Depending on what bearing you use, the shims or spacers may or may not be needed. All we are doing is taking up the space so that the hydraulic throwout bearing does not over-travel and break. With our measurements, 2.875 – 2.625 = 0.25 gap. The manufacturer recommended a 0.150-200 gap between the bearing and pressure plate. We added .075 of shims to get an ideal gap of 0.175.