Why is torsional stiffness important in vehicle body design?

Torsional stiffness (Nm/degree) determines how much the body twists when subjected to asymmetric loads (like one wheel hitting a bump). Higher stiffness ensures predictable handling by maintaining suspension geometry, prevents door/window seal issues and squeaks/rattles, and provides better NVH characteristics. Modern unibodies target 25,000-40,000 Nm/deg. Convertibles require additional reinforcement due to absence of roof structure. Stiffness is measured using K&C rigs or calculated via FEA.