Tire Pressure increase

[Robert Himbarger]

At a constant speed of 60 mph and outside temperature 90? what should I expect the pressure increase from cold pressure. 07 HR Endeavor 275/80 R22.5 XZA2
Michlin cold set correctly for load

 

[BruceinFL]

One psi for every 10 degrees F above cold inflation temperature. The temps are of the tire, not the OAT.

 

[Larry N.]

One psi for every 10 degrees F above cold inflation temperature.

Keeping in mind that the tire's temp is affected by direct sunshine and road friction, as well as the outside air temp. I've seen tire temps at 125? on one side with 95? on the other side, and this on tires that were the same pressure and temp before hitting the road.

So the 1 for 10 has to account for the actual tire temp, not just ambient.

 

[BinaryBob]

Cold pressure at ambient is all we can benchmark.
I've left the house at 4 below, gone south and arrived at 78 F with a cold psi increase of 8 to 10.
So the 1 psi / 10 degrees is fairly accurate.

 

[Dragginourbedaround]

My tire temps will increase approximately 15 psi as I am driving at 62 mph.  My front tires start out 80 psi cold and will go to 95 psi and my rear tires start out at 90 psi cold and increase to 105 psi driving.

 

[Robert Himbarger]

The tire air temperature ended to be about 100? being a little higher on the Sunnyside lower on The shade the inside duels were higher then the outside duels the pressure on the duels remained the same and the pressure on the fronts stayed Constant. The fronts Cold pressure was 110 and raised to 130 the rear Cold pressure was 105 and raised to 120. Do others find similar results?

 

[Larry N.]

That sounds normal to me, Robert.

 

[Robert Himbarger]

Thanks that was what I was hoping to hear

 

[Utclmjmpr]

Thats why its so important to start out with the correct pressure for your WEIGHT PER TIRE,,even with a 22.5 wheel 110 is probably too high unless you have a VERY heavy coach.>>>Dan  (My 39 foot American Trad. weighs 26750 and the correct pressures are 80 for the four rears and 94 for the steer's )

 

[AStravelers]

The tire air temperature ended to be about 100? being a little higher on the Sunnyside lower on The shade the inside duels were higher then the outside duels the pressure on the duels remained the same and the pressure on the fronts stayed Constant. The fronts Cold pressure was 110 and raised to 130 the rear Cold pressure was 105 and raised to 120. Do others find similar results?

If you don't have a TPMS (Tire Pressure Monitor System) you really need to add that to your tires.  Picking up a nail or screw as you start out in the morning and 2-4 hours later you have a blow out because of the slow leak can be disastrous.  Especially if it is the front tire and causes you to swerve off the road, or worse yet into oncoming traffic. 

Additionally if you will monitor the tire pressure, every so often as you drive, you can see if any one tire starts to have a problem like a slipped belt which causes that single tire to increase in pressure significantly above the other tires. 

And yes going up 20psi in hot weather is normal for tires starting at around 100psi. 

 

[Robert Himbarger]

Reply to Utahclaimjumper my 36 foot endeavor weighs 33,000 pounds and 110 psi Front and 105 psi rear are the correct pressures for the load

 

[Robert Himbarger]

Reply to AStravelers I have a TPMS that's how I was able to get the pressures and temperatures of the tires while in motion on the road

 

[Gary RV_Wizard]

One psi for every 10 degrees F above cold inflation temperature. The temps are of the tire, not the OAT.

NO!  That is not a  correct rule of thumb - it is accurate only for a certain range of tire psi. Roughly those around 60 psi.  It's far to high for a typical car tire, and far too low for a large motorhome tire.

The exact figure is 1.8% of the starting inflation pressure, per every 10 degrees F.  For a rule of thumb (simpler arithmetic) we use 2%, so for Roberts tires, which will typically be inflated to around 100 pis, he can figure 2 psi per 10 degrees (F). If he inflated them "cold" in the morning at 70 degrees and the tire itself reached 130 degrees under the conditions he describes, the increase would be 60/10 x 2 psi - 12 psi.

The ambient 90 degree temp only means that the tire will run hotter because it cannot shed heat as fast. The heat comes from friction with the road surface and tire flexing.  In that large tire size, an increase of 10-15 psi is common under the circumstances Robert cites.