How much do tyres deflate?

[JK2014]

Hey everyone, I'm new to the whole idea of efficient driving, so I kind of don't have a clue. I notice that one of the top tips is to keep tyres properly inflated.

I realise that the only way to keep track of this is to actually check the pressure regularly, but I'll ask out of interest - I drive about 150 miles per week. Is there any way of guessing how much pressure tyres lose through normal use?

[trollbait]

Tires in good condition and properly mounted tend to do a good job of holding their pressure. Outside of a puncture, the only time i need to adjust the pressure is from the seasons and changing outside temperatures.

If there is something up with a tire or wheel that leads to pressure loss, there are too many variables to be able to give a loss rate. My wife's car had a tire that could drop 10psi in 2 weeks, one only a couple of psi in a month, and the other two held fine. Which reminds me that I have to check her tires.

[Jay2TheRescue]

I have a truck that hasn't been driven in 2 years, and the tire pressures are fine. Just depends on the tire.

[bzipitidoo]

I've observed that normally, tires slowly lose pressure over a period of months. Some do hold air better than others-- sometimes I've not checked often enough and found all 4 tires down to 25 psi, sometimes it's 1 tire down to 25 psi while the other 3 were still in the low 30s. Then I pump them all back up to about 45 psi.

Once had a tire that would go flat in 3 days, but it would hold air well enough for a day of driving. Couldn't figure out what was wrong. The programmed idiots at the tire shop couldn't find anything either, and went with their default, which is that it must be the stem. Took the wheel off the car, and then it stayed inflated. We finally figured it out: a little rust on the rims where the bead is.

[Jay2TheRescue]

Had some rust on the bead area on one wheel on my old 74 Chevy pickup. I fixed the problem by putting an innertube in there.