Ford 2003 Mustang Workshop Manual page 41

Lateral runout means measuring the movement or "wobble" of a wheel or tire at the sidewall. Radial
runout means measuring the out-of-round at the tread surface.
Rustling
Intermittent sound of varying frequency (100-2000 Hz), sounds similar to shuffling through leaves.
Shake
A low-frequency vibration (5-20 Hz), usually with visible component movement. Usually relates to tires,
wheels, brake drums or brake discs if it is vehicle speed sensitive, or engine if it is engine speed
sensitive. Also referred to as a shimmy or wobble.
Shimmy
An abnormal vibration or wobbling, felt as a side-to-side motion of the steering wheel in the driveshaft
rotation. Also described as waddle.
Shudder
A low-frequency vibration that is felt through the steering wheel or seat during light brake application.
Slap
A resonance from flat surfaces, such as safety belt webbing or door trim panels.
Slip Yoke/Slip Spline
The driveshaft coupling that allows length changes to occur while the suspension articulates and while
the driveshaft rotates.
Squeak
A high-pitched transient sound, similar to rubbing fingers against a clean window.
Squeal
A long-duration, high-pitched noise.
Static Balance
The equal distribution of weight around the wheel. Statically unbalanced wheel and tire assemblies can
cause a bouncing action called wheel tramp. This condition will eventually cause uneven tire wear.
Tap
A light, rhythmic, or intermittent hammering sound, similar to tapping a pencil on a table edge.
Thump
A dull beat caused by two items striking together.
Tick