A discussion of the method used and the results of a trial to assess the feasibility of using vibration and stress wave analysis for condition monitoring of the C21xx rail grinding fleet. The fleet consists of three trains, each comprised of two control cars, one fluids car and four grinding cars. The primary objective of the trial was to establish a method of condition-based assessment for the control car traction motor suspension tube assemblies. The secondary objective was to assess the value of using vibration and stress wave data to monitor the condition of other bearings and rotating elements. The results from the trial have identified a likely means of detecting worn suspension tube assemblies with the bogies in situ, and have also identified very early damage on the outer races of two axle bearings. Further testing is planned to corroborate the data obtained from this first study and to assess the condition of the control cars in the remainder of the fleet. (5 pages)