I have an old Amerind MacKissic Mighty Mac Shredder. Two of my four tires are shot, and I am replacing them with new ones. The original tires are ribbed, but I will be replacing the two bad ones with knobby tires. I move this machine around with my BCS735, so there is no power to any of the shredder wheels. The question I have is whether I should put the new knobby tires on the steerable front or the fixed back of the shredder. What are your recommendations, and what is your reasoning behind your recommendations. Thank you.