IF you work from a shop with a smooth concrete floor, and IF you have to swap, change, or remove a lot of full-size combine, tractor, sprayer or semi truck tires, a wheel dolly is a wonderful investment.
Wheel dollies come in many sizes and designs, but the principle is the same: Imagine a low-slung L-shaped frame on four small dolly wheels. Jack up the tractor, combine or truck from which you need to remove the tire, until the tire is off the floor. Wheel the tire dolly under the tire. A built in hydraulic jack raises the lower portion of the L until the tire is cradled between the tire dolly's two lower arms. Unbolt the wheel from the machine, and use the dolly wheels to back the tire away and roll it wherever it needs to go.
Tire dollies come in many sizes, with many options. Deluxe units have not only hydraulic lift, but are adjustable so the tire can be tilted toward or away from vertical to perfectly align with the wheel hub on the machine. Another feature is to have rollers on the lower lift arms, which allows the tire to be turned while it's on the tire dolly to align the holes in the wheel with the holes in the wheel hub on the machine. (That feature works nice on semi truck tires and big planter or other smooth-treaded tires. Not so well on cleated tractor and combine tires.)
If you're a tightwad, a tire dolly is a luxury. Yes, it is possible to manhandle tractor tires, self-propelled sprayer tires and other 6-foot-tall tires, rolling them across the floor while carefully, CAREFULLY! trying to maintain their balance. Yes, it is possible to use a tractor loader equipped with bale tines and a log chain to lift and move tires and wheels.
But if you want to be safe, and if you want to reduce the chance of a broken foot, strained back or a bale tine getting stabbed through the side window of a tractor cab (it happens...), a wheel dolly is a wonderful option. As combine and tractor tires get taller and incredibly heavier, and the trend toward swapping self-propelled sprayer tires between floater tires/duals to row-crow tires several times a year becomes more common--a wheel dolly starts to make sense.
Figure on spending between $800 and $2500 for a wheel dolly, depending on how big of a one you get, and how many bells and whistles it has. BTW--emergency room visits for a smashed foot, broken leg or other tire-related injury usually start at around $2000.