Running Gear Handbook

This catalog is to assist the running gear designer in the selection and proper use of AEROL components. Three different types of Running Gear and Accessories are described in this catalog as follows:

Banjo Mounts

Wheels and spring suspension mounted on the side of the carriage. Spring suspension has rotary movement.

SAM Suspension Unit

Wheels and spring suspension mounted on the side of the carriage. Spring suspension has linear movement.


 Includes limi-torq and surge type brake actuator towbar.

Military Running Gear

In addition to Commercial Running Gear, AEROL manufactures an extensive line of mobile equipment components and assemblies that meet the requirements of Military Specifications.


AEROL provides running gear with Ackerman steering, fifth wheel steering and synchronous steering options plus various types of tow bars.

Safety First

Aerol products are designed with a margin of safety that years of analysis and experience has shown to be more than capable for their rated capacities, in the service specified. However, operation at higher-than-rated speeds or on a terrain or in a service other than specified, overloading, using mismatched components or, neglecting to maintain correct tire inflation or the recommended lubrication frequency, can cause sudden failures.

We recommend maximum speed and payload, correct tire inflation pressure, torque for wheel bolt (lug nut) and bearing maintenance information be displayed, along with other safety information, in a conspicuous place on the vehicle. Equal side-to-side loading is recommended.

Designers not familiar with factors influencing the stability of towed vehicles (especially at high speed) should contact Aerol Engineering early in the design stage since this stability is dependent on chassis dimensions and weight distribution. Anticipated extremes of terrain and/or operating conditions should be brought to the attention of Aerol’s Engineering Department.

How To Determine Capacity

Capacity, in all cases, refers to the load measured at the ground.


In assembling running gear components, it is desirable to match the capacities of the rig, tires, wheels, brakes, etc. as closely as possible. The component with the lowest capacity determines the capacity of the entire running gear. For example, if an axle beam rated at 5,800 lbs. Is matched with wheels rated at 2,600 lbs each (5,200 lbs/axle); tires at 5,100 lbs. and brakes at 5,000 lbs, then the axle assembly is rated for 5,000 lbs. If you select larger capacity brakes, say 5,200 lbs, the axle capacity is then rated by the next lower capacity component in the assembly. Therefore the axle assembly should be rated at 5,100 lbs.


All load carrying components and brakes in this catalog have rated capacities at given speeds. Except where so noted, capacity of components is given at 20 mph. For low speed service ON PAVED SURFACES, WHEEL, HUB AND AXLE capacities may be increased. Also, highway speed running gear is available. CONSULT AEROL ENGINEERING DEPARTMENT.

Tires may not exceed the ratings shown in the tire capacity charts. Individual tire manufacturers’ ratings may vary slightly from the values shown and should be used when known. Tire inflation pressure must not exceed the inflation pressure shown for the wheel on which it is to be mounted.

Brake ratings are not to be exceeded, regardless of speed, without approval of Aerol’s Engineering Department.

Spring capacities remain constant regardless of speed.

Wheel Bolt (Lug Nut) Torque

Lug nuts should be re-torqued to the following values after the first 100 miles of operation and should be checked periodically.

Thread Size Torque (ft-lbs) Torque (kg-m)
1/2″-20     (12.7 mm) 70-90 (9.6-12.4)
5/8″-18     (15.9 mm) 125-140 (17.2-19.4)
3/4″-16     (19.0 mm) 450-500 (62.2-69.2)

Running Gear – Banjo Continued:

The Aerol Banjo Mount running gear concept comprises a wheel, mounted on stub axle fitted to a shock absorption unit, that can be bolted to the side of an item of ground service equipment. The necessity for an axle beam is thus eliminated, and the load cradled between the individual wheel units permits

lower center of gravity.

Due to the radial arm mounting of the axle in the Banjo Mount, when the

wheel strikes an obstruction, the resultant motion is upward and backward, or

in the direction of the force applied to the wheel. Therefore, the minimum shock is transmitted to the pay load. Because of this design, the Aerol Banjo Mount is especially suited to the carrying of delicate loads.

