Abstract: Devices for demonstrating the effect that eccentricities in a tire and rim can have when the combination is rotated having a circular member representing a rim mounted for rotation about a center different from its geometric center and an annular member representing a tire with a varying radial dimension is positioned and retained at a plurality of angular positions on the circle member. An indicator operatively associated with the annular member represents the resulting eccentricity of both members. A similar hand-held device represents that combined eccentricity by conveying vibrations through a handle to the operator's hand.