Figure 1. The motorcycle drive wheel valve stem is indicated by the arrow. (Photo: C. Roberts)
This case study deals with an accident caused by a sudden motorcycle rear tire deflation. According to a witness, the motorcyclist riding ahead suddenly started to weave as a result of a flat rear tire. The motorcycle eventually traveled off the road and into a ditch, causing severe injury to the rider. The rear wheel of the motorcycle is depicted in Figure 1. The tire had been replaced approximately a month before the accident by a motorcycle shop and was a new tire. The tire bead was intact and appeared properly mounted. However, when pressurized, a severe leak was noted at the valve stem that is indicated by the arrow.
Figure 2. The crack in the valve stem where the air leakage occurred. (Photo: C. Roberts) Figure 2 is a view of the valve stem with the arrow indicating the fractured rubber portion of the valve stem. Figure 3 shows the fracture surface of the valve stem shaft. The arrow points to the striations indicative of crack growth over time.
Figure 3. Fracture surface of the valve stem. (Photo: C. Roberts) Want to continue reading?
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