Thanks Guys..It never occurred to me to look on the tyre for a working pressure.  It does  say Max Load at 125 psi.  But of course my tractor tyres say Max Load  at 45psi, which doesnt reflect the  9 psi I run in them,  Different situation, I know.

My concern is that , although I think they are a little overloaded, we also have rocks of course and  I thought some "give" in the tyre  is desirable to accomodate  rock deformation.

I've had this unit quite some years anyway,   and i was just  re-visiting the thought as i prepared  for seeding.

  David,  we  had a little over 30 mm rain  around  and after ANZAC Day, and I think it's nearly ready to start  knockdown spraying, and then seeding.