"Cold" tire pressure.

[kschachn]

I had a Lincoln Navigator with nitrogen filled tires. Total waste of money! Pressure dropped in winter and rose in the summer.

It better, otherwise they are empty.

 

[alarmguy]

"cold" when the ambient air temperature outside is the same as the tire temperature.

Note= if the tires are in the sun one side of the car will not have "cold" tires.

 

[Hermann]

I measure mine in the morning, before the sun hits the car. My definition of cold YMMV

If one side of the Venza get full sun for several hours, the pressures will show about 2-3 psi higher than the shady side on the MID display when cold. My medium quality gauge and MID are within 1 psi.

 

[alarmguy]

^^^ yes

 

[sk_pete]

I had a Lincoln Navigator with nitrogen filled tires. Total waste of money! Pressure dropped in winter and rose in the summer.

Nitrogen in tires is just a marketing gimmick.

ripoff the customers

 

[FZ1]

How many miles/minutes of driving are needed before a tire is no longer considered to be at "cold" temperature. I feel like this is never actually discussed when you buy a new set of tires with respect to longevity. Also if you are just idling down the road, does a tire ever really reach a "normal operating" pressure? How about ambient temperature? Seems like the tire industry deliberately leave this undefined to further their own interests....

Overnight. You pick the morning.

 

[Gimpy1]

NO NO NO all of you are wrong! Your tires must be at absolute zero (-273.15C or -459.67F) before you measure your tire psi. I can't believe you guys didn't know that, pffft measuring tire PSI at ambient temps, AMATEURS

 

[barryh]

NO NO NO all of you are wrong! Your tires must be at absolute zero (-273.15C or -459.67F) before you measure your tire psi. I can't believe you guys didn't know that, pffft measuring tire PSI at ambient temps, AMATEURS

I have a formula written in a spread sheet that calculates the change in pressure with temperature and it does take account of absolute zero as temperature in the gas laws is always in Kelvin. Units of pressure are also absolute rather than gauge so when working in bars in the formula you have to add 1 to the normal gauge pressure.

This example calculates that 8.07 Deg C will produce a 0.1 bar change from 2.0 bar to 2.1 bar (or the other way around)

(-1+273)*(2.1+1)/(2+1)-273 = 8.07 Deg C

 

[Rand]

Well, it's about a balmy 48 degrees here...I've got Nitrogen filled all season touring tires. I idled down the road (100% no throttle) at about 15-20 mph and around the corner all the way to the next street over, then drove about 35 mph for about 1,000 feet straight into the Costco where I topped it off with nitrogen to 33psi, (Just one psi above "cold") before driving to the Big O tires for the first rotate and balance. Total distance to the Costco from my house was 0.8 miles. Sound about right?

I also fill with nitrogen.. the special 78% mix as long as the compressor isnt spitting out water not much difference IMO.

 

[Gimpy1]

ripoff the customers

I agree in passenger tires N2 is a gimmick. In F1 and other top of the world racing it is not. Those cars are pushed to the absolute limit and miniscule changes in anything can mean a loss, but those tires run at very high temps. That would turn passenger tires into liquid. Capri can probably tell us more.

 

[RhondaHonda]

My Corvette says whether the tires are cold, warm, or hot but I’m not sure if that’s an actual measurement or some calculation based on ambient air temperature and the amount driven/air pressure.