Tire PSI - Cold vs Hot

[Ray,IN]

ST = special trailer tires should always be inflated to sidewalll listed maximum tire pressure to better withstand the extreme sidewall stresss involved, and limit trailer sway caused by flexing sidewalls.

Originally Posted by No1Hunter

I suppose you could look around and find someplace that has 100% nitrogen. My tires came with nitrogen but currently have a mixture (mostly nitrogen). Keep in mind, good old "air" is roughly 78% nitrogen, 21% oxygen and 1% other gases.

Which gas is inside a tire is immaterial, according to Boyles Ideal Gas Law all gasses expand at the same rate.
What makes the difference is moisture, which expands at a different rate. Dry air and nitrogen expand at the same rate for all practical purposes.
Plus, it's impossible to fill a tire with 100% nitrogen unless someone can figure out how to pull a vacuum inside a tire first without breaking the bead seal.

[jadatis]

I made a pressure/temperature calculator, wich also gives for if enaugh water in tire to go over to gas. I think I am the first in that.

If you want to play with it, mail me at my hotmail. com adres with username jadatis, and I send it back in return.

A way to get almost 100% nitrogen in tire, is to fill from a bottle nitrogen, then dropp thevpresdure by letting out air... gascompound, and fill again, in a few cycles.
But what is the use, with water in tire, the pressure rises more, but the tire inside gascompound stays cooler, and with that the tire-material, what pressure advice is all done for.

A 80 PSI filled E-load tire, can rise 20% even so to 96 psi warm, but never bleed down to 80 psi then, otherwise temperature rises even more, and overheating of tire material is fact.
That is only allowed ZERO times in tires use.

[No1Hunter]

Originally Posted by Ray,IN

ST = special trailer tires should always be inflated to sidewalll listed maximum tire pressure to better withstand the extreme sidewall stresss involved, and limit trailer sway caused by flexing sidewalls.




Which gas is inside a tire is immaterial, according to Boyles Ideal Gas Law all gasses expand at the same rate.
What makes the difference is moisture, which expands at a different rate. Dry air and nitrogen expand at the same rate for all practical purposes.
Plus, it's impossible to fill a tire with 100% nitrogen unless someone can figure out how to pull a vacuum inside a tire first without breaking the bead seal.

It's not the amount of expansion but air loss.

"All tires lose some pressure over time from the gasses within them permeating through the tire rubber. Nitrogen does this about 40 percent slower than regular air, according to Chemical & Engineering News, and this results in more stable tire pressures over a longer period of time. Oxygen also reacts with the tire rubber as it permeates through it, which leads to a thermo-oxidative process that degrades rubber over time."

[Lette]

Originally Posted by No1Hunter

So, are these Michelin like kind replacement (16 ply) of what was originally on it or an upgrade? Personally, I would go with what the tire manufacture states.

They are replacements but a different manufacturer. I went with Michelins and I do see an improved ride.

Damned if I don't follow one of these manufacturers - Winnebago's 82 PSI cold ...if tire blows... well finger pointing begins....Michelins 120 PSI cold...:-)

Just ordered the TST 770...so ill have some protection....

[No1Hunter]

Originally Posted by Lette

They are replacements but a different manufacturer. I went with Michelins and I do see an improved ride.

Damned if I don't follow one of these manufacturers - Winnebago's 82 PSI cold ...if tire blows... well finger pointing begins....Michelins 120 PSI cold...:-)

Just ordered the TST 770...so ill have some protection....

Yes, I understand they are a different manufacture but are the spec's different, ply rating, speed rating, etc???? That matters much more than manufacture.

Also, do you remember the tire PSI recommendation on your old tire sidewall? The tires on my TT PSI recommendation matches the TT's sticker.

[Lette]

Originally Posted by No1Hunter

Yes, I understand they are a different manufacture but are the spec's different, ply rating, speed rating, etc???? That matters much more than manufacture.

Also, do you remember the tire PSI recommendation on your old tire sidewall? The tires on my TT PSI recommendation matches the TT's sticker.

The original tires for this Winnebago Vista 31BE were Goodyear 245/70R19.5 G670 [/B][/B][/B]and I believe the PSI rating was 110, speed rating 75, not sure of the ply rating..... When I picked those up from the dealer they were BELOW the 82 PSI. Actually at 75PSI.

Greatly appreciate the guidance!!!

[No1Hunter]

Goodyear 245/70R19.5 G670

I would guess they are "G" rated, which I believe are 14 ply tires. So, you have gone up a little. With that said, I have E rated DuraTractires on my 2000 4runner (my trailhead rig), which originally came with "C" rated tires. I run them underinflated but I am not carrying any weight. They they do howl at certain speeds!!!

Generally, the vehicle manufacture specifies the PSI for the tires they recommend at the gross vehicle weight rating. That is how my Ram 3500 hundred is, and I do not run the tires at max pressure except when towing or hauling.