Tire pressure (temperature) increase while driving

[WoodIsGood]

What is considered an excessive temperature for tires? If I set my tire pressure to 5psi higher than the manufacturer's recommendation, when driving 65mph on a hot day (100+*) the pressure of the rear tires will increase by as much as 30psi (go from 85 to 115psi). At 10 degrees per 2psi increase that's a 150 degree increase in internal tire temperature. Starting at 75* the tires will reach 225* internally! This is true with both the original Goodyear G670RV and new Michelin XRV tires in size 245/70R19.5-F. This seems excessive to me, so I end up running the tires at the max recommended pressure (95psi, or 15psi higher than the chart recommends). This cuts the pressure increase while driving in half, but results in a harsher ride.

I've weighed by coach several times over the years on various truck scales (rear axle always less than 13,000 lbs. with less than 200 lbs. difference side-to-side). I've checked my pressure gauge against 5 other gauges and all were within 1psi of each other. I use a TST TPMS system (interestingly all 10 of the sensors read 3psi lower than all of my gauges at all pressures from 35psi to 115psi.).

Is a 30psi (and corresponding 150*) increase normal and I'm worrying about nothing? The front tires never increase more than 15psi.

[tropical36]

JimXFarmer wrote:

tropical36 wrote:

JimXFarmer wrote:
I always run near the maximum tire psi as written on the sidewall . My tires run cooler which tells me that I will have less tire problems . All the tread on my tires is in FULL contact with the road as I have confirmed this visually .I get extremely long miles out of my tires that wear very evenly . This tells me the tires "like" the way I treat them with max pressure in them . Sure the ride suffers .
I'm hunkered down now and waiting in the bunker for the inevitable "incoming".......:)

LOL.......You haven't said where that might be according to your actual weight and one could that you're very close to where you should be, anyway.

Actually , when I was towing a 5th wheel or my TT , I was 15 to 30 lbs above the "recommended" pressure by weight .

Certainly better than running 15 - 30 lbs low, that's for sure.
So many don't weigh all four corners and then want to be exact according to the inflation chart with any ambient temp. that it might be, when inflating. So again, I always add a cushion for all the variables, so that I'm always a bit high, if anything and not about to be constantly airing up during our travels.

[wolfe10]

And, here I thought physics applied to everyone. Silly me.

[ArchHoagland]

wolfe10 wrote:

ArchHoagland wrote:
WoodIsGood....I have the solution everyone has overlooked...

You need to fill your tires with Nitrogen!!!

As opposed to DRY air?

WHY??

Threw that in because the nitrogen lovers all claim it will make your tires run cooler.

[wolfe10]

ArchHoagland wrote:
WoodIsGood....I have the solution everyone has overlooked...

You need to fill your tires with Nitrogen!!!

As opposed to DRY air?

WHY??

[ArchHoagland]

WoodIsGood....I have the solution everyone has overlooked...

You need to fill your tires with Nitrogen!!!

[JimXFarmer]

tropical36 wrote:

JimXFarmer wrote:
I always run near the maximum tire psi as written on the sidewall . My tires run cooler which tells me that I will have less tire problems . All the tread on my tires is in FULL contact with the road as I have confirmed this visually .I get extremely long miles out of my tires that wear very evenly . This tells me the tires "like" the way I treat them with max pressure in them . Sure the ride suffers .
I'm hunkered down now and waiting in the bunker for the inevitable "incoming".......:)

LOL.......You haven't said where that might be according to your actual weight and one could that you're very close to where you should be, anyway.

Actually , when I was towing a 5th wheel or my TT , I was 15 to 30 lbs above the "recommended" pressure by weight .

[tropical36]

JimXFarmer wrote:
I always run near the maximum tire psi as written on the sidewall . My tires run cooler which tells me that I will have less tire problems . All the tread on my tires is in FULL contact with the road as I have confirmed this visually .I get extremely long miles out of my tires that wear very evenly . This tells me the tires "like" the way I treat them with max pressure in them . Sure the ride suffers .
I'm hunkered down now and waiting in the bunker for the inevitable "incoming".......:)

LOL.......You haven't said where that might be according to your actual weight and one could that you're very close to where you should be, anyway.

[JimXFarmer]

I always run near the maximum tire psi as written on the sidewall . My tires run cooler which tells me that I will have less tire problems . All the tread on my tires is in FULL contact with the road as I have confirmed this visually .I get extremely long miles out of my tires that wear very evenly . This tells me the tires "like" the way I treat them with max pressure in them . Sure the ride suffers .
I'm hunkered down now and waiting in the bunker for the inevitable "incoming".......:)

[down_home]

I check our tires and wheel bearings with a laser aimed temp gun.
The tires go up about 10-15 on ours most or all of the time.
I check them when we fuel up or just stop for a while.
The right inner tire nearer exhaust is about five degrees warmer, than the rest..
I don't remember if it was especially hot some of the time or not.
Just considering sometimes, If I had the energy, about a scoop somewhere directing air between the two drive tires per side. Might be disadvantage, in Az, when temps are 115 or so.

