Tire Pressure and Temperature, What's the relationship?

Darkbloodmon

Darkbloodmon

Active Member
Joined
Dec 21, 2020
Location
Concord, NC
Question has been on my mind for a few years now, figured a 4x4 forum would have some ideas or consensus so here it goes....

Does a high tire pressure result in better tire cooling; all other variables remaining the same?

Technical context : 265/70/17 is the stock tire size for my 03 5.9 CTD 6MT, Rec. pressure from the data plate is 60psi front 70psi rear, max pressure on the tire is 80psi. I run on the street 74 psi square.
Tires are a 6 ply LT Tire with an A temperature rating. My usual curb weight is 7600Lbs +- 433lbs for the increased fuel tank capacity.

Bonus question: If for any reason I find my self in a situation where I need to drop my tire pressure, how low is to low given the tire max pressure, temp. rating, ply, and or tire intended use?

My front end is more than 1200lbs, and at the pressure I run my front tires still compress the side walls a good bit. Rear is near picture perfect for a tire display.
 
6 ply on a 3/4 ton with 74 lbs in them? I see you like to party... you sure they're not 10 ply?

I run the tires on my HD at 55 psi. They wear fine, don't beat me to death, and I don't spin in wet grass. There's no need to run anywhere near 80 lbs in a Load Range E tire if you're not fully loaded. Even when I grossed 24k with my excavator on my gooseneck trailer, I still ran 55 in the rear tires. Usually not more than a 20 or 30 minute drive though and the tires probably weren't overloaded. Most of the weight was on the trailer.

To answer the question though, it's not that it cools the tire so much as it keeps it from getting too hot to begin with. It's also only rated to carry its maximum load capacity at its maximum inflation pressure for the same reason. Heat is one of the main killers of tires. Extreme example: big rigs need to replace duals as a pair. If one tire is drastically taller than the other, the taller tire will take all of the load, overheat, and blow out if it gets bad enough.

I like to run my tires at whatever pressure lets the whole tread width contact the asphalt. It's different for every vehicle. I could run less in my rear tires, but it works, so whatever. I know your front tires look compressed, but it's just the "radial bulge". Mostly caused by their construction...it's just how they look. I probably wouldn't run any less than 45 or 50 in the front. Wouldn't want it to get squirrelly, it'll definitely ride better though.

Minimum pressure? As long as there's enough air to keep the bead seated and you're not riding on the sidewalls. Dropping air pressure in heavy ass trucks doesn't usually do much. They get stuck just the same.
 
That's why you see OEMs putting nitrogen in the tires. It's an inert gas that isn't sensitive to temperature.
 
Well, that (because people are lazy), and it's dry. Doesn't mess up the sensors with moisture content.
 
Bebop said:
That's why you see OEMs putting nitrogen in the tires. It's an inert gas that isn't sensitive to temperature.
Click to expand...
That's a bs sales gimmick everyone falls for.
Earth atmosphere is 78% Nitrogen.
It is true that nitrogen expands and cotnracts less than some other gasses, but at the pressure used and experienced on street tires it almost indiscernible.

Also, before they pump that nitrogen in there the tire has air in it that isnt pure nitrogen unless the draw a vacuum on it in which case it wont seat on the bead and then atmosphere air will flow in.
The ONLY street beneift to nitrogen fills is most shops dont properly dry their air lines and moisture is hell on a TPMS.
 
The usual benefit is that tire permeation of nitrogen is slower than the other mixed gases in atmospheric air, so the tires lose less pressure with time when inflated with 'only' nitrogen. That's the lazy factor, because "hey look, less maintenance!". That actually makes sense, because most people neglect the crap out of their tire pressure regardless of what they're filled with. Normal solution: Check your f'ing tire pressure regularly, instead of once/twice a year.

Most/all other nitrogen benefits are very small for normal street vehicles and normal use. The better temperature stability of nitrogen is because there isn't a significant amount of water vapor inside the tire; water vapor is mostly what causes the larger pressure swings with carcass temperature than with just nitrogen. Nitrogen still expands with temperature, just like any other gas.
 
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Croatan_Kid said:
6 ply on a 3/4 ton with 74 lbs in them? I see you like to party... you sure they're not 10 ply?

