If everything is in line and the belt is developing cracks from the inner radius of the belt to the outer backing before breaking, a heavy flywheel on the wobble box pulley may fix your problems. Belt breaks of this nature are caused by rapid belt vibration which in turn are created by the rapid changes in wobble box rpm's due to heavy oscillating knife loads. See Hyper Mods _ Misc Rotary Mods _ Heddy's Hyper Mods. The heavy flywheel smooths out the wobble box drive and in our experience gives about 4 or 5 times the belt life as well as much better knife performance and life. Hope this helps.