What we are discussing here is "tread width," usually defined as the distance between the center of the tread of the left and right tires. The wheel centers are dished and are usually mounted with the dish to the inside, for minimum tread width. You can often dismount the rim/tire from the center, turn the center the other way on the axle, then remount the rim/tire, thus moving the tire outwards by twice the distance of the depth of the dish.
Or you can just move the entire center/rim/tire combination to the other side, ensuring you keep the tread pattern pointing in the correct direction. Front wheels often do not have the dismountable center, so this is the only way to do it.
I just checked the owners manual for my Kubota B7800, and it makes no mention of altering tread width. I have not had it very long and have not looked at the wheels to see what kind of adjustments I might have.
On my 1950 Ferguson TO20, the manual describes in detail how to adjust tread widths for both front and rear. On the rear, the rim can be mounted in four different positions on the center, and the center can be reversed, giving 16 different tread widths from 48 inches to 76 inches in 4 inch steps. On the front, the three-piece front axle allows you to remove two bolts per side and move the outer sections from 48 to 76 inches in 4 inch steps. You can also turn the front wheels around to get out to 80 inches. The manual notes that you should not turn the front wheels around except when absolutely necessary, as it throws additional strain on the front wheel bearings. That may also appy to modern tractors.
GS
RFB was a little quicker and not so wordy. Thanks, RFB!
