I have an older SX 75 John Deere mower. It has a 9hp Kawasaki motor & a 30" cut. This spring I put on all 3 belts new from my JD dealer. Within a month I shredded the blade drive belt. JD wasn't open so got a belt matched @ NAPA. Another month or so & that belt is about shot. What do I look @ for the cause.
JD belts are normally cut at a different angle to off the shelf belts, which will cause it to shred the aftermarket belts. Just make sure that the belt is not rubbing anything that could cut and burn the belt, like belt guide, and use JD belts, or aftermarket direct replacement belts.