A strut bar, or commonly known as a strut brace or a strut tower brace, is designed to tie the two opposing strut towers together to form a single unit. This is to minimize the strut tower flex during hard cornering.
When taking a turn, a car's strut towers normally flex. This may cause the losing of some traction. The strut tower brace keeps the strut towers from flexing. They distribute the pressure applied to one strut tower when taking a turn on both towers instead of just one.
This results to improved chassis rigidity. Understeer is reduced, the tire wear is improved and metal fatigue is minimized in the strut tower portion. Adding a brace between these two strut towers is a great way to solidify a vehicle's suspension.