Summer 2010 Forward to a Friend

Rack-and-Pinion Steering
Steering Wheel

DECADES AGO, SPORTS CARS ESTABLISHED THIS TYPE OF SYSTEM AS DESIRABLE DUE TO ITS PRECISION AND RESPONSE, AND TODAY MOST PASSENGER VEHICLES HAVE IT AS STANDARD EQUIPMENT.

Glossing over reference to rack-and-pinion steering in specification charts is easy to do. We tend to dismiss it because that’s what all vehicles seem to have. (However, other systems do remain on the market.) Understanding rack-and-pinion steering and its benefits will contribute to appreciating what makes a Subaru, a Subaru.

WHEN YOU TURN THE STEERING WHEEL

With the action of turning the steering wheel to cause a vehicle to change direction, a number of components come into play. Although enhanced by other systems, here are the basics of rack-and-pinion steering:

  • The steering wheel rotates the steering column.
  • The teeth on the pinion gear at the end of the steering column engage with teeth on a rack in the steering gear assembly.
  • The rack assembly moves the tie rod assemblies to which it’s connected.
  • The tie rod assemblies push or pull on the steering knuckles connected to the front wheels, causing the direction in which the wheels are pointed to change from one side to another.

The point of the steering system is to transfer the driver’s rotational force into a lateral one that alters the direction in which the vehicle is traveling. The steering force from the teeth in the rotating pinion gear becomes a lateral force via the gear teeth on the rack.

All Subaru steering systems have power assist. Hydraulic pressure provides added boost at low vehicle speeds to help the driver turn the steering wheel. Pressure is reduced at higher vehicle speeds.

BENEFITS

One of the main differences between rack-and-pinion steering and other types – mostly recirculating-ball steering – is the direct connection of the components. Recirculating-ball systems transfer steering forces through a series of gears and ball bearings that tend to diminish the feel of the tires on the road. That feel is transmitted better by a steering rack. (Recirculating-ball steering systems are better suited to heavy-duty vehicles, because they can be engineered to bring greater forces to bear for turning the front wheels.)

Rack-and-pinion steering also is more precise. A small degree of movement with the steering wheel brings immediate results on the road. Other steering systems tend to have some play in the steering wheel when traveling straight down the road. The rack-and-pinion system has proven more active and fun to drive.

Plus, the simpler rack-and-pinion steering systems are easy to service, which contributes to a lower cost of ownership.

Rack-and-Pinion Illustration

CARING FOR YOUR STEERING SYSTEM

Important things to note about steering system care and maintenance:

  • When checking fluid levels under the hood, don’t overlook the power steering fluid reservoir. (Check it monthly.) Markings on the reservoir indicate maximum and minimum levels for the fluid when hot or cold.
  • Do not hold the steering wheel at the fully locked position (left or right) for more than five seconds, because it may damage seals within the system.