How much of a difference will 5 more teeth on the back make in regards to rpm at 60mph? My rear pulley came apart and shredded my my belt. Im having a hard time finding a 65 tooth that I like. Also, how many teeth will I need on the belt if I go to a 70 tooth? I remember in the sportbike world it was 1 down in the front equals 3 up in the back. Not sure if that applies to our application.