What does a strut bar do to a car?
Simple answer: Rigidity
Long answer: Rigidity clearly has an impact on a number of critical areas. Any suspension, for instance, no matter how finely calibrated or advanced in design, will be unable to perform properly if the body flexes and bends under loading. Rigidity also contributes significantly to crash protection, and to the build quality perceived in areas like the small gaps between panels and openings.
Developed using the latest computer modeling and Finite Element Analysis techniques, the rigidity of the Type R has been greatly improved in several areas.
A new, larger aluminum front tower bar replaces the steel bar on the GS-R, and the addition of performance rods to the rear frame end and rear suspension lower arm add additional strength. Key components that have been reinforced include the rear wheel housing, rear pillar upper garter, rear roof rail upper, rear wheel arch extension, rear lower arm bracket, and rear damper gusset.
source: itrsport.com