How Hummers Work

Image Gallery: Off-roading The Humvee Base Model. See pictures of off-roading.
Photo courtesy AM General

In 1979, the U.S. Army issued a request for a new vehicle design that could meet demanding standards, including the ability to modify the base vehicle for different missions. Chrysler Defense, Teledyne Continental and AM General submitted design proposals, and after extensive tests and revisions, the Army awarded AM General a $1.2 billion contract to produce their High Mobility Multi-purpose Wheeled Vehicle (HMMWV), better known as the Humvee or Hummer.

The Hummer plays an integral role in the Army's vehicle fleet. The U.S. Marines, Navy and Air Force also use Hummers in various military operations. AM General first offered a civilian version of the Hummer in 1992. In 1999, GM purchased the right to produce vehicles using the Hummer name, so now there are two lines of Hummers in production -- AM General's military vehicles and GM's civilian Hummers.


Hummers have made a huge impact on both military applications and civilian lifestyles. This versatile vehicle seems to embody complex -- and sometimes contradictory -- ideals, from utilitarian workhorse to the ultimate expression of machismo. Even as the military looks to replace HMMWVs as part of its Future Tactical Truck Systems (FTTS) program, the Hummer continues to be a symbol of the U.S. military's presence in combat zones around the world.

In this article, we'll look at the basic military Hummer and its amazing configurations. We'll examine the civilian models -- officially known as Hummers -- currently on the market. We'll also explore the cultural impact of the Hummer.

In the next section, we'll look at the basic military Hummer.


Hummer Specs

Military Humvees
Some military Humvees are used as troop transport vehicles.
Joe Raedle/Getty Images

By the 1970s, Army officials were convinced that they needed to upgrade their fleet of ground vehicles. The Jeep, which was the Army's previous general-purpose vehicle, had outlived its versatility and usefulness in the field. They needed a new, adaptable vehicle that could handle the demands of the evolving nature of combat environments.

The basic Hummer vehicle is 6 feet tall, 7 feet wide, 15 feet long and weighs 5,200 pounds (2,340 kilograms). AM General used a steel frame with five cross members to support the weight of a vehicle with a payload of up to 2,500 pounds (1,125 kilograms), allowing a gross vehicle weight (GVW) -- the weight of the vehicle, passengers and maximum payload -- of 7,700 pounds (3,465 kilograms). In order to keep the vehicle's total weight at a manageable level, AM General used aluminum to construct the body of the car. The aluminum is strong enough to support heavy armaments or carry troops, yet is able to flex when the Hummer travels over rough ground.


A double A-arm independent suspension in the front and rear with hydraulic shock absorbers allow the Hummer to tackle unforgiving terrain. It also has torque-biasing differentials and four-wheel disc brakes, which give the Hummer the ability to continue moving even when some of the wheels lose contact with the ground.

The Hummer is a fully four-wheel drive vehicle -- the engine powers all four wheels at all times. It also has open-differential gears with Torsen differentials. When one wheel begins to slip, it loses torque. The Torsen differential system senses the loss of torque and increases torque to the other wheels. Coupled with the brake traction control system, the Humvee's Torsen differentials give the vehicle incredible off-road capabilities.

AM General outfitted the Hummer with military tires, and some Hummers included a central tire inflation system (CTIS). With this system, a driver can adjust tire pressure without leaving his seat. By lowering the pressure in the tires, the driver could increase the Hummer's grip on rough surfaces, which can be handy if you're trying to drive up a steep hill covered in rocks. Higher pressure is better when driving on even surfaces -- it helps maintain a smooth ride.

Hummers have a 25-gallon (95-liter) fuel tank and can go about 300 miles (480 kilometers) before needing to refuel -- meaning a basic Hummer gets about 12 miles to the gallon, though heavier Hummer variations are somewhat less efficient. As per the Army's request, all military Hummers run on diesel fuel and have an automatic transmission -- the Army wanted all its vehicles to run on the same fuel system and felt that automatic transmissions would be easier for new trainees to learn quickly.

The Hummer has power steering and includes a 12/24-volt electrical system. Either two or four soldiers can sit inside the cab of the vehicle, depending on the variant. According to AM General, the location of the seats on either side of the drive train helps give the Hummer a low center of gravity.

The vehicles have powerful combat locks on each of the doors to help keep soldiers safe. Unfortunately, some soldiers have found it impossible to open the doors if the locks are damaged out in the field. To fix this problem, AM General now includes a D-ring on all Hummer doors. The D-ring is a loop of metal attached to the outside of the Hummer's doors and functions as a place to attach a cable or chain. A winch or similar device can pull the cable, forcing the door open and letting soldiers out of the vehicle.

That's the lowdown on the basic Hummer. Using this as a starting platform, AM General produced 15 different HMMWV variants. They designed 44 interchangeable Hummer parts, allowing the Army to modify, maintain and repair vehicles with incredible efficiency, economy and flexibility.

