The design principles and the performance of hydrostatically loaded wear (end) plates in three high-pressure external gear pumps were examined experimentally while the pumps were running under typical operating conditions. The film thicknesses (clearances) between the gears and end closures (plates) in three different designs of floating plate gear pump were measured. It was found that at high delivery pressures all the plates were heavily tilted relative to the gears. The plates appeared to be tilted so that they occupied the total available end clearances in the units. (C) 1997 Elsevier Science S.A.