By Roger Marble
I found a chart that covers how to adjust tire pressure when you are inflating tires inside a heated garage (heated to 65° F) when the truck or RV will be moved to a very cold location. I am hoping that when you study the adjustment you will better understand what, if any, adjustment is to be made with your vehicle’s tires under these conditions.
Cold climate pressure correction
Because the air pressure inside a tire will decrease when the vehicle is taken from a warm environment to a cold one, some adjustments may be necessary when adjusting the tire pressures of a vehicle to be operated in very cold temperatures.
These adjustments are only made if the pressures are verified and adjusted inside a heated garage with an air supply that is also at the higher room temperature. (No adjustment necessary if done outside.)
In extreme cases, the following table should be used to help ensure that the operating pressure and deflection of tires are adequate at the outside ambient temperature.
Using the load and pressure charts in the book, determine the appropriate “Recommended Pressure” required for the axle load. Then find the same pressure down the left column of the table [below]. Going across to the relevant outside ambient temperature you will find the corrected inflation pressure to be used.
An example of adjusting tire pressure:
- A log truck in Alaska has a front axle capacity of 12,000 lbs.
- The truck is equipped with 11R24.5XZY®3 LRG tires.
- The recommended pressure for this fitment is 105 psi.
- The truck is parked overnight in a heated garage.
- The outside high forecasted for today is -20° F.
- The tire pressures are checked and adjusted prior to leaving the heated garage.
- According to the chart, the tires should be adjusted to: 128 psi.
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Read more from Roger Marble on his blog at RVtiresafety.net or on RVtravel.com.
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We’re getting ready to leave TN for FL temps going from 30’s to 70’s. Tires require 65 PSI. I’ll start the trip with pressure set for TN temperatures and as we travel south adjust for warmer temperatures as we take 2 1/2 days to make the trip driving 4-5 hrs a day. I’ll check the tires each morning adjusting pressure as needed.
Would have liked to have seen 70, 65, 60, and 55 psi on your chart.
The tires on our Escape 5th wheel are to be run at 55 psi.
Perry, you could make your own chart by simply calculating a 2% pressure change for each change in Ambient of 10°F. Before you do, I suggest you review my blog posts (see the link below)
Here is my question: If the outside air is cold, as in the example of the Alaska Logging truck, and you adjust the tire pressure to 128psi, once you leave the garage, are driving a while (which should heat up the tires?) and then the outside air temperature starts to rise during the day, doesn’t that leave a dangerously high PSI level in your tires?
Said another way:
If you adjust the tires in the early morning when the temperature is low, what happens later when the outside temperature rises?
Often had wondered the same thing, how would one compensate for tires checked on the sunny side of the vehicle to the shaded side on a 90 degree day.
When checking or setting pressure you should do that when the tires are at the prevailing Ambient temperature and not warmed from being driven or in direct sunlight. The above chart is intended for an extreme situation. I have covered the temperature question in detail in my blog posts. https://www.rvtiresafety.net/search?q=NRT I suggest that if you have questions you review those posts.
They will warm up but you really only need to be setting tire pressure once a day, before you start driving and before they are warmed by the sun. Tires are designed to tolerate the increases you will see with your TPMS.
Thank you for the response Roger.
Very helpful info, was not aware of this scenario. Gonna take a snap shot and keep for handy ref guide.