Driving a truck, especially when pulling a trailer, can present plenty of challenges. Whether it's out on the highway, competing for space with darting cars and SUVs, or easing the precious cargo into tight spaces, there are times when the driver wishes for an easier way. The development of the Quadrasteer unit has opened the door for this hope to become reality.
There have been four-wheel steering units developed for passenger cars, but the technology has now opened the doors for application on larger vehicles. Delphi Automotive developed their "steer by wire" system to an action/reaction theory. The Quadrasteer unit's rear wheels (reaction) will turn in coordination with the front wheels, creating greater maneuverability and ride stability.
The role of the rear wheels is dependent on the speed of travel of the vehicle. At lower speeds, the rear wheels will turn up to 12 degrees in the opposite direction of the front wheels. This is called the "negative" phase. There is a range of speed where the rear wheels remain neutral. Steering at higher speeds (the "positive" phase) will see the rear wheels turning in the same direction as the front wheels and at a similar angle.
The change in steering at lower speed is best felt when pulling a trailer or maneuvering with a load. The trailer will tend to follow the vehicle path closely, rather than the jackknifing opposing of a conventional truck/trailer combination. The rear wheels serve to stabilize the angle.
Towing to the track is also greatly enhanced by the Quadrasteer system. Positive rear steering (wheels turning in the same direction as the front wheels) increases the stability of the tandem, protecting it from hazards like wind gusts, road-surface obstacles, and disturbances created by large vehicles passing by. Trailer sway is generally reduced at highway speeds because of the reduction of vehicle yaw designed into the system.
The driver retains the option of changing the steering from conventional two-wheel to four-wheel with the simple push of a button. There is no need to remove yourself from the driver's seat to accomplish this. There is also a setting for enacting the four-wheel steering with a trailer. In addition, the system has a default setting that is automatically enacted if there would be damage to the Quadrasteer control unit. Should there be damage, the system would return to conventional, two-wheel steering.
The system works through a series of sensors. A handwheel position sensor works in harmony with vehicle speed sensors to report data to a control unit. The control unit determines the positioning of the rear wheels, choosing which phase is applicable. The steering position sensor is located on the steering shaft, monitoring the rotation of the shaft. The speed sensor is located at the rear wheels, with the actuator assembly behind the rear axle assembly. The control unit is mounted near the left rear wheels and receives the input for the sensors and dash-mounted mode selector. The control unit works in conjunction with the overall vehicle communications network.
Turning radius for maneuvering (such as parallel parking without the trailer) is unequalled. The turning circle is reduced by as much as 20 percent. Turning radius comparisons have found a vehicle like a Chevrolet Silverado equipped with Quadrasteer to have a similar turning capability of a much smaller car, such as a Honda Civic.
The Quadrasteer unit is an option on selected GM vehicles, including the Chevy Silverado and the GMC Denali. It carries a price tag in the neighborhood of $5,000 on the sticker, but its popularity and obvious advantages counter that additional cost. Road tests, including towing tests, have found obvious benefits in its use.