The Aerol Banjo Mount is designed for loads up to 1,000 pounds (454 kg)per wheel and can be used with AEROL Cushion Tread Wheels in sizes 13 inch, 16 inch, and 21 inch diameter, or with industrial pneumatic wheels in the corresponding sizes, 3.50-6, 4.00-8,and 6.00-9, described in United States Military (USM) specification MIL-W-8005.

Steerable front-end units and rigid rear-end units may be fitted with parking

brakes with ratchet pedals, or with levers for cable or rod actuation. Service brake systems are also available. The Banjo Mount is equipped with a “Normally On” Brake System.

The Ackerman steering principle is used, with tie-rods controlling the steerable front wheels from the tongue and tow-bar assembly. The tow-bar assembly may include a vertical stowage latch, over-steering linkage, a surge system to automatically actuate hydraulic service brakes, a mechanical dead- man linkage to actuate the parking brakes, safety chains, and a quick release pin for easy removal of the tow bar.

All components of the system re-designed to exceed the requirements of USM specification MIL-M-8090 for type II mobility.

Running Gear – SAM Continued:

The Aerol SAM Suspension Unit is a heavy duty running gear concept comprising a shock absorbing unit that can be bolted to the side of ground support equipment, and a stub axle on which any one of a wide selection of wheels can be mounted. The basic unit is used in front and rear installations, and can be made rigid or steerable by the addition of a lock pin or a steering arm. This flexible design permits front and rear steering for maneuvering in restricted areas, or conventional front end steering when the equipment is towed.

Like its smaller cousin, the Banjo Mount, the SAM Suspension Unit can be supplied to handle a wide range of loads up 5,000 pounds (2268 kg) per wheel. The load rating can be easily changed in the field by the addition or removal of standard springs. No special tools are required., nor is it necessary to dismount the unit.

Parking brakes may be added, with ratchet pedals, or with levers for cable or rod actuation. Hydraulic service brake systems are also available, with a mechanical parking brake feature if required. Hydraulic brakes may be operated from the hydraulic system of the towing vehicle, or by means of a surge system incorporated in the tow-bar assembly.

The Ackerman automotive steering principle is used wherein the wheels are controlled by tie- rods connected to the tow-bar and tongue assembly. The tow-bar assembly may include, In addition to the surge system previously described, and stowage latch, over-steering linkage, and safety chains.

The stub axle will accommodate 16 inch or 21 inch AEROL Cushion Tread Wheels, conforming to USM specification Mil-W-21985, industrial pneumatic wheels in sizes 6.00-9, 7.50-10, and 9.00-10, as described in USM specification MIL-W-8005, transport type and other commercial pneumatic wheels.

The SAM Suspension Unit was originated by AEROL CO., in response to a request by the armed forces for reliable and versatile individually sprung wheel and mount assembly. All components of the system are designed to exceed the requirements of USM MIL-M-8090, for Type Il mobility. Interchangeability of components parts, and the wide adaptability to all types of ground support equipment with varying payloads, has been a significant contributing factor in standardization with resultant reductions of spares inventories and improvement in logistic support.

AEROL CO., has developed a device to accommodate sharp turns; the Mark II Limi-torq. When the tow-bar is turned to the point where the inboard wheel has reached its maximum cramp angle, the steering mechanism is disengaged, and the tow-bar is free to swing further without applying additional force to the steering linkage. If the tow- bar is then moved in the opposite direction, it swings freely to the position corresponding to the maximum cramp angle at which point the steering linkage is engaged, and during further movement of the tow-bar the wheels are controlled. When the steering linkage is disengaged from the tow-bar, the wheels are positively locked in the cramp angle position.

Service brakes, as required by USM Specification MIL-M-8090 on towed equipment, must operate in response to the driver of the tractor. Hydraulic brakes connected to the brake system of the towing vehicle, electric brakes, and air-over-hydraulic brake all have disadvantages; mainly the required compatibility between all towed and towing vehicles. The problem of providing service brakes is best resolved by using the AEROL surge type brake actuator. This device responds to any decelerating force of the tractor pintle hook on the lunette eye of the trailer tow-bar, to actuate the hydraulic brakes of the towed vehicle.