Hi
Are they reinforced or "C" rated (commercial tyres) if so pressures will be a lot higher(Up to 3.5bar...54Psi) The pressure and weight on the side wall is only for the U.S. market. All tyres car, van, caravan, truck should be inflated to the pressures shown on a load and inflation chart to suit the load being carried assuming the capacity of the tyre is suitable in the first place. As most caravans have the smallest capacity tyre the maker can get away with they are on limit all the time. Upsize when changing so the tyre has a reserve of weight carrying capacity. The previous comment about feeling for temperature and tyres looking soft is naive to say the least and not good advice. Visit a tyre supplier it may avoid a blowout or tread coming off!!!