Load Range E tires can reach 87 PSI when operated... and we have no choice but to assume that good tires manufacturers understand this, and build tires accordingly. Under this assumption, there is no need for an LRE tire to be rated at 90 psi, in order to safely operate at 87 psi, when inflated to 80 psi COLD.

 

Duplicate post

 

what size tire?

 

I have built in on board air on my truck so airing up is easy.

 

15" Goodyear endurance. 225/75 R15E.

Big letters on sidewall stating 80psi....

They ran about 88-91psi on the trip up yesterday. Feels ok to me. I monitor with a TST 507 TPMS system.

Ambient temp started out around 90* and ended up around 75*.

 

ok, so here’s the math:

each tire can hold 2830 lbs at 80 psi.
2830/80=35.375. So each psi increase in pressure can support about 35 additional pounds of load.

you said your camper weighs 7600 lbs on the axles.
7600/4=1,900. Each tire is carrying 1900 lbs

1900/35.375=53.71 psi. In order to safely carry 1900 lbs, the tire needs to be inflated to about 54 psi.

so if you are inflating your tires above 55 psi, you are safe.

this is why I said to stop worrying about the couple psi you are up or down in the morning on a cooler day.

what would I do?
id run them at 60 or 65 psi to soften the ride in the camper a bit. 80 psi is fine but it is waaay overkill for what you need based on your scale weight.

there are lots of papers on this. And with a load index over 100 you can actually lower it even further. But, the psi/lbs approach will give you a safe conservative way to reduce air pressure for the load.

if you look up load charts for that size tire, you will see that the numbers above are more conservative than the load charts I found from Goodyear.
Goodyear says that tire can support 2,020 lbs at 45 psi. So really, you could safely run them at 50psi or below.

so worrying about 78psi on a cold morning is not in the realm of things you really need to worry about.

 

Damn, you really know your tires. I may drop them a few PSI to see if i notice any ride difference.

Its got the Road Armor shakles so they help too...