It is dificult finding out the minimum pressures manufacturers allow. Lightweight goods just end up wearing out the centre of the tread. Until the packaging loads changed a couple of years ago the load on a 26 pallet curtainsider weighed about 15cwt and most of that was lightweight pallets. Wear evened out at 125 steer 75 drive and 70/75 (twin/ss) trailer. With axle weights a bit heavier now 3.5/4t the trailers have gone up to 85/90 super single and the drive axle the same. Steer remains as before.