A method for measuring the displacement of a vehicle wheel relative to the frame thereof or relative to a fixed point of reference. The method of manufacturing a high-pressure fuel injection pipe is characterized in that the inner circumferential surface of a metal pipe having a large wall thickness and a small diameter is cleaned using a solvent for dissolving foreign particles comprising an acid, alkali or organic solvent after a final pipe-extending step among steps for manufacturing the metal pipe. A level ratio between the two signals is calculated at each frequency.