An aspect is a thrust plate assembly for an air cycle machine. The thrust plate assembly includes an annular body defined by an outer rim and a main bore. The annular body includes a nozzle side and a thrust bearing side. The nozzle side includes a nozzle region proximate the outer rim and a turbine rotor region proximate the main bore, where the outer rim has an outer diameter. The thrust plate assembly also includes a main bore seal installed in the main bore. The main bore seal has an inner diameter, where a ratio of the outer diameter of the outer rim to the inner diameter of the main bore seal is between 3.94 and 3.96.