# Tire Pressure



## ED_RN (Jun 25, 2006)

My tires are with a max pressure of 50lbs. That's what I inflate them to. If I start off at home in 70 degree weather and drive in Nevada when 110(degrees not MPH) do I have to worry about the heat raising the tire pressue enough to damage the tire?


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## LarryTheOutback (Jun 15, 2005)

Check out this  article at Tire Rack. It doesn't give a solid answer, but some good hints. One thing it says is "The rule of thumb is for every 10Â° Fahrenheit change in air temperature, your tire's inflation pressure will change by about 1 psi (up with higher temperatures and down with lower)."

If true, that means that you will increase to an equivalent of 54psi cold. Your decision as to whether that is beyond the design limits of the tire.

Ed


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## Sluggo54 (Jun 15, 2005)

ED_RN said:


> My tires are with a max pressure of 50lbs. That's what I inflate them to. If I start off at home in 70 degree weather and drive in Nevada when 110(degrees not MPH) do I have to worry about the heat raising the tire pressue enough to damage the tire?


You'll be fine, Ed. The listed pressures take such heat inflation into account - that's why the instructions always say to check tires cold, and not to let air out of warm tires.

Sluggo


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## MJRey (Jan 21, 2005)

I always run mine at 50 psi cold. You're always supposed to set the pressure when the tire is cold or at least not hot. Since the tire companies always specify a cold pressure and they know the tire is going to heat up I've always assumed that some pressure increase was normal and expected. I've not had any problems with trailers or cars following this line of reasoning but that doesn't mean it's right.


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## CamperAndy (Aug 26, 2004)

Let it ride, there will be no damage.

You should also be aware of checking the pressure on the tires when one side is facing the sun and the other side is shaded. You can easily get a 5 psi difference from side to side.


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## cookie9933 (Feb 26, 2005)

In Chemistry, there are several laws that describe how gasses behave. One of these is the Ideal Gas Law, given as PV=nRT. This states that pressure (P) is directly proportional to temperature (T). However, the temperature scale is Kelvin degrees rather than Farenheit.

This means that a Farenheit difference from 70 degrees to 110 degrees will cause a pressure change of roughly 9 percent assuming that the tire's volume remains constant. Because tires are continually flexing, their volumes are likewise changing. But since this is always the case whenever you are in motion, to keep it simple, volume change need not be considered.

Bottom line: the 50 psi at 70 degrees Farenheit becomes 54.5 psi at 110 degrees Farenheit. Not enough to worry about.

Bill


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## California Jim (Dec 11, 2003)

Aside from that excellent scientific summary, consider the heat that is being generated/created just from the friction of the tire rolling along the road. This temperature alone may surpass the ambient air temperature that the tire is rolling in, thus making it somewhat irrelevant.

Yeah, pump em up


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## Carey (Mar 6, 2012)

cookie9933 said:


> In Chemistry, there are several laws that describe how gasses behave. One of these is the Ideal Gas Law, given as PV=nRT. This states that pressure (P) is directly proportional to temperature (T). However, the temperature scale is Kelvin degrees rather than Farenheit.
> 
> This means that a Farenheit difference from 70 degrees to 110 degrees will cause a pressure change of roughly 9 percent assuming that the tire's volume remains constant. Because tires are continually flexing, their volumes are likewise changing. But since this is always the case whenever you are in motion, to keep it simple, volume change need not be considered.
> 
> ...


Wow! Excellent post..

When towing thru the desert on a 120 degree day, make sure to drive a bit slower... Pavement temps can reach 150-160 degrees.. Over the miles, these high pavement temps will find there way to the tires.. This is very hard on any tire.. I wouldnt worry about the psi even if I done my 50 psi air application at 30-40 degrees and they got to 150 degrees.. This has been taken into account in the R & D lab..

Just drive slower than normal to compensate for the high temps.. THIS is one reason California has a 55 mph speed limit for anyone towing a trailer...

Carey


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