Those do look a little small in diameter, there is some tolerance, but as you change the outside tire diameter, you change the tractor ground speed, larger=faster. I can see where engine clearance could be an issue with those. Another option to improve traction is to add weight. I can add about 80 lbs of barbell weights to the wheels, and can add more to the engine if needed. I also have foam filled tires that add another 40 lbs/set, and if I get really wild, I have another set to make duals, plus I filled the 6" wheel extenders with lead for another 16 lbs. Don't need it often, but the wide duals help when mowing steep areas. I have pulled the hubs to work on the brakes, but I don't remember the axle being something you could slide that type of wheel over. May be possible to make a barbell type adapter to bolt on the existing hub, but not sure if you could get it strong enough. I would try weights and regular tires first, cheaper and easy to change. I use my 850 with a potato plow with weights, no problem, but I have never tried a turning plow. Another thought is to add a set of tire chains, they do help traction. Mine are cut down car tire chains, usually of snow, but sometimes mud.