I recently installed a used JRSC and used a 4 rib belt. It fits fine around the pulley until I started the motor. The belt was beeing eaten up buy the pulley and I ended up with a 3 rib belt rather than a 4. Has anyone used a 4 rib belt and didn't have this problem? Is it because the idler pulley's are not aligned right hence it is guiding the belt off center and into the mercyless hands of the belt eating SC pulley?

 

you might have better luck with this question in FI.