Dana Spicer has developed a new air-ride steer-axle suspension system that significantly enhances handling and control characteristics while
improving ride quality. The company’s new FrontRunner suspension combines traditional steel taper-leaf springs with air springs and a patented roll-control device to overcome the age-old compromise between ride quality and roll stiffness.

The taper-leaf springs, said to be 2.5 times stiffer than existing products, provide lateral stability while the air-spring piston (pedestal) and the bag itself are optimized for variable spring rate. The key to the smooth ride lies in the unique hollow pedestal design, which provides a higher volume of air inside the spring. In addition, the base of the pedestal is tapered inward, creating a greater volume inside the airbag as it wraps itself around the pedestal while compressed. The larger volume of air improves ride. The pedestal is mounted on a base that’s wider than the air bag, limiting the downward travel of the lower end of the air spring, forcing it to expand outward, and dampening the downward travel. The result is large-air-spring performance from a relatively small spring.

Roll stiffness is accomplished through a unique roll-control tube fitted into the rear section of the suspension. As the weight is transferred from the
right to the left side, the tube twists, absorbing and limiting the forces causing the vehicle to sway. The tube is triple-welded into the triangular brake-reaction links fitted to the suspension. Dana says the roll control tube can be tuned or “dialed in” to the exact OEM’s ride-profile
requirements.

The FrontRunner suspension was conceived to accommodate the higher front-axle brake torque that will result from the Federal Motor Carrier
Safety Administration’s anticipated stopping-distance regulations, expected to be in place in 2007.

Mark Davis, Dana Spicer’s product manager for steer axles, says reduced stopping-distance regulations will put more pressure on brakes and
on front suspensions. “They will need to be larger and stronger to handle brake torque,” he says. “While some fleets might settle for a poorer ride in order to meet the new stopping distance, FrontRunner will meet the requirements and maintain the ride.”

The FrontRunner design accounts for larger brake torque through features such as the variable-rate air-spring assembly and brake-reaction links.

These are a pair of triangular frames fitted to the rear portion of the taper-leaf spring which limits spring wind-up during a brake application reducing brake dive dramatically.

Weight reduction up to 75 lb is possible with the FrontRunner suspension versus existing systems, Dana says. Additional weight saving is
expected over suspensions designed for the higher loads from anticipated stopping distance regulations.

Some OEs are talking about 13,200- or 14,000-lb front axles to handle the higher brake torque coming with the new stopping distance rules,
says Davis. “We see these regulations eventually dictating the use of larger torque steer-axle brakes. The design of the FrontRunner suspension has taken this into account and already accommodates these brakes.”

FrontRunner suspensions will be compatible with most current steer axles and wheel-end equipment, allowing for continuity of existing assembly, maintenance, and service procedures. It’s scheduled for limited release in April 2006, and is expected to achieve full production status during the
fourth quarter of next year.

A recent 60-mile test-drive along Michigan’s I-94 demonstrated the FrontRunner’s effectiveness for Contributing Editor Jim Park.

“It holds the road as well as any taper-leaf suspension, and even steers straight through pavement ruts,” Park reports. “Most notable was the lack of shock felt through the steering wheel when the front axle struck a bump. I could certainly feel the tandems hitting the same bump, but only felt a mild thump through the steering wheel. When cornering, the tractor wasn’t so inclined to lean away from the turn, and in a hard brake application, I experienced barely any brake dive – about half the dive compared to the truck with the standard suspension.”