In the next section, we'll look at some of the variants of the military Hummer.


Hummer Models

Helicopter airlifting a Humvee
Helicopters can airlift Humvees and transport them into the field.
Photo courtesy AM General

The 15 variations on the basic Hummer model allow the Army to use the same vehicle as a troop or cargo transport, weapons carrier, shelter carrier (a vehicle designed to transport electronic equipment) or ambulance. Some variations look almost identical, while others seem to be completely unrelated. All use the same frame, drive train geometry, suspension and lower body.

The current 15 variations fall into two different broad categories -- the A2 model series and the Expanded Capacity Vehicle (ECV) models. Nine models are in the A2 series, including the M1097A2 Cargo/Troop Carrier, the M1097A2 Shelter Carrier, the M997A2 Maxi-Ambulance with Basic Armor and the M1045A2 Armament/TOW Missile Carrier with Supplemental Armor. The TOW missile is a tube-launched, optically tracked, wire-guided missile designed to neutralize enemy tanks and aircraft.


The Army has lots of options when it comes to arming A2 Hummers. Some of the weapons you might find on one include:

  • A .50 caliber M2HB Machine Gun
  • The MK 19 40 mm Grenade Machine Gun
  • A 106mm Recoilless Rife
  • A Giat 30, M781 Cannon
  • TOW and TOW II Anti-Aircraft Missile Systems
  • Milan Anti-Armor Missile System

The Army also wanted some vehicles that could carry heavier payloads without a detrimental effect on the cars' mobility. AM General's response was the ECV series. The M1113 ECV is used in special operations missions and as a communications shelter carrier. The M1114 has upgraded ballistic protection and is used in military police and explosive disposal missions. The M1151 is an armament carrier and the M1152 can either be used as a troop carrier or shelter carrier. The M1165 is used as a command and control vehicle. The M1116 is the U.S. Air Force's variation on the Hummer, with a larger cargo area and turret gunner armor.

Just like a commercial vehicle, there's some optional equipment you can get on a military Hummer. The options available to both the Hummer and civilian vehicles are air conditioning, special paints, a hard top, central tire inflation system and a winch. Here are a few of the options the military can include that are definitely not available on your average set of wheels:

  • " type="disc">
  • Troop seats for up to eight soldiers
  • A deep water (up to 5 feet) fording kit with snorkel
  • An Arctic kit
  • A desert filtration package
  • Pedestal weapons mount
  • Special Ops configuration

In the next section, we'll look at how the Hummer invaded the civilian automobile market.


Civilian Hummers

A civilian Hummer
A civilian Hummer
Daniel T. Yara, morguefile

The American public's awareness of the Hummer really blossomed in 1991 as Operation Desert Storm dominated daily headlines and newscasts. For most Americans, it was the first chance to see the Army's Hummer in action. Many were intrigued by its wide, powerful design, and before long people began to ask AM General if it planned to produce a commercial version of the Hummer. AM General's answer was "yes."

In 1992, AM General began to produce a four-wheel drive vehicle based off the military Hummer. They marketed it as "the world's most serious 4x4." The Hummer shared many of its military cousin’s features, including the brake traction control system that gives the Hummer the ability to adjust torque even when a wheel is completely off the ground. Off-road enthusiasts were overjoyed at the prospect of getting behind the wheel of a car that could tackle courses that would scare a Jeep driver. The car's safety rankings were very high -- but you'd probably expect that from a car originally designed for combat missions.


Civilian Hummers use the same chassis as the military Hummer, and AM General even uses the same manufacturing facilities to build them. From 1992 to 1995, the Hummer used a diesel engine (either a 6.2 or 6.5-liter engine, depending on the year). From 1995 to 1997, AM General experimented by producing a model that used a 5.7-liter gasoline V-8 engine. Unfortunately, the Hummer just weighed too much -- early Hummers weighed in at around 7,000 pounds (3,150 kilograms) -- and AM General went back to using diesel engines after 1997.

In 1999, General Motors purchased the right to produce vehicles under the Hummer brand name. AM General would continue to produce the original Hummer, renamed as the H1, under the GM brand name. GM named later models the H2 and H3. Although GM designed the H2, AM General builds the cars in its facilities. General Motors manufactures the Hummer H3 using its own facilities.


Hummer Options

Evander Holyfield's Hummer
Evander Holyfield's Hummer
Vince Bucci/Getty Images

The Hummer H2 is longer than, but not as wide as the H1, and the H3 is the smallest vehicle under the brand name so far. Even so, you can't describe the H3 as dainty -- it's 85.5 inches (7.1 feet) wide and 186.7 inches (15.6 feet) long. Drivers who love the series find the size empowering, while other drivers often feel intimidated when they encounter such gargantuan vehicles.

