Pressure and temp ?

[wegone]

Just got back from #2 in our new trailer, great trip, so great we booked it again only longer for next year.

I had to pump up my tires after I brought the trailer home from the lot I purchased it at.
They called out 65 pounds cold.

Before setting out I hooked up my T&P sensor, the pressure was 4 pounds less on all four tires however the cold temperature was cooler than when I pumped them up last time.

I am thinking this is normal, right?

[Gkri]

Yes, pressure changes with temp. (PV=NRT). I don't trust the TPMS sensors for accurate pressure but for pressure and temperature trends. I use a round, bourdon tube type gauge for accurate pressure readings on truck and trailer and adjust about 4 times per year, but do check before each trip.

[wegone]

Originally Posted by Gkri

Yes, pressure changes with temp. (PV=NRT). I don't trust the TPMS sensors for accurate pressure but for pressure and temperature trends. I use a round, bourdon tube type gauge for accurate pressure readings on truck and trailer and adjust about 4 times per year, but do check before each trip.

OK, last trip after I pumped them up, using a handheld digital gauge, the TPMS read 65lbs on all four, as well when I started out.

I did nothing to them, and I don't recall if I took a reading on each tire first, this last trip....

I do know the first time the outside temperature was about 15 degrees warmer at that time, which I'm guessing means I hit 65lbs sooner than if it was say 50 degrees outside, yes?

[sourdough]

Outside temps have an effect on tire temps. Hotter = higher, lower = lower temps. Air them up when they are cool, haven't been on the road, to the indicated pressure. From there realize that as the day gets hot so do the tires. Hot pavement makes it even moreso. When things start cooling down, or you stop driving, the tires cool off. With those increased temps you will see some increase in tire pressure, same with cooler temps. Air them up when they are cool using a good temp gauge. For reference you can then look at your tpms to see where it stands vs a good gauge and just log it in memory. From there just watch the tire temps/pressures, they will vary up and down. You just watch for variances that aren't normal, particularly one tire hotter, lower/higher than the others. From there just cruise on down the road....

[wegone]

Thanks..... I was leaning that way, just asking for some affirmation

[Gkri]

Originally Posted by Island Eddie

Thanks..... I was leaning that way, just asking for some affirmation

using a few rough assumptions for volume of air, a 20 degree temp swing calculates to about 3 psi difference. With some room for error, I'd say what you saw is reasonable.

[wiredgeorge]

Suggestion. Many threads along this line; even some recently. Fill tire to MAX PSI indicated on sidewall when cold. Temps rise from both turning on the road and ambient temps and I suspect this was taken into account by the tire engineers. Sometimes temps go from about 80 PSI (LRE) to 90-95F and this is normal. Don't overthink it.