ESDU 10015 provides a means of establishing how the decelerating forces acting on an aircraft tyre, when rolling or braking on a dry or precipitate contaminated runway, are determined. The Item describes a semi-empirical model of a flexible tyre, substantiated by test data, that considers the forces due to rolling, slipping or skidding of the tyre, due to the tyre moving through or compressing a contaminant and that due to the frictional interaction between the tyre compound and the runway surface. The model is shown to be dependent upon nice independent variables, namely surface texture depth, contaminant depth, contaminant density, tyre inflation pressure, nominal tyre width, nominal tyre diameter, vertical loading on the tyre, runway surface temperature and ground speed of the aircraft. This Item provides background information of the model summarised in ESDU 05011.