1976 Triumph Spitfire 1.5L Petrol · NPK 548R

The front suspension uses threaded brass trunnions that screw onto the bottom of the vertical links. Triumph specified EP90 hypoid gear oil for lubrication. In practice, owners and fast-fit garages pumped standard chassis grease into the nipples; grease hardens, dries out, and allows road grit to wear the threads. The trunnion seizes solid, causing metal fatigue that snaps the vertical link kingpin under steering load.

On Standard-Triumph four-cylinder engines—most acutely on the long-stroke 1493cc unit fitted to the Spitfire 1500—the semicircular copper-lead crankshaft thrust washers wear excessively. Repeated clutch disengagement pushes the crankshaft forward. Once thrust washers wear down, they drop into the engine oil sump; the unguided crankshaft then machines directly into the cast-iron cylinder block web, destroying the engine casing.

The Spitfire relies on a central double-backbone chassis with fabricated sheet-metal outriggers that support the outer sills and body tub. Road spray thrown from unshielded wheels rots the outriggers, floorpans, rear axle kick-ups and outer sills. Because the sill assemblies provide vital longitudinal stiffness to the open convertible body tub, severe rot causes structural flexing, scuttle shake, and sagging door gaps.