Chapter 9 Steering Systems 177
the gears in the steering gear, the size and shape of the
steering arms, and the angles formed by the linkage all
affect the steering action. The percentage of vehicle weight
placed on the front wheels and whether the vehicle has
front- or rear-wheel drive are also factors.
Rack-and-Pinion Steering
Rack-and-pinion steering is a simple system that
directly converts the rotation of the steering wheel to
straight line movement at the wheels. Figure 9-20
illustrates the principle of the rack-and-pinion steering
gear. The steering gear consists of the rack, pinion, and
related housings and support bearings. Turning the steering
wheel causes the pinion to rotate. Since the pinion teeth
are in mesh with the rack teeth, turning the pinion causes
the rack to move to one side. The rack is attached to the
steering knuckles through linkage, so moving the rack
causes the wheels to turn.
Steering Ratio
The size of the pinion gear and the number of teeth on
the gear determine the rack-and-pinion steering ratio. A
large pinion gear with many teeth would turn quickly but
would require a large steering effort. A small gear with a
few teeth would turn easily, but require many revolutions
of the steering wheel to make a turn.
A
Pin
4-way valve
Pinion shaft
Pinion
holder
Power cylinders
Steering rack
Pinion holder
Pinion center
Pinion gear
Pinion holder
center
Steering rack
reaction
Steering
rack
4-way valve
Pin
Gear housing
B
Figure 9-20. A—Rack-and-pinion steering system cutaway showing the pinion shaft and the rack. B—Steering rack reaction in rela-
tion to the direction the pinion shaft and teeth are turned. This particular unit is powered with hydraulic fluid. (Honda)