THE STIFFNESS OF AGRICULTURAL TRACTOR TIRES

The dynamic stiffness of rolling agricultural tractor tyres in the radial (or vertical) direction has been measured. The ways in which this characteristic changes with the environment in which the tyre works and with the type and construction of the tyre are described. This information is based on measurements of 17 different tyres ranging in size from a 7.50-18 ribbed tyre to an 18.4R38 traction tyre, and ranging in age from 1 to 16 years. Factors which most affect the apparent radial stiffness of the tyre are the inflation pressure, the tyre size, the age and wear of the tyre and the surface over which it is rolling. A simple method for predicting the stiffness of traction tyres from the tyre size and pressure is suggested.