Well, of course it all depends on wheter it's laden or unladen. If you're transporting soil is it wet or dry?Which branch of B & Q was it? And the crucial question when considering this - how long are your arms? On the whole I'd recommend something between 5psi and 100psi (unless the conditions are icy, but I'm sure that goes without saying).
If you had bothered with the Search box on this site youwould know that one oof the regulars, gazzawazza, had already answered this question: "if you open the driver's door and look on the doorpost (locking side) you should see a sticker which tells you the pressures loaded or unloaded." You do know which side of the wheel barrow the driver's door is, don't you?
Gosh, some people are so touchy, you try to ask a reasonable question on the grounds of safety and all you get are two snotty replies... and that mikewith (whoever he is) just can't have any patience... :~)
Gef, it's hasn't got alloys but I can tell you it's a right f***y magnet. You should see the looks I get when I'm cruising the 'hood with the top down low and the system up high.
Oh yeah, I've picked up some stuff in this little baby!!!
Eye eye third eye! Don't know much about wheel barrow tyres. But I'm amazed you asked the question! If it's anything like a car tyre it might have a maximum inflation pressure on it somewhere. If it has you know not to go over that pressure. If not then pump it up to what feels good for the job you are doing. A lower pressure will get slightly more grip, due to more tyre touching the ground. If the tyre is rounder when pumped up and you want to use less effort when pushing it, have more air in the tyre.
Thanks for all the answers guys, lots of laffs, and kalel, thanks for your totally serious answer. The reason I posted the question is coz AB has been swamped with questions about tyre pressures when it would be so much easier for people to look in the manual or handbook. That's why everyone's posted comical replies but you wouldn't have known that if you're new to the site or haven't been online lately. Just type "tyre pressures" into the search box and you'll see what I mean...!
All very informative answers, however, you must take into account the fact that you would be driving on soft, not hard, surfaces, therefore your tyre pressure should be at the lower end of the scale, especially for pansies.