[tropical36]

rgatijnet1 wrote:
The real danger with OVER-inflation is that the design footprint of the tire will be smaller and this can dangerously affect your braking and traction on dry or wet pavement.

This is very true, as well, but it would take some over inflation and like a lot of it.

[rgatijnet1]

The real danger with OVER-inflation is that the design footprint of the tire will be smaller and this can dangerously affect your braking and traction on dry or wet pavement.

[tropical36]

WoodIsGood wrote:
What is considered an excessive temperature for tires? If I set my tire pressure to 5psi higher than the manufacturer's recommendation, when driving 65mph on a hot day (100+*) the pressure of the rear tires will increase by as much as 30psi (go from 85 to 115psi). At 10 degrees per 2psi increase that's a 150 degree increase in internal tire temperature. Starting at 75* the tires will reach 225* internally! This is true with both the original Goodyear G670RV and new Michelin XRV tires in size 245/70R19.5-F. This seems excessive to me, so I end up running the tires at the max recommended pressure (95psi, or 15psi higher than the chart recommends). This cuts the pressure increase while driving in half, but results in a harsher ride.

I've weighed by coach several times over the years on various truck scales (rear axle always less than 13,000 lbs. with less than 200 lbs. difference side-to-side). I've checked my pressure gauge against 5 other gauges and all were within 1psi of each other. I use a TST TPMS system (interestingly all 10 of the sensors read 3psi lower than all of my gauges at all pressures from 35psi to 115psi.).

Is a 30psi (and corresponding 150*) increase normal and I'm worrying about nothing? The front tires never increase more than 15psi.

Story short, always add a cushion of air for all the variables, no matter what the ambient and I've always added 10 - 15psi over the inflation chart and especially since I only weigh the axles and not all four corners. 5% is usually what's recommended, but don't feel that it's enough and again for all the variables over a long trip. Forget about the pressure increase with heat from the road and not a factor. Unless of course, you've filled the tires to max rating and have exceeded the wheel's rating as well. Even then, I doubt if you'd suffer any immediate damage. Maybe a real rough ride and a bad wear pattern over time.
The real danger, IMO, is to run under-inflated and this will happen if aired up exactly and according to the inflation chart.
Most likely the cause of a lot of blowouts.

[rgatijnet1]

If your TPMS sensors for the rear duals are hooked to valve extenders and out in the air flow, I'm not sure how accurate the temperature readings are.

[jadatis]

What is important for giving no damage to tires, is that not any part of rubber of tires goes over a sertain temperature.
The inside tire temperature shal be in line with the temperature of rubber. Not totally but asume it is for sakes of simplicity.
Lets asume that when inside tire temp is 160 degr F. that then the hottest part of rubber wont reacht a temp at wich it hardens ireversible.

Then when filled AT 50 psi at 65 degr F , it will be at 160 degr F 61.7 psi. 61.7/50=1.234 so rise of 23.4%
Filled at 110 psi at 65 degr F it will rise to 132.6 psi at 160 degr F .
132.6/110= 1,2055 so rise of 20.55%
lower pressure used in normal car tires even gives more % rising when going from 65 to 160 degr F .

Mayby this is why these high percentages are given officially , because those count for pressures of 35 psi to give the tire inside a temp of that 160 degr F.

This 160 degr F is my estimation so dont see it as an exact number, only to prove the different percentages for filed cold pressure.

And ofcource its much more complicated proces. when higher ambiënt temp cooling down of tire is worse but then cold pressure is also higher wich gives lesser deflection so lesser heatproduction.

Better is to give the tire lesser deflection then the critical border sp tire inside wont reach that 160 degr F .
But to high pressure gives discomfort and bad gripp.

I determined that when pressure is the right balance so with some reserve, that then when ambiënt temp is 65 degr F, and driving about 50m/h , the tire inside will reach a temp of about 110/115 degr F.
And when you then calculate the pressure rising in percentages, it will be about 10 to 11% depending on hight of filled cold pressure.

So also my conclusion is that 10/11% is the goal when driving 50m/h.
Then you still have acceptable comfort and gripp.

An ST tire is calculated in maximum load for the AT-pressure for speed of 65m/h.
So using that given maximum load when calculating needed pressure, the tire has more deflection then an LT tire wich is calculated for 99m/h.
By that more deflection more heatproduction at the same speed, so hotter inside tire temp.wich gives higher percentage of pressure rise.
But also for an ST tire its better , the inside tire only reaches that
110/115 degr F when driving 50m/h . so rubber also stays way below the
critical temp, and then comfort and gripp yust as acceptable as the comparing LT tire.