Abstract: A vehicle C-pillar assembly including a C-pillar, a rear quarter extension, and a rocker panel is provided. The rear quarter extension mounts to the C-pillar and includes an arc portion. The rocker panel mounts to the rear quarter extension to define a horizontal joint therebetween and includes a notch providing space for the arc portion to extend upward along the C-pillar. The rocker panel may include an end and the rocker panel may be secured to the C-pillar so that the end extends rearward of the C-pillar to contact and reduce rotation of a tire mounted adjacent to the C-pillar when a force directs the tire forward. A profile of the rocker panel may be a C shape. The rocker panel may extend from a vehicle A-pillar rearwardly past the C-pillar. The rocker panel may be roll-formed and of an ultra-high strength steel.