Tyre Pressures

[topless_mx5]

Bit of a boring subject I know.

I've just come back inside after checking the tyre pressures on all of the cars in the household. On average they were about 4-5 psi lower than when I last checked them a couple of months ago (I've been a bit slack, normally do it every 2 or 3 weeks).

Anyway, I assume this is due to the fact the temperature is much lower now so I've pumped them back up.

Is this normal and am I right about the temperature? Does this mean that come Spring time I will need to let some air out, as 30psi in Winter will probably be around 34psi in the Spring (assuming of course no air is lost in between).

[ballscript]

Done a little maths, reckon you'd see about a 5psi drop over about 20°C change in temperature. Using ideal gas law with ballpark numbers.

So seems reasonable.

[cuprabob]

That's why the chavs use Nitrogen innit