Outside Air Temperature

ILH

Well-known member
My wife and I are heading away this weekend for our first camp of the season. While prepping the RV over the last couple of weeks, I started putting the tpms on the valves. It was about 60F when I started - got the driver side wheels done. Pressures were set at 80 psi. Unfortunately it started raining, so I left the other side for this week. This week it is about 72F. Interestingly, when the tpms monitor was turned on, the tires that were filled during the colder weather are about 4 lbs higher than the other side.

Its just physics, but it shows clearly how outside temps can affect your tire pressures.
 

priorguy

Well-known member
I had a Chevy Venture for a work van that would read low tire pressure on a cold morning until I drove 10 mins or so.


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Miltp920

Well-known member
This proves how important checking air pressure each trip, dont take anything for granted. We risk a blow out from under inflated tires if weather cools from last time we checked our tires. Extra pressure seems to be less of an issue than under pressure.
 

danemayer

Well-known member
This proves how important checking air pressure each trip, dont take anything for granted. We risk a blow out from under inflated tires if weather cools from last time we checked our tires. Extra pressure seems to be less of an issue than under pressure.
If you check the tire pressure when it's 70F and tires are not in direct sun, and you haven't been driving for a couple of hours, you should set them to the max cold inflation value that's stamped on the tire sidewall (unless you have individual wheel weights that argue for a lower setting per tire manufacturer inflation charts). For most of us, just go with the max cold inflation value. Usually 80psi on Load Range E tires, and 110psi on Load Range G tires.

If temps are above 70F, you'd set the inflation to 1.5 - 2.0 psi higher for each 10 degrees F. If lower temps, set the inflation lower by 1.5 - 2.0 psi for each 10 degrees F.

So if it's 85 F, and you have LR E tires, you might set the inflation to 82psi instead of 80 psi. If it's 40 F, you'd set them to 75 psi.

With LR E tires, you're closer to the 1.5psi adjustment, and with LR G, closer to the 2.0 per 10 degrees F.

After you start driving, the heat generated by flexing the tire, along with road heat and direct sun, will increase the pressure significantly - sometimes 10 - 20 psi. The only practical way to get the right inflation is to set it before you start driving.


If you use temperature in C, you'll have to do some conversions.
 

Miltp920

Well-known member
Good info. I started at max cold pressure , probably 60 degrees. Saw 10psi increase on the trip. I could have lowered it 1.5 -2psi, since it was under 70 outside. I forgot or did not understand max air pressure was tied to 70 degrees. I will adjust in future. Added this info to my smart phone, since my memory isn't as good as it used to be.
 

JohnD

Moved on to the next thing...
Is it possible that we are over-analyzing this tire pressure thingy???

I'm starting to wonder if maybe...just maybe...all of this tweaking of tire pressures could possibly be the cause of all of the blow outs we keep reading about around here. :confused:

I mean, really, some of the stuff I've read here tells me that I should never pull my camper out of the yard since there is no way that we can keep the tires at it's towable inflated value no matter what the outside temperature is and what speed we may be traveling, or how much weight might happen to be on each tire at any given time...which side of the trailer is the sun shining on and how long has it been shining on those same tires...because all of these things change at a moments notice.

We'd be pulling over every five minutes to check our tire pressures...even with the unreliable TPMS!

Heck...we owned our old trailer for 12 years and it had the same tires on it when we traded it in for our Trail Runner that it had on it when we bought it.

And who knows how old they already were at that point in time?

I never once had a tire issue...I checked the tires before we left on each trip and rarely ever in the 12 years we had that trailer did I ever have to add any air.

As far as I know, the new owner of that trailer still has those same tires on it!

That being said, if I still owned it, I would have replaced those tires last summer...although after all of the tire hooplah around here, I'm scared to death of my 1 1/2 year old BlowMax's with less than 3000 miles on them and will be replacing them soon instead!

Anywayz...

The best we can do is to keep them at the recommended air pressure and enjoy our trip!

Tweaking the tire pressure every time we turn around can't be good for our tires...most especially when they are hot!

Can it...?

Something to ponder.
 

donr827

Well-known member
Sometimes I think we try to over analyze the tire pressures. I am one of them. Sitting here I am thinking at the label on the truck that tells what air pressure to set the tires for at the front and rear axel. Do not think, not 100% sure, that my truck manual mentions anything about adjusting air pressure for temperature changes. Maybe with the ST tires on some trailers might be a case to be more diligent . Don
 

danemayer

Well-known member
You really shouldn't need to tweak tire pressure. Get it set correctly and monitor. If everything is working correctly you probably won't have to add air more than 2 or 3 times per year.

Understanding how ambient temperature affects tire pressure isn't about setting tire pressure precisely every day. But if you see a morning reading that's a bit high or low, you'll understand whether it's due to the temperature. That knowledge lets you make a good decision on whether you need to pull out the air compressor.

And if all this seems too complicated, just inflate your tires to the max cold pressure 2 or 3 times per year and monitor for leaks.
 

whp4262

Well-known member
I would think if temperature fluctuations were that critical then the manufacturers would publish a temperature correction chart and require it to be followed along with a calibrated pressure gage. My Goldwing has a pretty sensitive TPMS and if I take off on a morning a little colder than average my TPMS light will flash. I keep the speed down until the tires warm up and the light goes off, usually takes 2 or 3 miles. If it were that critical I would have to add air going to work and let some out to come home.


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