A customer recently had cause to utter curses, when his wheel exploded as he filled the tyre with air.
He had read the Max PSI written on the tyre wall (50 PSI) and hadn't seen the warning witten on the wheels itself that .....
THE MAXIMUM PSI FOR THE PLASTIC HUB IS 30 PSI
We don't recommend using a high pressure air supply to fill the tyres - you are far safer using a foot or hand pump which has a pressure gauge on it.
This applies to the standard blue 6" hubs and Larger 8" hubs.
Please don't over-pressurise the hubs as they are not designed to accept the maximum pressure that the tyres are capable of.