Why steering joined front wheel is smaller than rear wheel ?
first thing is that front wheel is for direction changer of the tractor. it means it use for the control as well , so more smaller means more easy to control it .more easy to change the direction by steering . if the front wheel as big as rear . than it need more force to apply to take turn to left and right .
suppose you want to take “U” turn by tractor . than it will good if front wheel have little contact with surface area. so small front wheel is wiser idea to take minimum frication .
tractor mainly used for the hauling a trailer or for agriculture or construction work, it mainly used at rough surface of farm , big wheel is good to make its way on rough surface with less torque.
rear big wheel also make the higher center of gravity make safer to drive on rough surface.
there are also used two wheel , three wheel design tractor and four wheel design ,in four wheel there also same size bigger four wheel also used.