I run the tires on my HD at 55 psi. They wear fine, don't beat me to death, and I don't spin in wet grass. There's no need to run anywhere near 80 lbs in a Load Range E tire if you're not fully loaded. Even when I grossed 24k with my excavator on my gooseneck trailer, I still ran 55 in the rear tires. Usually not more than a 20 or 30 minute drive though and the tires probably weren't overloaded. Most of the weight was on the trailer.

To answer the question though, it's not that it cools the tire so much as it keeps it from getting too hot to begin with. It's also only rated to carry its maximum load capacity at its maximum inflation pressure for the same reason. Heat is one of the main killers of tires. Extreme example: big rigs need to replace duals as a pair. If one tire is drastically taller than the other, the taller tire will take all of the load, overheat, and blow out if it gets bad enough.

I like to run my tires at whatever pressure lets the whole tread width contact the asphalt. It's different for every vehicle. I could run less in my rear tires, but it works, so whatever. I know your front tires look compressed, but it's just the "radial bulge". Mostly caused by their construction...it's just how they look. I probably wouldn't run any less than 45 or 50 in the front. Wouldn't want it to get squirrelly, it'll definitely ride better though.

Minimum pressure? As long as there's enough air to keep the bead seated and you're not riding on the sidewalls. Dropping air pressure in heavy ass trucks doesn't usually do much. They get stuck just the same.
Click to expand...

Defender LTXs 6 ply Highway tire, I'd like to say they were nice but my front end destroyed them (hoping to get wheel bearings and ball joints tomorrow morning). But yes I know it's more than what it needs though I like the pressure to feel the road and vibrations. I'll probably lower it on my next set of tires, She definitely slides out in the rain at that pressure I broke a sway bar link with body roll and a full tank; rear kicked out on a turn in 3rd gear while raining and the return movement sheered it right off.

Thanks for answering the question, do you have any recommendations for a tire inflator? 31" is stock and I don't see myself going higher than 35" in the future. Additionally I keep my pressures high to not frequent a tire shop for air as often till I get a road side compressor. I will note that I don't have any irregular wear from the pressure (bulging in the middle), just the front end shredding them.
 
I worked at a tire shop for a while and got a Blue Point digital tore inflator. I've had it for years. It was a worthwhile investment.
 
Ron said:
That's a bs sales gimmick everyone falls for.
Earth atmosphere is 78% Nitrogen.
It is true that nitrogen expands and contracts less than some other gasses, but at the pressure used and experienced on street tires it almost indiscernible.

Also, before they pump that nitrogen in there the tire has air in it that isnt pure nitrogen unless the draw a vacuum on it in which case it wont seat on the bead and then atmosphere air will flow in.
The ONLY street benefit to nitrogen fills is most shops don't properly dry their air lines and moisture is hell on a TPMS.
Click to expand...

Ding ding ding, we have a winner.

I run my 2016 2500HD (gas) ~55 front/65 rear cold. If I am towing a load with my flat-deck (like my Nissan) I will boost both ends up about 10psi. Gives reasonable ride comfort/traction/wear. Recently the colder average temps required me to add some air to all four corners to make sure it would not trigger the TPMS nannies.

Look at the max weight your tire can handle at 80psi (since it's an LT I am assuming that is the max). I think that your weight estimate on your truck needs adjusting; that thing empty is probably close to 7000# with more than 50% bias on the front when empty. The front axle rating is probably ~4k and the rear ~6k (check the doorjamb sticker).
 
OnlyOneDR said:
Ding ding ding, we have a winner.

I run my 2016 2500HD (gas) ~55 front/65 rear cold. If I am towing a load with my flat-deck (like my Nissan) I will boost both ends up about 10psi. Gives reasonable ride comfort/traction/wear. Recently the colder average temps required me to add some air to all four corners to make sure it would not trigger the TPMS nannies.

Look at the max weight your tire can handle at 80psi (since it's an LT I am assuming that is the max). I think that your weight estimate on your truck needs adjusting; that thing empty is probably close to 7000# with more than 50% bias on the front when empty. The front axle rating is probably ~4k and the rear ~6k (check the doorjamb sticker).
Click to expand...

5200 front and 6K rear, My math was off for the fuel tank weight before it's 372lbs full for my 52g. Not sure where I got the 433lbs from; diesel is roughly 7lbs a gallon.

I tried to upload a pic of the door jam sticker but I kept getting a file upload error, though cold pressure rating from the door jam is 60 front 70 rear, it's not to far off for 74 square or 70.

I'll try to hit a weight scale, just filled up my tank.
 
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