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Danny5 07-16-2018 12:43 AM

Tire Pressure vs. Altitude
 
I've been trying to search for information on proper tire inflation vs. altitude changes, and really haven't found anything. All I read about is people stating inflate to max PSI on a cold tire. Well, I have a good head scratcher for you!!!

I started my trip at 1000' above sea level, with an ambient temperature of 112 degrees. My D rated trailer tires were inflated to 60psi. As I traveled to my destination, my trailer tires rose to 66psi. At my destination at 7800' above sea level, with a temperature of 70 degrees, my final PSI in each tire was 64.

Fast forward a week later, and it's time to go home. Cold pressure was 55psi, still at 7800', and temperature at 62 degrees. I borrowed a compressor and inflated all 4 trailer tires to 64psi.

As I descended the hills, at about 3500' and 95 degrees ambient, tire pressures had risen to 72psi. I still had to descend another 2500' and deal with a 15 degree rise in temperatures. I decided to pull over and dropped the hot pressure to 67psi.

My final pressures at 1000' and 115 degrees was 70psi.

Given the ascent and descents involved, what is the correct method here? Should I be concerned with cold pressures at altitude that will result in hot pressures that increase 20%? Is pulling over at some point and adjusting pressure the correct method? I didn't feel comfortable when I saw pressures reaching almost 75psi, yet everything I've read states that my cold pressure was spot on.

Living in AZ, we will be doing more trips into altitude to escape the heat, so I want to know what others have done when camping in the mountains.

Thank You!

Mr_D 07-16-2018 12:54 AM

Forget changing the pressure due to altitude and temp. Set the pressure when the tires are cold and drive on.

Old-Biscuit 07-16-2018 12:59 AM

Travel day Morning..adjust tire pressures to COLD MAX


Next travel day MORNING........do the same


Do NOT adjust 'on the fly' while in transit

Flarpswitch 07-16-2018 01:37 AM

From sea level to 8,000', the pressure change is less than 4 PSIA. Temperature affects the tire more: 1 PSIA for each 10 Deg change. I measure my tire temps using an infrared temp thermometer. Under-inflated tires will run hotter. My rule of thumb is to add 2 PSI if I am going to be traveling in mile-high country for extended periods. Otherwise, I just air up the tires when cold.

60sumtin 07-20-2018 12:52 PM

A good article on the subject written by a tire engineer: Altitude effect on Tire Pressure.

Searching_Ut 07-20-2018 03:21 PM

We have traveled a lot over the years with altitude varying from sea level to well over 10k. Iíve found there is generally a temperature change involved that is more significant in regards to the affect it has on tire pressure than the affects of the altitude change. I just check my tires in the morning (tpms) and head out if itís where it should be, adjust first if needed which is rare.

Dropthejacks 07-20-2018 08:40 PM

We've had similar issues with heat. Left NC this past Feb heading south, temps were in the upper 20's, tires set at 80 psi. By the time we got into FL, we were hitting temps in the mid 80's, tires were batting around 95psi due to the temp changes. Had to readjust psi the following morning before heading out again for our 2nd leg of the journey.

aether_one 07-20-2018 08:57 PM

Quote:

Originally Posted by Danny5 (Post 4293634)
I've been trying to search for information on proper tire inflation vs. altitude changes.........

As I descended the hills, at about 3500' and 95 degrees ambient, tire pressures had risen to 72psi.

But your tire pressures were following the temperature, not the altitude.


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