Tire Pressures Increased

[Redapple]

The big benefit of nitrogen is that the pressure is more stable with heat, meaning it expands much less. It is used in aircraft tires for the stability in rapid temp extremes. Way overkill for automotive use.

[vsheetz]

Oh no, not another nitrogen discussion!... (-:

[JFXG]

Originally Posted by IdahoSRT10

If you want more stable tire pressures under all conditions fill with nitrogen instead if air.

If you operate your vehicle in a place where the temp routinely goes from +90 to -55 in 45 minutes, then N is your friend. Otherwise, no need.

[Ray,IN]

Originally Posted by Ron_H

Tire pressure and temperature are closely interlinked and both will increase as your tires roll down the road.

First off, is 80 lb the correct pressure for your tires? The only way to know the correct pressure is to know the weight at each of the four tire positions and reference the weight/pressure chart for that tire.

Secondly, tire pressure can only be accurately measured when the tire is cold (ambient air temp).

Lastly, how are you measuring the tire temperature? Only TPMS with internal tire sensors can accurately measure temps. Those with external sensors are grossly inaccurate as they have no way of sensing the internal temperature.

Ron those charts DO NOT show the correct tire pressure for the weight; they show the minimum pressure to support that weight, Michelin, Firestone, and Goodyear all agree on that point.
The RMA=Rubber Manufacturers Association says in this pdf, page 55;

"However, never use inflation pressure lower than
specified by the vehicle tire placard, certification
label or owner’s manual"

[Redapple]

I agree with Ray,IN. Never run lower than what is specified on the placard. Mine says 90 for both front and back. With my loading, I run between 100 and 105. For me 90 is under inflated. The pressure will go up as the tire heats up, so always check pressures cold, and NEVER let air out of a tire when hot. Not good.

[Cooperhawk]

We have and believe in the TPMS from TST. This morning I was drinking coffee and preparing for travel tomorrow. I sit in the drivers seat and let the TPMS go through all the tires. I noticed that the tires on the right side were 10 lbs higher than the rest. Also the temps were 20 degrees higher.

Now, on the duals on the right side facing the sun, the outside dual was ten lbs higher than the inside. The sun did it.

Bottom line is that when tires warm up pressure goes up. I know for a fact that all the tires were aired to the same pressure to start with.

Don't let the little things bother you.

[spritz]

Originally Posted by Dutch Star Don

I'm running helium in my tires and I just float down the road!

[Ray,IN]

Originally Posted by Redapple

The big benefit of nitrogen is that the pressure is more stable with heat, meaning it expands much less. It is used in aircraft tires for the stability in rapid temp extremes. Way overkill for automotive use.

ALL gases expand at the same rate = Boyle's Law.
What you think is a difference in expansion rate of the gas, is actually due to commercial nitrogen being totally void of moisture; which does make tire pressures vary less than normal air- which does contain some moisture.

The same effect may be obtained by filtering all moisture out of the air we breathe. The main reason for using nitrogen in airplane tires is, it is inert. That means it cannot contribute to a fire from overheated tires upon landing.

[Mr_D]

Here is what the tire manufacturers say:
The pressure on the sidewall of a Michelin RV tire and many others is not the "Maximum" the tire should ever have (unlike car tires) it is the minimum to support the maximum rated carrying capacity of the tire.

From the Michelin RV Tire Guide:

"If you look at the tire's sidewall, you'll see the maximum load capacity allowed for the size tire and load rating, and the minimum cold air inflation needed to carry the maximum load."

From page 6 of the GoodYear RV Tire and Care Guide:

"How much air is enough?
The proper air inflation for your tires depends on how much your fully loaded RV or trailer weighs. Look at the sidewall of your RV tire and you’ll see the maximum load capacity for the tire size and load rating, as well as the minimum cold air inflation, needed to carry that maximum load."

Inflation Pressure Safety Margin
Toyo Tire does not recommend an “inflate-to-the-load” policy for RV tires. Tires that are inflated to accommodate the vehicle’s actual loads do not have any inflation safety margin. Consequently, even a minor loss of air pressure will cause the tires to be under-inflated and overloaded. Toyo Tire’s policy is to observe (as a minimum) the tire pressure established by the vehicle manufacturer as indicated on the tire information placard. There are multiple reasons why a safety margin
(by inflation) makes sense:
• All tires lose about 1-1.5 PSI per month due to natural permeation of the tire’s internal air pressure through the tire’s rubber membrane.
• In the event of slow air leaks from punctures, an inflation “reserve” may allow detection and repair of the leak prior to reaching a dangerously low inflation level.
• A safety margin is prudent for users who are apathetic regarding tire inflation maintenance.

But then they go ahead and publish a weight/pressure chart allowing lower pressure for RV's!!

From the August 2010 Motorhome Magazine "Tread Carefully" tire article:

The maximum load capacity allowed for the size tire and load rating and the minimum cold air inflation needed to carry that maximum load are located on the tire’s sidewall.

[Tony Lee]

Originally Posted by Redapple

The big benefit of nitrogen is that the pressure is more stable with heat, meaning it expands much less. It is used in aircraft tires for the stability in rapid temp extremes. Way overkill for automotive use.

Normal atmosphere, with or without a bit of water vapour, obeys the gas law (with respect to pressure vs temperature) just the same as any other gas or gas mixture including nitrogen.