n2cars

My wife's C2 is 4 months old. Has 20" wheels. The dealer delivered the car with tire pressures at Full Load. The fronts were 36 psi and the rears were 44 psi. Today the pressures are 32 psi on the fronts and 38 psi on the rears. Is this amount of air loss normal? My other cars, including Porsches, have not lost this much pressure in this short of time. Should I just fill them back up and not worry about it? As an aside, the car is in the garage but the weather is getting cold here in Colorado. The average temp of the garage never falls below 45 degrees. Thanks for you help.

DNorby

maybe the tires were hot the first time and cold the second? 32 f and 36 rear is what I use losing a half .lb per month is normal

DNorby

excuse me and my stupid laptop. using and then losing

blschaefer1

I'd call this normal. Not much air volume in these tires and colder temps yield lower pressures.

SDaddy

My tires have lost zero pressure in the seven months I have owned my car. I believe the owner's manual goes into some detail about temperature and pressure, i.e. the pressure specifications are indicated for 68F and expect about 1 lb difference for every 10F up or down. I measure before driving so tire temp is equal to ambient.

GSIRM3

Probably temperature related.

stratocaster69

What about Nitrogen filled. Formula one uses it. Is it worth it I wonder?

997s07

Air is over 3/4 nitrogen. But pure nitrogen would do two things, the pressure would not deviate much under temperature changes, and the gas escapement would be minimized as the molecular rubber network wouldn't allow bigger nitrogen molecules to leave the tire (oxygen is smaller and about 16-18% of air).

Archimedes

I'm guessing pressures at delivery were hot pressures and you're now measuring cold. That, plus the big change in ambient temperature, could easily account for this difference.

Noah Fect

So nitrogen isn't subject to PV=nRT?

997s07

The ideal gas law? No. No gas is. But it does follow the ideal gas law more closely than other gases. The ideal gas law has many assumptions that just don't hold true in the real world (e.g. gas molecules have zero volume, they don't interact with each other). So F1 tires use nitrogen to have minimal pressure differences with different temperatures.

drcollie

Only two real reasons for nitrogen fill.

1) Keeps pressure more stabilized throughout temperature ranges

2) Better for storage are oxygen has ozone which degrades the tire from the inside out.

Third Reason: Put money in the dealer's pocket.

WindyCityC2S

I suspect they use Nitrogen so that the pressure vs temperature correlations are more predictable. Compressed air has a lot of other components. So the mathematical models are easier when dealing with one gas over multiple gases.

2001f4s

With the cold in Chicago the last few days 2 out of my 3 cars equipped with TPMS are showing low pressure on startup.

theporscheguy

^^^Same with all my cars. Yes I think it's temp related.