Tire Loosing Air

[Huw Powell]

What Louis-Alain said.  It works in English, too ;)

On 1/23/2011 11:50 AM, Andrée-Anne Bourgeois wrote:
> Not that much for sure... In fact, you have it almost the opposite.
>
> The formula for perfect gases is (in French) : PV=nRT
>
> P is pressure in kPa
> V is volume in liter
> n is the quantity of gas in mole
> R is the perfect gases constant
> T is temperature in Kelvin
>
> So, for a fixed volume and quantity of gases, pressure change is directly
> proportional to temperature change (temps are evaluated in absolute Kelvin
> only).
>
> Then, if the temp drops by 10F between 68F (293K) and 58F (288K) (that would
> be about 5 Kelvin, more or less), that would lead to a drop in pressure of
> about 1% (293/288).
>
> So, if you filled your tires in October at 50F (283K) and now temp is 0F
> (255K), pressure would drop by 10% (255/283= 0.90).
>
> On a car with 32 psi, that's a loss of 3 psi.
>
>
> So a crude rule of thumb could be 3 psi per 50F or 1 psi per 15F.
>
> Louis-Alain
>
>
>
> -----Message d'origine-----
>
> Isn't there a formula, for every degree below freezing, that a tire looses
> 10 psi?
>
>
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-- 
Huw Powell

http://www.humanspeakers.com/audi

http://www.humanthoughts.org/