A rear sway bar is a component of a vehicle's suspension system that creates more stiffness as you drive. The stiffer your suspension is, the less roll you'll feel when you turn your car and the more stable your vehicle will be overall.

Rear sway bars are to help the rear of the vehicle to be stable when driving around turns or maneuvers and when towing another vehicle.

The idea of a sway bar, which is connected to either both front or both rear wheels is that it resists the vehicle's tendency to roll as it corners, thus helping to keep weight on the inside.