Described herein is a method to evaluate the cleaning performance of brush cleaners by measuring the brush to photoreceptor nip width (115) (e.g. cleaning footprint or contact zone) using a sensor (120). The sensor (120) detects a leading edge (92) and a trailing edge (91) of the brush to photoreceptor nip (115) to determine the nip width measurement which is converted into diagnostic information using a software algorithm or similar mode of conversion. The diagnostic information can be used in a variety of ways such as a diagnostic tool for a technical representative to warn against the end of brush life, to adjust cleaner biases for automatic changes in setup to achieve better cleaning, to predict brush replacement, to correct brush BPI (i.e. brush to photoreceptor interference) for an under or over engaged brush.