newsomer
Seven Miles South of the Cheddar Curtain
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Is the amount tire pressure will increase from cold to rolling temperature important enough to consider when topping off the pressure at the start of a towing session?
For example, if the outside temperature is around 75? and the trailer has been sitting do you fill the tires to the max pressure or to a lower percentage to allow for the increase caused by road friction?
In our case we have a new trailer with the infamous Chinese tires that indicate a max pressure of 50 lbs.
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skipnchar
Topeka Kansas USA
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Tire companies are smart enough to KNOW that temps change and pressure builds up. Don't overthink the problem and just check your tires before each days travel, before they're driven on and inflate to the maximum stamped on the sidewall. If you over think the problem you'd find yourself stopping at every curve in the highway because the sun is hitting at a different angle and your tire pressure changed.
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flhtci-rider
Montreal, Canada
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tires are always inflated when cold. The amountof increase due to rolling heat is taken into cosideration by the engineers.
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Turbo Diesel Dude
Green Mountain, NC
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As the others said.JMHO
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wolfe10
Texas
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Good answers.
COLD is at ambient temperature that day before driving.
If ambient temperature drops 40 degrees (wishing HARD for that right now), you will need to add air.
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newsomer
Seven Miles South of the Cheddar Curtain
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Thank you for the quick replies.
Overthinking, I've only had that problem for 55 years.
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tvman44
Southwest Louisiana
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wolfe10 wrote:Good answers.
COLD is at ambient temperature that day before driving.
If ambient temperature drops 40 degrees (wishing HARD for that right now), you will need to add air.
Agree
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Golden_HVAC
Fulltime, CA, USA
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Hi,
Lets say that your maximum pressure that you want in the tires is 70 PSI cold. You check it at the campground and see 55 PSI cold, then drive to a nearby gas station and it now reads 62 PSI warm. You still should add 15 PSI to the tires, because 7 PSI is due to the tire being warm.
The tires can actually handle a lot more pressure than the cold rating. For instance a typical 3/4 ton truck tire says minimum pressure is 80 PSI when the maximum load is on the tire. The maximum cold inflation pressure is 10 PSI over the minimum pressure and you might measure the tire pressure at 8-12 PSI when the tire is hot and you are traveling at 55 - 60.
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Old & Slow
Texas
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Golden_HVAC wrote:Hi,
Lets say that your maximum pressure that you want in the tires is 70 PSI cold. You check it at the campground and see 55 PSI cold, then drive to a nearby gas station and it now reads 62 PSI warm. You still should add 15 PSI to the tires, because 7 PSI is due to the tire being warm.
The tires can actually handle a lot more pressure than the cold rating. For instance a typical 3/4 ton truck tire says minimum pressure is 80 PSI when the maximum load is on the tire. The maximum cold inflation pressure is 10 PSI over the minimum pressure and you might measure the tire pressure at 8-12 PSI when the tire is hot and you are traveling at 55 - 60.
Fred.
well, this is all interesting. i'm 74 and needed this info' at age 15. however, it's hard to know what the true cold pressure would be if you happen to check tires when hot and the question is 'do i need to add or reduce air pressure'?? i would cross AZ in summer and reduce air pressure if checked at 3 pm. ???
floyd
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Oldfordman
Marysville, WA
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Several years ago, before I retired from a Tire Company I was heading a program to market a Tire Pressure Monitoring System that could be added to Cars, Trucks, RV/s, etc. While doing so I uncovered an obscure parameter that Engineers use while designing and testing tires. It is the actual "Temperature" they consider when formulating a Cold Inflation Pressure. It is 64 Degrees Farenheit.
When a tire is inflated to its design Cold Inflation Pressure, knowing that the pressure will increase/decrease with temperature, these TPMS devices calculate the "Required Pressure" for a given temperature. Otherwise a tire loosing air would heat up, show an increase in pressure, and fail to give warning before the tire failed.
As a rule of thumb, a tire will increase one pound in pressure for each 10 degree increase in temperature. Using this "rule", a trailer tire that measures 110 degrees after running down the road should read 55 PSI if it was inflated to the recommended 50 PSI at 64
degrees F.
I don't have a monitor on my trailer tires but I use the above "rule", along with an Infra Red Thermometer, to set the pressures on my tires. If I start out with an ambient temp (same as tire temp if I hadn't driven yet) of 55 degrees a pressure of 49 lbs is OK. If the Temp is lower, say 30 degrees, a "Cold Inflation Pressure" of 46-47 lbs is adequate.
If you follow the above it is far better than "SWAG"ing (taking a "silly wild a$$ guess" on pressures. The tire will be inflated just like the design/test engineer expected it would over a wide range of "ambient" temperatures.
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