The Isuzu Impulse RS rear hub and spindle assemblies wouldn't last more than around 30,000 miles and since production was cut a long time ago, a high demand from enthusiasts was needed. The factory design had ball bearings (also known as angular contact bearings) that ride in the hubs machined grooves. Once the assembly failed, the hub's interior was damaged, requiring a whole new assembly. This problem persisted ever since the car came out and it was never fixed.
The Overspeed solution utilized a much more modern dual row tapered roller bearing that was pressed into the hub, which benefits from:
Replacement of bearing if failure occurs, instead of scrapping the entire assembly
Extend life due to withstanding more load in the axial direction during spirited driving sessions especially.
Better control of the pre-load in the axial direction once assembly is torqued down.
