Tires: pressure, aluminum alloy, slow leak

Question
If all 4 tires on a car are inflated (electronic digital pump at a tire store) with the same amount of air and 2-3 months later one or more tires have less air than the others, other than a slow leak, is this normal and what can cause this to happen? Shouldn't they all lose the same exact amount?  Thanks

Answer
Lee,

Tires are not 100% airtight - and there will be differences from tire to tire.  Generally these will be small differences.

But the wheels themselves sometimes leak - and the difference from wheel to wheel can be quite dramatically different.

Further, the seal between the tire and the wheel is also a source of leakage - and this is the most likely source of the difference.

It is not uncommon for aluminum alloy to corrode and if that happens in the area where the tire and wheel touch, a leak could develop.

If the leakage is only 1 or 2 psi a month, then that is considered normal.  Any more than that should be investigated.

So it's a good idea to check the tires monthly and top up if needed.