Photography of the real contact area of tyres during motion.

This report describes a new technique of photographing the contact patch of a tyre on a moving vehicle by means of an optical system which enables the real area of contact on either a dry or wet glass surface to be ascertained. Preliminary tests with normal running tyres have established the test procedure necessary to obtain clear and precise photographs at speeds up to 45 mile/h: measurements of the records obtained show substantial reduction in contact length with increased speed.