It may depend on which chassis/body combo and what size tyres you have. When I had Peggy (Highwayman) I ran her 15" tyres with 50psi all round which seemed fine.
Spare a Commer Guv?
If I told you I was a pathological liar, would you believe me?
http://66.129.69.181/forum/topic.asp?TOPIC_ID=3934&SearchTerms=tyre,pressure
This was another posting if it helps. This is the sort of thing that if it is for Commers should
, in my opinion, be made a sticky but I don't know how to do it,
Max pressure is just that. It's the max the tyre will take. Doesn't take into account what vehicle they're fitted to.
For each individual vehicle check the handbook (if you're lucky enough to have it still), see what pressure others are using and how they're getting on, check tyre wear, and how it handles and rides.
Don't forget if you load it up with a few hundred weight of heavy camping gear you ought to up it at the rear by a few psi too. 5psi as a very general rule of thumb.