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Cold Weather Tire Inflation/Pressure

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Is there an English version of tire pressure guides?  I don't mean written in English but understood in English.  Definitely opening the door for criticism here.

According to many guides (manufacturer or the many forums), tire pressure is lessen by 1-2 lbs for every 10 degrees below ambient temperature.  Also, you should check your tires cold, not after driving any distance over a mile.  Then they discuss the increase in pressure as the tire heats when driving along with pressure increase as the temperature rises as the day warms up.  What is not said is if you check your tire pressure before you start driving for the day and it's about 33-35 degrees outside and your tire pressure is 100 and by weight should be 115, do you add air to get to exactly 115 or not.  Am I missing something? Probably.

 

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My understanding is that yes, you do air up to 115 psi if that is what is required by weight. The tires will heat up as you drive and as the day warms, but those pressure increases are expected and accounted for. Driving with low tire pressure is the problem to avoid, not the other way around. 

If I know that I aired up when it was very cold, and the weather warms considerably in subsequent days I'll eventually  let some air out on a subsequent morning. But if the temps continue to be up and down I'll leave the "cold" pressure alone until the temperatures change for a longer period of time. That is to say that I don't worry about letting out a few psi one morning, only to have to replace it the next. 

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mpt....you are gnat-ass on the money. I agree 100%. I'll add that having the sun shining on the tires when cold prior to driving sometimes with add a pound or 2 to the reading. No big deal, just need to be aware of it. 

Going up in altitude raises tire pressure too. If you going up for a day or two no big deal, to stay up for awhile adjust the pressure down. And don't forget that bicycle on the back. Those tires don't have much volume and the pressure goes up real quick when going up in altitude. And what about that air massage??? OK, I'll quit know. You got the point!     

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I subscribe to the KISS principle (Keep It Simple Stupid). 

I set my tire pressure when the tires are about 65-75 degrees ambient temperature, not having driven and no sun on the tires.  I determine the proper pressure by use the weight from weighting the vehicle, using the tire mfg pressure to weight guide and then add about 10% for a buffer, as long as the 10% doesn't go over the max pressure on the sidewall of the tire. 

From that point on I use my TPMS to monitor the pressure.  As long as all the tires, inflated to the same pressure, stay the same I don't adjust the pressure for very cold mornings or warm mornings.  Both your front tires and all your rear tires should be about the same pressure, set for the weight on the heaviest side of the RV.  I do take into account, when driving, that the inside dually will be hotter than the outside and therefore a few pounds higher in air pressure. 

Again going by the KISS principle I don't add pressure when the ambient temp is 20 degrees in the morning.  Just like not reducing pressure with afternoon temps at 100 degrees, I figure the tire is designed to handle the difference in ambient temperature.

Note, I have never seen any written documentation from a tire mfg that if you have the proper "cold" pressure in the morning at 65 degrees and you are driving in the afternoon with the ambient temp at 100 degrees that you need to reduce the pressure for the afternoon heat.

Note that if your normal cold pressure, in the morning at 65 degrees, is 100PSI then in the afternoon with 100 degrees ambient temp, you are driving at 60mph, the pressure will increase significantly.  Possibly to 115PSI to 120PSI.   Again as long as all the tires relative to each other are about the same I don't worry about it.  If any one is out of line, I stop and investigate to see if there is a problem.

Edited by Al F

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Al pretty much covered it.  Recently getting a new coach and fitting my TPMS on 12 tires instead of 6, I am still working through this.

The first step is to weigh your "loaded for travel" coach.  You can go to almost any Love's, Pilot, Flying J, or other truck stop.  A trip across their scales will run you somewhere between $9.00 and $11.00.  

Look up your tires on the manufacturers chart.  Pay special attention to the listings determining if they are mounted as duals or singles, because it makes a big difference in psi settings.

In the morning before the sun starts heating up one or more tires, and maybe when the temp is between 60 and 75 degrees, air all the tires to where they are suppose to be.  Check them daily.  This is where a good TPMS comes into play.  I turn mine on every couple of days while camped just to check my tires.  Of course while traveling it stays on all the time.

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