Wheel Balancing Definitions

Back-Coning - When the wheel requires the cone to center the wheel on the balancers shaft from the backside, primarily due to the chamfer of the wheel. Also referred to as Back-Cone Mounting.

Backspacing - The distance measured from the mounting face to the back edge of the wheel.

BDC -The abbreviation for bottom dead center, also referred to as 6 o'clock.

Bead seating - The process of seating the tire to the rim. Bead seating preferably occurs just after the tire and rim have been assembled, but may not happen until the car is driven after balancing has been performed. With the application of the GSP9700 Vibration Control Center load roller, bead seating can be accomplished before balancing. However, the load force and its' relatively short duration will not necessarily solve defective mounting of the tire bead seat to the rim seat.

Bolt Pattern Circle - The diameter of an imaginary circle drawn through the center of each lughole.

Computerized Vibration Analyzer -A device used to determine the frequency of the vibration by isolating the vibrations with the greatest magnitude.

Cycle - One complete disturbance.

Dampen - To decrease the magnitude of a vibration or sound.

Dampers - Used to reduce the magnitude of a given vibration. Rubber is commonly used to isolate and dampen vibrations.

Dataset® - The inner and outer electronic arms on the GSP9700 Vibration Control System. By positioning the Dataset arms and entering data using the foot pedal, rim dimensions can be recorded for balancing.

Dynamic Balance - A procedure that balances the wheel assembly by applying correction weights in two planes so that up & down imbalance and wobble imbalance are eliminated.

Electro-Mechanical Ear - A device used much like a doctor's stethoscope and is for noise diagnosis problems only.

ForceMatching® - A method of aligning the high spot of the tire's radial Road Force Variation with the low spot of rim runout to decrease rolling vibration in the wheel assembly under load.

Forced Vibration - Vibrates when energy is applied.

Free Vibration - Continues to vibrate after the outside energy stops.

Frequency - The number of disturbances that occur per unit of time.

Front-Coning - When the wheel requires the cone to center the wheel on the balancers shaft from the front. Also referred to as Front-Cone Mounting.

Harmonic - A vibration that is identified by the number of occurrences per revolution. For example, a 1st harmonic vibration has a once per revolution vibration component.

Hertz - A unit of frequency: one disturbance per second.

Hub centric -The wheel is centered using the center hole of the wheel.

Lateral Runout - The amount of side-to-side movement as the tire/rim assembly rotates.

Lug centric - The wheel is centered using the lugholes rather than the wheel center hole.

Magnitude (Amplitude) - The amount of force or the intensity of the vibration.

MatchMaker® - GSP9700 software feature which allows the operator to match up four identical tires on identical rims, to achieve the optimal combination of match mounting.

Natural Frequency - The point at which an object will vibrate the easiest.

Order - The number of disturbances per cycle (rotation). For example, a 1st order vibration occurs once per cycle, and a 2nd order vibration occurs twice per cycle.

Phase - The position of a vibration cycle relative to another vibration cycle in the same time reference.

Phasing - The cycle pattern of two or more vibrations that overlap and combine to increase the overall magnitude.

Pressure Ring - The accessory used to prevent the wing nut from contacting the wheel when on the balancer shaft.

Radial Force Variation (RFV) - A term describing a measurement of the tire uniformity, under load, measuring the variation of the load acting towards the tire center.

Radial Runout - A condition where the tire and wheel assembly is slightly out of round forcing the spindle to move up and down as the vehicle rolls along a smooth surface.

Reed Tachometer - A mechanical device that uses reeds to indicate the frequency and magnitude of the vibration.

Resonance - The point where a vibrating component's frequency matches the natural frequency of another component.

Responding Component - The noticeable component that is vibrating.

Road Force - A change in the force between the wheel and the axle while rotating under a load. Discrepancy in road force can cause a vibration although the tire and rim may be perfectly round and the tire is balanced.

Road Force Measurement - A measurement of the wheel assembly as would be found from an actual road test of a vehicle. The GSP9700 Series Vibration Control System is equipped with a load roller to take the Road Force Measurement. The load roller places up to 1400 pounds of force on the spinning tire, and then automatically withdraws from the wheel.

Road Force Variation - A change in force exerted on the axle by the tire/wheel assembly while rotating under load.

Source Component - A component causing another object to vibrate.

Spacer - The accessory used to prevent scratches on the wheel when on the balancer shaft.

Static Balance - A procedure that balances the wheel assembly using only a single weight plane.

TDC - An abbreviation for top dead center. Also referred to as “12 o'clock position.”

Torque Sensitive Vibration - The vibration occurs when accelerating, decelerating, or applying the throttle.
Total Indicated Reading (T.I.R.) - Data measurements taken by the load roller (measured in lbs. or kg) or Dataset® Arms (measured in inches or millimeters) representing the actual runout measured. The T.I.R. data represents the difference in value between the highest and lowest value measured.

Transference Path - The object(s) that transfer the frequency.

Vibration - A shaking or trembling which may be heard or felt.

Wheel Diameter - Dimension measured on the inside of the rim at the bead seats.

Wheel Offset - The measured distance between the mounting face of the wheel and the centerline of the rim.

Wheel Width - Dimension measured on the inside of the rim between the bead seats.