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Wheel Versus Track

The majority of armored vehicles need tracks. However there are a number of contingencies where wheeled vehicles perform their task in a more efficient and effective manner such as in counter-insurgency and riverine terrain. These combat vehicles also provide the commanders that additional tactical mobility when reacting to unforeseen situations in mountainous and high altitude areas where lateral movement of armored vehicles is restricted. Hence the wheeled vehicles could also equip the rapid deployment divisions and the paramilitary forces. The choice of a light tank being wheeled or tracked is debatable, however the current light tanks available in the open market are wheeled yet mounting a 120 mm soft recoil gun.

In 1931, the Army purchased a group of tanks designed and built by the fabled J. Walter Christie. He was 66 years old at the time and famous for his pre-World War I front-drive racing cars; front-drive conversions to motorize horse-drawn fire engines; and World War I-era experimental tanks and self-propelled artillery designs. Christie had developed his so-called “convertible tank,” which could run on tracks or on its own road wheels, in 1928, but he called this remarkable innovation the “Model 1940” because he felt it was years ahead of its time. This was not a complete tank because it lacked any armament and had no turret, but it was an astounding machine that could run 45 mph on its tracks and 70 on its road wheels.

The Christies proved only marginally satisfactory. The tank’s complex dual road-wheel drive, steering-track system was troublesome. So was the chain final drive. With its suspension components, each Christie independent road wheel extended almost a foot out from either side of the hull, crowding the interior and making turret-mounting difficult. The track life, like that of most tanks of the period, was poor – only some 500 miles. And the Christies tended to throw tracks in violent maneuvering. The March 1985 Wheeled Versus Tracked Vehicle Study was performed by the HQ TRADOC Studies and Analysis Activity in response to a 15 May 1984 tasking from HQDA ODCSOPS (DAMO-FD). The purpose of the study was to conduct an analysis of the factors used in developing wheeled and tracked vehicle requirements and to lay the foundation for development of specific criteria upon which to base future vehicle requirements decisions. The study team made, extensive use of existing data and examined the "wheels versus tracks issue from the following perspectives: engineering and design, mobility, cost and foreian trends.

Wheeled vehicles are superior for all vehicle mission roles that require either Tactical Support (15% offroad/65% on-road) or Tactical Standard (30% off-road/70% onroad) levels of operational mobility. For vehicles requiring a Tactical High (60% off-road/40% on-road) level of operational mobility, wheeled vehicles are competitive with tracked vehicles in cross-country performance up to around 10 tons gross vehicle weight (GVW). Above this level, wheeled vehicles must rely on higher levels of mechanical complexity and larger overall vehicle sizes in order to provide acceptable levels of cross-country mobility. These efforts tend to become ineffective at about the 20 ton GVW level where the size and mechanical complexity of high-mobility wheeled vehicles render them impractical for military use.

In order to maintain a desired speed, the slip ratio needs to remain stable. This study also showed how a wheeled vehicle?s slip ratio increases as distance traveled increases, compared to the stable slip ratio of the crawler tracked vehicle. Most likely this will cause the wheeled vehicle to eventually get stuck. Tracked locomotion is far superior in sandy soils than wheeled.

Above the 10 ton GVW level, the mobility trade-offs imposed by the wheeled configuration seriously compromises its effectiveness as a direct fire combat platform. The cost advantage associated with the use of wheeled vehicles was found to lie principally in the operating and support (O&S) arena and is on the order of a 25 to 33 percent reduction in O&S costs. The general advantages associated with the use of wheeled vehicles tend to be in the cost and reliability arena and are purchased at the expense of operational utility.

Wheeled vehicles are preferred for all vehicle roles that require either Tactical Support or Tactical Standard levels of operational mobility. For Tactical High levels of operational mobility:

  • Up to 10 tons GVW, wheeled vehicles are preferred. The cross-country performance of high-mobility wheeled vehicles is competitive with tracks and significant O&S cost savings can be realized through the use of wheeled vehicles.
  • In the 10 to 20 ton GVW range, tracked vehicles are preferred for all combat roles. Wheeled and tracked vehicles should be looked upon as competitors for support roles. The decision of whether a wheeled or tracked configuration is preferred for a particular support role is dependent upon what the role is and where it is going to be performed. This decision is best, left to the cost effectiveness analysis process.
  • Above 20 tons GVW, tracked vehicles are required. The size and mechanical complexity of high-mobility wheeled vehicles renders them impractical for military use.

Tracked vehicles are intrinsically superior to wheeled vehicles in the cross-country environment, especially in the softer soils found in the temperate areas of the world. A review of foreign trends revealed that there was not a significant movement among major states to embrace wheeled armored vehicles for tactical use. France was the only major western nation that has made a substantial commitment to wheeled vehicles. Other countries that use wheeled armored vehicles tend to restrict their use to mission roles that complement the tracked force.

The debate over wheeled versus tracked platforms that followed General Shinseki’s October 1999 Association of the United States Army speech for a time diverted attention away from the Army’s effort to transform itself, but the program continued nonetheless. In November 2000 the service chose the eight-wheeled LAV III, soon to be renamed the Stryker, as its new medium-weight armored vehicle.

Since the Army was engaged in Afghanistan and Transformation was emerging as the defining component of Secretary of Defense Donald H. Rumsfeld’s policies, by 2002 the new Stryker 8x8 wheeled vehicles and the brigade fielding them drew considerable attention, both positive and negative, from the defense community, the media, and the general public. A renewed debate occurred, for example, over the effectiveness of tracked versus wheeled combat vehicles. Commentators compared the Stryker’s performance with that of the M113A3. Critics claimed that the wheeled infantry carrier version was too lightly armed when compared to similar vehicles fielded by other armies and that it was less capable than either the M113A3 or the Bradley because it lacked an amphibious capability.

The Army spent considerable time and effort answering negative reports. Wheeled combat vehicles consumed considerably less fuel than their tracked counterparts, reducing logistical demands and the number of fuel convoys needed to support a force. Wheeled vehicles could also travel long distances on their own, while tracked vehicles suffered considerable wear unless carried by Heavy Equipment Transport System (HETS) vehicles. That said, the service nonetheless had to admit that some criticisms of the design were valid and that technicians would be installing necessary modifications as testing and evaluation progressed.

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Page last modified: 27-07-2016 18:53:32 ZULU