Tires, Suspension and Powertrain

Let's begin with the elements common to all Stryker configurations. Starting at ground level, the most obvious innovation over earlier light and medium vehicles are the wheels. The Stryker moves on eight wheels, as opposed to the tracks usually found on a tank, heavy truck or armored personnel carrier. A wheeled vehicle is generally much faster than one on tracks, but tracks are capable of traveling on a wider variety of surfaces. So, in keeping with the "best of both worlds" approach of the Stryker project, its tires are built with a new technology that makes them almost as versatile as tracks.

Photo courtesy U.S. Army A fully loaded Stryker Infantry Carrier Vehicle departs the "Dust Bowl" at the Army's National Training Center at Fort Irwin, CA.

CTIS CTIS can be found on other military vehicle systems, including the Humvee, and in commercial heavy trucks. If you simply have to have it for yourself, it's also an option on high-end consumer SUVs like Hummer's H1.

The Eaton/Dana Corporation created a special pressure-control system (CTIS, or Central Tire Inflation System) for the Stryker's eight tires, so that they can be inflated or deflated at will from within the vehicle. This means the Stryker crew can adapt the chassis height and gripping power of the wheels on the fly, giving it much more mobility than a vehicle with fixed tire pressure. A control panel (ECU) in the dashboard is hooked up to sensors and pressurized hoses attached to each tire. This allows the crew to monitor precise tire pressure and make changes with the push of a button. With a top speed of over 60 mph (97 kph), the Stryker is faster than a tank. But thanks to CTIS, like a tank it can travel over both hard and soft surfaces. CTIS also helps to make the Stryker portable. By partially deflating the tires, the Stryker crew can make it more compact for shipment on cargo planes.

The tires are supported by a hydropneumatic, nitrogen-charged, independent suspension system. This works in tandem with the CTIS to create a smooth ride at various heights from the ground.

The Stryker's selectable four-wheel or all-wheel drive is powered by a 350-horsepower, automatic-transmission, Caterpillar turbodiesel engine with a two-speed transfer case. It has six forward speeds and the ability to travel in reverse. Top speed is approximately 65 mph (105 kph), and it can travel 330 miles (531 km) on a 53-gallon tank of diesel fuel. The engine generates 580 lb-ft of torque at 1,400 rpm. It can carry up to 6,500 pounds (2,950 kg) of cargo and generates enough power to tow an additional 10,000 pounds (4,536 kg).

Since this is the same engine found in the Army's medium class vehicles, the Stryker can share repair parts and service personnel with those older units. This is another feature that makes Stryker brigades more efficient and compact.

Stryker Controversy Critics of the Stryker, including military analysts, congresspeople and combat veterans, have argued that the project has not met its objectives and may never fulfill the ambitious ideals of the Army Transformation Plan (see the later section Mission: Vehicle for the New Army for details). Discussion has focused on three main problem areas: Vulnerability - Even with the addition of the slat armor "cage," there is a significant concern that the Stryker is susceptible to RPG attack. As of April 2004, at least one Stryker had fallen victim to an RPG in Iraq. According to reports, of two RPGs fired at this particular Stryker, one got past the slat armor and destroyed the vehicle. (More on slat armor in the next section.) Strykers in the field have also been damaged by bombs and rollover accidents. Weight and Transportability - The 7,000+ pounds of additional armor added to the Stryker before shipping off to Iraq may have increased its weight and height beyond the standard allowable capacity of C-130 payloads. Even without the added armor, during one phase of testing the Stryker's crew had to temporarily remove several components before it could be loaded on a C-130. After landing, it took as long as 17 minutes to ready the Stryker for its mission. General Design Flaws - There have been complaints about several systems not working as well as was claimed by the manufacturer. Some combat troops have reported problems with frequent tire blowouts, and the excess weight from the added armor has caused problems with the self-recovery winch. In addition, there are some reports that the slat armor increases the width of the vehicles to such an extent that they can not travel in groups of two, side-by-side, on narrow roads.