Abstract: A method of determining the inflation pressure of one or more pneumatic tires on a moving vehicle having a plurality of n wheels fitted with tires by performing a set-up procedure comprising, for a range of tire inflation set-up procedure comprising, for a range of tire inflation pressures including all the vehicle tires at their scheduled inflation pressure and combinations of one or more tires at a range of pressures below their scheduled and for a range of vehicle speeds and driving conditions such as accelerating, braking, straight-ahead driving and cornering, deriving for each of the wheels a speed value Cn proportion to the wheel angular velocity, determining and saving the relationship of the set of set-up speed values to each related tire pressure, and subsequently in normal driving monitoring at intervals of time the wheel speed signals of the wheels on the vehicle, deriving an equivalent set of normal driving speed values based on these monitored wheel speed signals, obtaining the associated tire in