Available as part of the ESDU Series on Performance. For information on all ESDU validated engineering data please contact us using the details on the preceding page. Modelling for side-force coefficients on aircraft tyre@ is dependent on the sharpness of the micro-texture of the surface over which an unbraked tyre moves. A function of macro-texture depth is introduced. It is shown that this function@ F1@ is distributed like a Beta-distribution and enables the calculation of acceptable values for side-force coefficient for any chosen level of probability.