MMC initiated a voluntary safety inspection campaign in January this year to check the wheel hubs of certain heavy-duty trucks and buses. The campaign was extended in July to cover both wheel hubs and alloy wheels. As of November 9, 2002, MMC had inspected 94.2 percent of vehicles covered by the initial campaign and 61 percent of vehicles subject to the extended campaign.

Since MMC's previous announcement on July 26, one incident of a tire coming off was reported on August 7. This was a rare case, however, as the vehicle in question was affected by a previous accident.

Despite conducting stringent inspections, MMC has learned of four other cases since October 7 in which a tire has come off due to hub or wheel wear and tear that exceeded the stipulated levels for replacement. Faulty measuring equipment and misidentification of wheel type caused them to be overlooked. Although the current problem stems from glitches in organizing inspections, MMC strongly acknowledges the need to address the problem as quickly and thoroughly as possible.

MMC has taken a number of steps-including using information gained from accidents caused by overloading and use under severe conditions-to detect faults during inspection. But it is impossible to detect all problems that may arise during overloaded use and maintenance related problems such as over-tightening of bolts.

To address such problems and assure the highest levels of traffic safety, MMC has decided to replace all hubs that were not replaced during inspection, regardless of current wear and tear.

Reference

1. Additional hub replacement

2. Progress of initial inspections (from January 22)

*Replacement level: Wear on hub of 0.8mm

3. Progress of extended inspections (from July 26)

*Replacement level: Gap between hub and wheel of 0.9mm, or wear of 0.7mm on wheel.