Some vehicles cannot be towed with four wheels on the ground. For these vehicles, a tow dolly may permit them to be towed with the drive wheels off the ground. The restriction against towing wheels-down may occur with both rear wheel and rear wheel–drive vehicles. If in doubt, check with your manufacturer for information — do not risk voiding the warranty with improper towing.
The costs for tow dollies and towing wheels-down are usually comparable due to the additional modifications that need to be made for either towing option.
In the RV world, you will find those who feel their way of towing a dinghy is the best way and can't be persuaded to change their minds. Look at both options — wheels-down and dollies — and make your own decisions as to which meets your present and future needs.
Tow dollies do have some disadvantages compared to tow bars. Tow dollies will require more space for storage; this can be a concern if you have limited space at home in a garage or yard, or while you are on the road. Some RV campgrounds may have sites that are long enough for the tow dolly to stay hooked up while you are camping, but you should always check when you are making reservations to see if you will need to unhook, and, if you do, if there is space available to store the dolly while you are there. If the dolly has to be removed, that is one more thing you will need to hook up when it is time to move on. Tow bars generally just fold up after the toad is removed for easy storage.
Tow dollies are basically ramps attached to a towing hitch that is attached to the RV using a standard hitch configuration. The toad has to be driven onto the ramps and then secured using chains or heavy-duty webbing tie-downs. Many people find getting the vehicle properly situated on the tow dolly ramps very challenging. If this is not done properly, the car could roll off or could drive over the ramps, causing damage to the undercarriage. The tie-down apparatus can also cause damage to the vehicle if not attached properly. More challenging is loading rear wheel–drive vehicles that must be backed onto the tow dolly.