Society of Automotive Engineers: the
professional association of transportation-industry engineers. The SAE
sets most auto-industry standard for the testing, measuring, and designing
of automobiles and their components.
scrub radius: the distance from the point where the steering axis
intersects the ground to the longitudinal line that runs through the
center of the tire's contact patch. Also called "steering
sedan: as used by Car and Driver, the term
"sedan" refers to a fixed-roof car with at least four doors or
any fixed-roof two-door car with at least 33 cubic feet of rear interior
volume, according to measurements based on SAE standard J1100.
semi-elliptic leaf spring: a slightly curved leaf spring that is
attached to a car's body at its ends and to a suspension component near
its middle. One of the two body attachments is a shackle, which allows for
changes in the spring's length as it flexes up and down.
semi-trailing-arm suspension: an independent rear-suspension system
in which each wheel hub is located only by a large, roughly triangular arm
that pivots at two points. Viewed from the top, the line formed by the two
pivots is somewhere between parallel and perpendicular to the car's
series (tire): the numerical representation of a tire's aspect
ratio. A 50-series tire has an aspect ratio of 0.50.
shift gate: the mechanism in a transmission linkage that controls
the motion of the gearshift lever. The shift gate is usually an internal
mechanism; however, in some transmissions: including Ferrari five-speeds
and Mercedes-Benz automatics : the shift gate is an exposed guide around
the shift lever.
shock absorber: a device that converts motion into heat, usually by
forcing oil through small internal passages in a tubular housing. Used
primarily to dampen suspension oscillations, shock absorbers respond to
motion; their effects, therefore, are most obvious in transient maneuvers.
single-rate spring: a spring with a constant spring rate. For
example, if a 100-pound force deflects the spring by one inch, an
additional 100 pounds will deflect it one more inch, and so on until the
spring either bottoms or fails.
skidpad: a large area of smooth, flat pavement used for various
handling tests. Roadholding is measured by defining a large-diameter
circle (Car and Driver uses 300 feet) on the skidpad and measuring the
fastest speed at which the car can negotiate the circle without sliding
slip angle: the angular difference between the direction in which a
tire is rolling and the plane of its wheel. Slip angle is caused by
deflections in the tire's sidewall and tread during cornering. A linear
relationship between slip angles and cornering forces indicates an easily
slushbox: A slang for an automatic transmission.
SOHC: single overhead camshaft: an SOHC engine uses one camshaft in
each cylinder head to operate both the exhaust valves and the intake
space frame: a particular kind of tube frame that consists
exclusively of relatively short, small-diameter tubes. The tubes are
welded together in a configuration that loads them primarily in tension
spoiler: an aerodynamic device that changes the direction of
airflow in order to reduce lift or aerodynamic drag and/or improve engine
squat: the opposite of dive, squat is the dipping of a car's rear
end that occurs during hard acceleration. Squat is caused by a load
transfer from the front to the rear suspension.
steering axis: the line that intersects the upper and lower
steering pivots on a steered wheel. On a car with a strut suspension, the
steering axis is defined by the line through the strut mount on top and
the ball joint on the bottom.
steering feel: the general relationship between forces at the
steering wheel and handling. Ideally, the steering effort should increase
smoothly as the wheel is rotated away from center. In addition, the
steering effort should build as the cornering forces at the steered wheels
increase. Finally, the friction built into the steering mechanism should
be small in comparison with the handling-related steering forces.
steering gain: the relationship between yaw and the steering
wheel's position and effort. All three should be proportional and should
build up smoothly.
steering geometry: the group of design variables outside the
steering mechanism that affect steering behavior, including camber,
caster, linkage arrangement, ride steer, scrub radius, toe-in, and trail.
steering response: a subjective term that combines steering feel
and steering gain.
straight-line tracking: the ability of a car to resist road
irregularities and run in a straight line without steering corrections.
stroke: The distance between the extremes of a piston's travel in a
strut: a suspension element in which a reinforced shock absorber is
used as one of the wheel's locating members, typically by solidly bolting
the wheel hub to the bottom end of the strut.
sump: the space in the engine block under the crankshaft into which
the oil drains from its various applications.
supercharger: an air compressor used to force more air into an
engine than it can inhale on its own. The term is frequently applied only
to mechanically driven compressors, but it actually encompasses all
varieties of compressors-including turbochargers.