During the service performance of a friction ring in a continuously variable transmission (CVT) mechanism, the most commonly observed failure mode is fatigue failure. The main purpose of this study is to determine the reason of this failure and to improve the shape of the ring. The ring is modeled by the finite element method (FEM) and also checked by analytical formulas generated for circular rings. The calculations show that high interior stresses are present on the contact surfaces. The shape of the ring is modified to find the optimum shape and dimensions of the ring. By turning a groove inside of the ring, the surface stress is decreased, but the stresses near the groove is increased based on a FEM analysis depending on the groove radii. After analysis and optimization of the groove radius, the dimension R = 1.95 mm is calculated and tested. Fatigue failure is observed to decrease by testing the modified ring. (C) 2000 Elsevier Science B.V. All rights reserved.