Bodywork

Reducing weight is good way to increase performance, other than a turbo or supercharger. By reducing weight, less energy is being used to accelerate, braking distances are reduced and less energy is used from supporting the weight during cornering, increasing lateral grip. Maximising weight reduction is always advised.

In terms of pure performance, the Increase Body Rigidity upgrade isn't necessary. Newer Vehicles in Gran Turismo 7 already have stiff chassis, further increasing stiffness in low power vehicles may result in understeer. This upgrade should only be considered for high power and or vintage vehicles that have a lot of natural chassis flex, resulting in poor mid-corner traction, more noticeable in older model vehicles Further is discussed in Increase Body Rigidity & Roll Cage.

An in-depth analysis has be given regarding these upgrades in Weight Reduction & Ballast Overview.