These calculated minimum lubricant film thicknesses may be considered in the light of typical surface roughness values of the components, namely 0.2µm (R_a) for both cam and follower. The film thickness parameter (or lambda ratio (λ)) - the ratio of the film thickness calculated on the basis of smooth surfaces to the composite surface roughness (R_a) - has become an important qualitative and quantitative parameter for a judgemental decision on the lubrication regime which is operative and the likelihood of surface distress in due course. On the flanks the (λ) value ranges between about 4 and 6.5 for the position and speed range examined. The surfaces are essentially separated and elastohydrodynamic lubrication would be taken to be operative. At the nose, however, the (λ) values for the two cases are about 0.2 and 0.4 suggesting boundary lubrication. Alternatively, one might think of the mode of lubrication at the nose as severe mixed lubrication (ie boundary and elastohydrodynamic effects). This is particularly true when it is borne in mind that, due to elastic distortion of the asperities, the surface roughness within the contact when under load may be substantially less than that measured in the metrology laboratory.