Technical Analysis

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Technical Analysis: Hub Defect of Mitsubishi Motors Trucks and Buses

[Surce] The original Fuso wheel hub was designed in 1983 and many point to type "D", built between 1992 and 1996, as the one being at the center of controversy. Some fault all except types A and F. It appears that raw forging and machining, both had changed for D but Mitsubishi Motors Truck division (now Mitsubishi Fuso and Bus) tested it only under laboratory conditions skipping the usual dynamic and on-vehicle testing.

One analysis that seems to explain many of the wheel hub failures, points to stress fractures at the meeting place of hub and flange containing the studs, brakes and wheel. Tight machine radius or too-thin cross section can cause this. There could be other causes like the tool path, production machine problems, setup or even suspension design. Another analysis points to forging problem of not being able to form a raw shape without problems like voids or cross-section irregularities.

Mitsubishi Fuso attributed hub defects to insufficient melting and said that failure is more likely for trucks and buses turning under load, more than in vehicles turning sharply.

A few links in reverse chronological order.

Arrest of Fuso executives
Criticism of MMC by Governement, victims, lawyers
Fuso Trucks in Danger of Losing ISO 9001 Certification
First reaction to MMMC's Fuso Hub Defect Cover-up Scandal
Fuso Truck Hub and Wheel Defect Cover-up Background