The Mark trains use a slightly different bogie scheme than the Seattle ALWEG and Hitachi ALWEG monorails. Where the Seattle and Hitachi trains have independent bogies that have load wheels that extend into the cars, the Mark III/V, Mark IV and Mark VI trains have load wheels at the ends of the cars, which are attached to the substructure. Also, instead of two tires per axle on the Seattle and Hitachi trains, there is only one on the Mark III/V, IV and VI trains. These load tires are 445/65R22.5 Michelin XTE2 46.6" diameter , 17.8" wide truck tires, the same ones you can see on a dump truck or cement mixer. The tires are nitrogen-filled to reduce the possibility of fire. They also have run-flat capability. These tires will last 100,000 miles in normal operation. Maximum rated speed for these tires is 65 mph (105 km/h). The load capacity of these tires are 12,800 pounds (5806 kg) each at maximum inflation. There are 12 load tires per 6 car train and 48 guide tires per 6 car train. These guide tires are 21.5" in diameter. In addition, there are two steering wheel tires under each cab car to help steer the suspension up to 3 degrees in either direction. Steering is accomplished in the intermediate cars by the relative geometry of the two adjacent cars. Thus, all 12 load tires are steerable, and the tires are always tangent to the curve. The main suspension of the cars above the axles is done with air bags (also called air springs). The air bags are automatically inflated/deflated by a leveling valve, which allows varying load conditions. There are also vertical hydraulic shock absorbers. For further information on the suspension system, see the Bombardier Mark VI patent.
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