The minimum pressures for 3.25 X 19 tyres are 18-lbs. front and 24-lbs. rear. and are sufficient for a solo rider of average weight.
These recommended inflation pressures are based on a rider's weight of 170-lb. If the rider’s weight exceeds 170-lb. increase tyre pressure as follows :
Front tyre: Add 1-lb. per sq. in. for every 28-lb. increase in weight above 170-lb.
Rear tyre: Add 1-lb. per sq. in. for every 14-lb. increase in weight above 170-lb.
If additional load is carried in the form of a pillion passenger or luggage the actual load bearing upon each tyre should be determined and the pressure increased in accordance with the Manufacturer's Load and Pressure Schedule.