MIL-B-45367AA
be continuous from bumper to bumper or shall be continuous and of the same cross-section at
least from the rear bumper to the forward front suspension hanger bracket. When continuous
frame rails are furnished, the section modulus and the resisting bending moment of the frame
rails shall be as recommended by the chassis and body builder(s) to support the body and
specified load under severe operating conditions. When a noncontinuous frame rail is provided,
the front rail section shall be reversed to provide clearance for mounting a diesel engine between
the frame rails; the front and rear rail sections shall be overlapped and joined together by both
bolted and welded construction; and the resisting bending moment shall be not less than
640,000 inch-pounds for the main rail section and not less than 390,000 inch-pounds for the front
rail section. The bus chassis shall be built by the bus body builder or to the bus body builder's
specifications for the specific model being furnished. The chassis frame or unit body and frame
and undercarriage shall be so designed and constructed as to support body and load and to
maintain stability under severe operating conditions.
3.4.8 Suspension. The vehicle shall be equipped with the bus manufacturer's standard or
optional system with components having a rated capacity at least equal to the load imposed on
each member, measured at the ground, with the vehicle loaded to its specified GVW. The
vehicle shall be provided with a spring, full air, or combination spring and air suspension on the
front axle. Rear suspension shall be full air. The vehicle shall be provided with hydraulic
double acting shock absorbers, not less than two on the front and two on the rear suspension.
Suspension shall be provided with a mechanism at each wheel to assure lifting of the wheel and
axle when jacking the vehicle from the applicable jacking location. Air systems shall
incorporate leveling valve(s) with a time delay to avoid constant air consumption. Shock
absorbers and airbags shall be fabricated of materials capable of operating in ambient
temperatures from minus 50°F to plus 125°F. The suspension system shall be recommended and
warranted by the chassis supplier to meet specified conditions under mobile operating
conditions.
3.4.8.1 Front suspension. The spring, full air, or combination spring and air suspension
design shall be such that the natural frequency of vertical vibration at the front wheels under all
conditions of loading shall not exceed 2.0 cycles per second. Torque rods shall be provided if
available as manufacturer's standard or option to increase longitudinal and lateral stability.
3.4.8.2 Full air rear suspension. The rear axle equipped with full air suspension shall
have two or four air springs of adequate diameter. The suspension design shall be such that the
natural frequency of vertical vibration about any transverse axis shall not exceed 1.5 cycles per
second at rated capacity for the specified GVW. The full air system shall have none of the
spring weight carried on anything other than air springs. No other spring medium such as leaf,
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