• The suspension system rules set forth specific requirements for axles, adjustable axle assemblies, leaf springs, coil springs, torsion bars, and the air suspension system’s regulator valve and exhaust controls.
• The steering wheel and steering column must be securely fastened, the amount of lash (play) in the steering wheel is limited, and the universal joints and ball-and-socket joints must not be worn, faulty, or repaired by welding.
• All components of the power steering system must be operable: no parts loose or broken; belts not frayed, cracked, or slipping; sufficient fluid in the reservoir; and no leaks in the system.

Some additional parts and accessories necessary to the safe operation of a commercial motor vehicle (CMV) include suspension, steering wheel, and power steering systems. The specifications for these systems are described below.

Suspension systems

The rules set forth for suspension systems include:

• All axles must be in proper alignment and no axle positioning part may be cracked, broken, loose, or missing.
• Adjustable axle assemblies must not have locking pins missing or disengaged.
• No leaf spring may be cracked, broken, missing, or shifted out of position.
• No coil spring may be cracked or broken.
• No torsion bar or suspension may be cracked or broken.
• The air suspension system’s air pressure regulator valve must not allow air into the suspension system until at least 55 pounds per square inch (psi) is in the braking system. The vehicle must be level, and air leakage must not be greater than 3 psi in a 5-minute period when the vehicle’s air pressure gauge shows normal operating pressure.
• The air suspension exhaust controls must not have the capability to exhaust air from the suspension system of one axle of a two-axle air suspension trailer unless the controls are either located on the trailer, or the power unit and trailer combination are not capable of traveling at a speed greater than 10 mph while the air is exhausted from the suspension system. This will not prohibit:
  • Devices that could exhaust air from both axle systems simultaneously; or
  • Lift axles on multi-axle units. (393.207)

Steering wheel systems

• The steering wheel must be secured and must not have any spokes cracked through or missing.
• The “play in the steering wheel” (steering wheel lash) must not exceed the parameters set forth in 393.209(b)(1).
  • For steering wheel diameters not listed in 393.209(b)(1), the steering wheel lash must not exceed 14 degrees angular rotation for manual steering systems, and 30 degrees angular rotation for power steering systems.
• The steering column must be securely fastened.
• Universal joints and ball-and-socket joints must not be worn, faulty or repaired by welding.
• The steering gear box must not have loose or missing mounting bolts or cracks in the gear box or mounting brackets.
• The pitman arm on the steering gear output shaft must not be loose.
• Steering wheels must turn freely through the limit of travel in both directions. (393.209)

Power steering systems

All components of the power steering system must be in operating condition, with no parts loose or broken. Belts must not be frayed, cracked, or slipping. The power steering system must have sufficient fluid in the reservoir, and system must not leak. (393.209(e))