Power steering was once considered an optional luxury, but changes in automobile configurations made this feature essential to most drivers. Steering originally depended only on the driver's muscular exertions, but cars became heavier as equipment was added and tires became softer to cushion the ride. The softer tires hugged the road, but friction also increased so more force was needed especially during turning. The passenger compartment and the engine moved forward as improvements were made to road handling and comfort, but this shifted more of the load to the front wheels. Front-wheel drive also added efficiencies to car operations but complicated the average driver's ability to steer.

At first, steering was adapted to these changes by mechanical improvements to the bearings, linkages to the front wheels, and the gears that transmit the movement of the steering wheel to the front wheels. The "average" driver was changing...