The heavy, lengthwise structural members running from the front to the rear of a traditional vehicle chassis. Crossmembers span between the two frame rails to create a rigid ladder frame. The engine, transmission, suspension, and body tub are all mounted directly to these rails, making them critical for structural integrity and crash safety.
The passenger side frame rail is rusted through right behind the rear axle, so this truck won't pass inspection.
Do not mix it up with
- Unibody: A unibody integrates the frame and body into a single structure, whereas a frame rail is a distinct, separate chassis beam.
Related terms
Unibody
A unibody is a vehicle construction method where the floor pan and body shell are welded into a single load-bearing structure.
Platform
The shared underlying architecture and mechanical components used across multiple vehicle models.
Suspension
The system of springs, dampers, and linkages connecting a vehicle to its wheels.