The normal pressure is a function of the angle a and - starting at angle a0 - it increases with decreasing angle, hits a maximum in the shaft layer (or just before) and then declines sharply. The wear picture of rollers and the decreasing comminution effect towards the edges of the rollers are also indicators for an axial pressure decrease.
In the following test results are reported where pressure sensors at l = 0, 19 and 38 mm were used, correspondingly l = 0, 0,19 and 0,38, see picture above. Out of this the peripheral pressure distribution P(a, l = const.) and the axial pressure distribution p(a = const, l) are resulting. Variable parameters were the type of feed material, the graining and the circumferential speed. The appendix of the dissertation of U. Lubjuhn  gives an overview over the test conditions and contains all detailed test results. The number of pressure distribution measurements is shown in table 10 and 11. Additional informations regarding the axial pressure distribution can be taken from the so called stripe tests where
throuput as well as particle size distribution were measured in dependence of the axial coordinate, see also experiment setup.