Wheel adaptors are metal spacers that are installed between a vehicle's hub and the wheel. Because the spacer is located between the wheel and the hub, it places the wheel further away from the body and suspension.
Wheel spacers locate the wheel further away from the suspension, which serves to widen the track. This in turn improves grip and stability.
The closer a wheel is to the outer edge of the bumper and bodywork, the better the car may look. A more aggressive appearance and better "stance" (how the car sits on the road) is often one of the primary reasons for installing wheel spacers. Spacers are often utilised on cars that have wider, custom bodywork.
Added Stress to Suspension Components
One problem with wheel spacers is that because they are further away from the suspension and hub, they increase the forces that are applied to these parts. Automotive engineers carefully design all of the components of a car to work together, and wheel spacers change the specifications. Wheel spacers can cause items like wheel bearings to fatigue and fail sooner than they would otherwise.
Interference With the Fenders
If the car that the spacers are fitted to does not have modified bodywork to accommodate the wider track, the tires may interfere with the bodywork, as they are now further from the suspension.
May Require New Hardware
Wheel spacers may require the use of longer lug nuts or lug studs to safely hold the wheel in place.