Fatigue resistance in filled rubbers is largely dependent on the energy available to propagate a crack, but the influence of the stress concentration is undetermined in elastomeric fatigue. In metals fatigue, a stress concentration is virtually unaltered by cyclic loading. Rubber undergoes large reversible strains and it is argued that rubber components have less severe surface flaws when preloaded than in a stress free state. In fatigue, higher stress levels in the pre-stressed (pre-strained) material are thought to be partially compensated for by improvements in surface finish. It is...