I have a B7100D and my son has a B6100D. I wanted to give him my ag tires and buy a new set for mine. I knew the fronts were 6-12's on both, but I was surprised to find the rears were different, 8-16's on the B7100 and 7-16's on the B6100. Are the front to rear gear ratios different for the two tractors? They seem so alike otherwise. eserv stated this in one thread "The gear ratio is 1.4664 on The B7100 The tire ratio should be very close to the same with preference to a little front lead." Does anyone know the ratio for the B6100?