exactly..

you need to define your measuring protocol first.. car not driven for X hrs.. standing in garage of temp y degrees.. this will have more impact than the device to measure.

also as long as it is repeatable rather than random.. and you are happy with the result, then 1 or 2psi reading accuracy.. won't change much.

 

I have a digital Halfords one which seems pretty accurate, it tends to read 1 to 1.5psi higher than the petrol station gauges (which I assume to be crap). The only annoying thing about it is it's hard to get a good seal so checking them pressure can result in losing a few PSI trying to get a reading

Mine don't seem to vary much anyway, last time I checked many weeks apart and the pressures hadn't budged at all.

 

Here's a thought. Any even half decent guage is going to be consistent with itself. Therefore, but one, when you're happy with your pressures, record what the dial says, and inflate/deflate to that pressure in the future.

32 is recommended, but you might be happier with different pressure.

 

Chilled's is by far the best method.

All 'standard measurements are at 21.5 centigrade if memory serves and should be soaked at this temperature for 24 hours or greater. Therefore it's largely pointless to have a gauge accurate to the n-th degree.

It's far better to buy a pressure gauge and a depth gauge. As Chilled says a decent gauge will be repeatable and reproduceable. Therefore you just need to get the pressures right and then regularly measure the tread depth across the profile of the tyres. You can then adjust the pressure dependant on how your tyre's are wearing.

The added advantage of this is it shows any alignment issues very early since you'll start to pick up any odd wear patterns