I get that you should only set the air pressure in your tires when they are "cold". That is, before you start driving on them. But tire pressure rises and drops with the ambient temperature. So setting your tire pressure when its 30 degrees F out versus when it is 90 degrees F out can mean maybe 10 PSI difference. Maybe more? So do you adjust the pressure based on the air temp? That is, put a little more in when its cold out and a little less when it is hot out? It probably doesn't matter as much when running the truck empty but might make a difference when you are loaded down and towing.

 

Since I always check the tire pressure, ambient, cold, on the 5th wheel and adjust as needed before towing, it's not that much more to check the truck tires while I'm at it, especially since I air down about 5 PSI when not towing. So what ever season it might be, my pressure is good for that trip.

As you say not a big deal empty or not towing. And I get your point, even if you are overthinking just a bit.

 

and your tire "gauge" pressure will change with atmospheric pressure, so at the top of the hill your tires will have more pressure in them. I have noticed this while traveling where there is a drastic elevation change.

 

Despite what people trying to sell you nitrogen for your tires, whatever is in the tire obeys gas laws. When you get to temperature extremes is where you see consequential differences. Always as a matter of safety, check tire pressure cold. When I check it hot, I always bias an extra five pounds to try to account for the expansion. The problem with airing up tires hot is that your running pressure is too low and the tire will heat up more. So, you check it hot again and notice it is above spec and let more air out and run it, and check it again, and it is again above spec, and you let out more air and shortly after that, your tire comes apart from the heat.

 

I believe the "cold" tire ratings are at ISA which would be 15c/59f...

There is a chart somewhere on what pressures do at temps above and below that.

 

Correct….AND barometric pressure of 29.92, at Mean Sea Level.
Conversion charts for all of these parameters.

 

I normally run 78% nitrogen. Along with that I will check air pressure in tires monthly, more often if the temp suddenly goes from 70 to the teens or the other way around. I try to get to them in the morning before one side or the other has been in the direct sunlight for a period of time. Low pressure in tires = excessive heat , who can remember the Ford debacle with the Explorers having blowouts and rolling down the highways? IIRC the reason was Ford wanted a smoother ride so they called for a lower air pressure than Bridgestone/Firestone recommended for that tire. Heat caused tread separation and then the Explorers would sometimes roll, occasionally with very bad results for the occupants.

bob

 

Yeah, me too. That mix is both plentiful and cheap.

 

You mean Exploders? lol

 

I've been using the 78% nitrogen, 21% oxygen mix also for over 60 years without issue. I find it makes a nice smooth ride and it's a much more reasonably priced alternative to the pure nitrogen being pushed and sold at some of the tire dealers.
Went to a quick oil change place and a young kid comes in and says to me that there is a problem with my truck. "what kind of problem?" Some one has changed the tires. I said nobody has changed the tires, they came on the truck. He says there're not original because the tire says 80 and the door sticker say 60/65. Then I realize he's talking about the required air pressure. So I then had to educate him on required tire pressure verse max tire inflation. Just can't get good help anymore.

 

As others have said there is a standard to se the tire against. But it's not always practical to wait till that happens or bring the environment to that. Also realize that the pressure rating on the door jam is for the tires supplied with the truck. So if you put different tires on that pressure rating may not be correct any more (unless you changed to a very different tire or size you'll likely be the in a similar range). Generally tires will a change a similar number of degrees and PSI from cold to hot (separate from summer to winter if properly inflated and loaded). So if tire temp goes up by 10 degrees in the summer after driving it will also go up by about 10 degrees in the winter after driving. Also tires do loose air over time, so don't forget to also check the spare too (no fun finding the spare low or flat when you need it). I set my tire pressures to same pressure irrelevant of the ambient temperature when the tires are cold. Occasionally I might have to drop the pressure in the spring but that is only if I happen to top off the tires late in the winter and it was unusually cold. I also rarely max out the payload and usually am empty so tire pressure is more for comfort and tire longevity. But when I know I am going to have something heavy in the bed I up the pressure (but never more than the tire is rated for).

 

Atmospheric pressure only varies 4.5psi from sea level to 10,000'. Not enough of a change to worry about. Temperature will be more of a factor.

 

You must live in Texas with 90 degrees one day and 30 the next. Seems like that's how it is in South Texas anyway

 

I like kicking in that ~1% argon and a trace of carbon dioxide and other gasses just to make it perfect

 

To me, cold tire pressure means before it's driven, regardless of outside temperature.