We are running 750 rpm on the fan, around 380 on the rotor, We are also running the St John air chaffer. We are running a 1_2 to 3_4 clearnce on the concaves. We are also using the St John design on the rotor, works good in green stem beans. The Gilcrest drive seems to have more power, they also have a different hub ratio that would pobably be better for our big tires.