Lifetime testing belongs to the product development of rubber parts, especially if these parts are used in safety relevant applications. A methodology, called Rainflow-Filtering, is presented, which can reduce the test time significantly. In this small and not damage relevant load cycles are removed from the load signal and thus, the signal is shortened. The filtering process and the following building of the test signal are explained. The influence of Rainflow-Filtering to the damage caused by a stochastic signal is discussed and it is shown, which time reduction can be achieved. From experiments, the applicability of this method for rubber parts is confirmed.