Panels and Frames
Panels and Frames tests panel types, frame layouts, mountings, alignment checks and the difference between cosmetic fit and structural alignment. Expect questions on ladder and perimeter frames, subframes, body mounts, datum points, control points, diagonals and panel gaps.
Core rules
- Panels may be outer cosmetic, inner reinforcement or structural. A frame may be ladder-type, perimeter, space-frame or integral with the body.
- Alignment is checked against datum and control points, not against damaged panels.
- Use diagonal comparisons and centre-line checks to detect sway, diamond or mash damage.
- Body mounts and subframe bushes affect panel gaps and steering geometry; check them before condemning a frame.
- Panel gaps should be even and within specification; adjust hinges, catches and mounts before forcing panels.
- Isolate the frame from the body when pulling, and use rated chains and clamps.
Worked example
A vehicle has a wide gap at the front door and a tight gap at the rear. Measuring the underbody control points shows the left front rail is 12 mm rearward. The correct conclusion is structural mash rather than a door-hinge fault. The repair plan is to anchor the vehicle, pull the rail on a straightening bench, re-measure datum points and then adjust the door. Reasoning: panel gaps are symptoms; control-point measurements locate the cause.
Traps
Do not measure to a crumpled outer panel. Do not pull until the vehicle is anchored. Do not confuse wheel alignment with body alignment. Do not assume new hinges will fix a twisted shell.