Wheel spacers are devices that create space between an automobile's wheel and the hub, thus increasing clearance from the inner wheel well. This is done to give a vehicle a wider base with better stability. Also, they give the ability to put larger tires on an automobile.
In the United States, wheel spacers are not currently regulated under the Department of Transportation's current legislation. There are no existing federal laws that prohibit wheel spacers for on-road use.
Although the U.S. Federal government does not regulate wheel spacers, local and state governments do have the right to prohibit their use. These laws frequently change. To be sure of what the laws are in a particular area of the country, contact a city or state's law enforcement agency or automobile regulative body and inquire from them.
To avoid any potential issues involving legality, some manufactures of wheel spacers market their spacers as being intended solely for off-road use.