The Hummer line is not known for its fuel efficiency. Various models of the Hummer H1 reportedly averaged at around 10 miles per gallon [source:]. Peter Ternes, Hummer's director of global product communications, said that the H2 got 12 miles to the gallon [source: AOL Autos]. The H3 fares the best with 15 mpg city/19 mpg highway. There's also the experimental H2H, a hydrogen-powered Hummer, but because there's no hydrogen fuel infrastructure in the United States, it's not likely to be commercially available soon.


As the Hummer brand has evolved over the last few years, General Motors has introduced more options catering to customer comfort. The earliest commercial Hummer vehicles were only a little more comfortable than their military Hummer counterparts were. The appeal of the vehicle was in its off-road capabilities, not its style or amenities. The biggest concession to customer comfort was air conditioning, something many military Hummers lack.

Current Hummer vehicles have more appealing options like chrome finishing, leather seating, heated windshields, remote keyless entry, power windows and cruise control. You can buy an H3 Hummer with satellite radio and heated seats if you like. Other options cater to rugged outdoorsy types -- winches, off-road hardware, tool kits and trailer hitches are available.

As amenities have increased, the price of Hummers has actually gone down. The original Hummer's price was more than $100,000. The first H2 vehicles were also expensive, though now a 2008 H2 Hummer will cost you about $55,500. The H3 is the most affordable model -- a 2008 H3 is priced between $30,000 and $39,000.

In the next section, we'll look at how Hummers have impacted our culture.


Hummer's Cultural Impact

A soldier works on a Hummer
Spc. L.B.Edgar, U.S. Army

Images and video of Hummers appear nearly every day in reports on the United State's presence in foreign countries like Iraq and Afghanistan. Ever since Desert Storm, the Hummer has been a symbol of the U.S. military. In some cases, critics have pointed out perceived shortcomings in the Hummer's design, mainly focusing on its armor. AM General points out that the Army never demanded extensive armor for its Hummers. AM General does offer basic and supplemental armor for several Hummer models, though these packages only provided limited protection. A direct shot from a relatively powerful rifle could still pierce the armor.

Reports of the Hummer's armor limitations give rise to accusations that the equipment sent to our troops overseas isn't sufficient. Many military outfits up-armor their equipment, installing armor plating directly to the vehicle once they receive it. Adding armor to a Hummer increases its weight, which in turn can affect its performance. In some cases, a Hummer may be better armored but less maneuverable, making it a more likely target for enemy fire. Because of these limitations, critics say the Army should focus on other vehicle options like the Stryker vehicle.


On the civilian Hummer front, there are other issues. Drivers who enjoy challenging their skills and pushing a vehicle to its limits in off-road courses tend to love Hummer vehicles. A Hummer can scale hills that are insurmountable to most other cars. They can go up steep slopes, drive over objects that would obstruct other vehicles and even plow through up to 30 inches of water without a problem.

While Hummers might traverse a difficult obstacle course with relative ease, they face a much more daunting roadblock when it comes to environmentalists and other critics. The Hummers' infamous fuel efficiency -- or lack thereof -- is enough to turn a green-minded person bright red. In California, a state where environmental concerns are prominent in the minds of its citizens, Gov. Schwarzenegger faced criticism for his unabashed love of the vehicles. His involvement during the publicity tour of the H2H hybrid vehicle did little to calm his critics.

Arnold Schwarzenegger and a hydrogen-powered Hummer
California Gov. and Humvee fan Arnold Schwarzenegger fuels up a hydrogen-powered Hummer.
David McNew/Getty Images

Others see the Hummer as a symbol of American excess and gluttony. A few go so far as to place the blame of the country's foreign policy on the owners of Hummers and other SUVs, claiming that we're involved in conflicts in the Middle East due to our enormous rate of oil consumption. Some people just feel the cars are large, ugly, unwieldy and scary to encounter on the road. A few people even take action: Hundreds of people protested at Hummer dealerships on November 15, 2003 -- a day activists called "National Protest Day Against Hummers" in a fit of creative genius [source:].

It seems that growing numbers of Americans are trying to be environmentally conscious. In that environment, the Hummer line of vehicles faces its toughest road yet -- there may come a day when Hummer owners face more than just the scorn of critics. It's ironic that the same vehicle that was a symbol of American heroism, determination and unity in purpose in 1991 has become a divisive symbol both at home and overseas today.

To learn more about Hummers and related topics, cruise over to the links that follow.


Lots More Information

Related Articles
More Great Links

  • AM General
  • "Arnold Wants a Hummer." Indiana Business Magazine. April 1, 1991.
  • GM Hummer
  • "High Mobility Multipurpose Wheeled Vehicle."
  • "HMMWV Hummer Overview."
  • "Hummer FAQ." The Hummer Network.
  • "Hummer History."
  • "Hummer History."
  • Luiz, Gerald. "Military HMMWV." HUMMER @ Off
  • "The History of the Hummer." KASCAR.Real4WD
  • "The Hummer Goes Hybrid.",14632,Soldiertech_Shadow,,00.html
  • Zygmont, Jeff. "The 10 Least Fuel-Efficient Vehicles." December 14, 2005.