  The line-of-sight velocity dispersion profile of galaxy clusters exhibits a
"kink" corresponding to the spatial extent of orbiting galaxies. Because the
spatial extent of a cluster is correlated with the amplitude of the velocity
dispersion profile, we can utilise this feature as a gravity-calibrated
standard ruler. Specifically, the amplitude of the velocity dispersion data
allows us to infer the physical cluster size. Consequently, observations of the
angular scale of the "kink" in the profile can be translated into a distance
measurement to the cluster. Assuming the relation between cluster radius and
cluster velocity dispersion can be calibrated from simulations, we forecast
that with existing data from the Sloan Digital Sky Survey (SDSS) we will be
able to measure the Hubble constant with $3\%$ precision. Implementing our
method with data from the Dark Energy Spectroscopic Instrument (DESI) will
result in a $1.3\%$ measurement of the Hubble constant. Adding cosmological
supernova data improves the uncertainty of the DESI measurement to $0.7\%$.
