Tire Terminology

The following material was contributed by and is posted with the permission of The Goodyear Tire & Rubber Company in the interest of improving translations related to tire technology.

Goodyear recommends several sources for the language used to describe tires. The first is a book published in 1978 by Goodyear. The author is Frederick J. Kovac and the title is "Tire Technology." Another is a chapter on tires in the "Encyclopedia of Polymer Science and Engineering." The last and maybe the best are two lists used by Goodyear patent attorneys. The lists follow:

1. "Aligning torque"; restoring tire force [?] in slip about the vertical axis at the center of the footprint.
2. "Aspect ratio" of the tire means the ratio of its section height to its section width. "Aspect ratio of the tire means the ratio of its section height to its section width, multiplied by 100% for expression as a percentage.
3. "Axial" and "axially" are used herein to refer to lines or directions that are parallel to the axis of rotation of the tire.
4. "Balance"; uniformity of mass distribution of a tire relative to its spin and steer axis.
5. "Bead" means that part of the tire comprising an annular tensile member wrapped by ply cords and shaped, with or without other reinforcement elements such as flippers, chippers, apexes, toe guards and chafers, to fit the design rim.
6. "Bead unseating"; lateral forces acting to dislodge the tire from the rim.
7. "Belt structure" means at least two annular layers or plies of parallel cords, woven or unwoven, underlying the tread, unanchored to the bead, and having both left and right cords angles in the range from 17・ to 27・with respect to the equatorial plane of the tire.
8. "Bias angle; the angle of cords in a tire with respect to its centerline.
9. "Bias tire" (cross ply); reinforcing cords in carcass ply extend diagonally across the tire from bead to bead at about a 25-50・angle with respect to equatorial plane of the tire . cords run at opposite angles in alternating layers.
10. "Bias belted tire"; tire having a bias angled carcass and a circumferentially restricting belt. The angle of the reinforcing members in the belt in reference to the equatorial plane are bout 5・less than the angle of the reinforcing members of the carcass.
11. "Breakaway"; the point at which a tire suddenly loses road handling ability.
12. "Breakers", refers to at least two annular layers or plies of parallel reinforcement cords having the same angle with reference to the equatorial plane of the tire as the parallel reinforcing cords in carcass plies.
13. "Buckling"; the distortion of the sidewall of a tire while transmitting torque.
14. "Burst"; maximum pressure to which tire can be inflated.
15. "Camber"; tilt of ht front wheels of a vehicle; outward at top is positive.
16. "Carcass" means the tire structure apart from the belt structure, tread, undertread, and sidewall rubber over the plies, but including the beads.
17. "Casing" means the carcass, belt structure, beads, sidewalls, and all other components of the tire excepting the tread and undertread. The casing may be new, unvulcanized rubber or previously vulcanized rubber to be fitted with a new tread.
18. "Caster"; tilt of the support arm of a vehicle; forward at the top is negative.
19. "Chafers"; narrow strips of material placed around the outside of bead to protect cord plies from the rim, distribute flexing about the rim and to seal the tire.
20. "Chipping"; loss of small pieces of tire due to rough terrain (e.g. offroad).
21. "Chunking"; loss of large pieces of tire due to centrifugal forces created at high speed running.
22. "Compensated tread width" means the tread width multiplied by the aspect ratio.
23. "Connicity"; preferential steer of tire.
24. "Cord" means one of the reinforcement strands of which the plies of the tire are comprised.
25. "Cord angle" means the acute angle, left or right in a plan view of the tire, formed by a cord with respect to the equatorial plane. The "cord angle" is measured in a cured but uninflated tire.
26. "Cornering Stiffness"; ratio of rate of change of lateral force v. slip angle.
27. "Dart"; accumulated lag in tire response with sudden release.
28. "Deflection": the reduction in section height of a loaded tire at a given inflation pressure.
29. "Design rim" means a rim having a specified configuration and width.
30. "Design rim width" is the specific commercially available rim width assigned to each tire size and typically is between 70 and 75% of the specific tire's section width.
31. "Drag"; force of road on tire resisting direction of travel.
32. "Draw Bar Pull"; the force between the tire and the ground, usually measured on farm tires by a dynometer vehicle.
33. "Enveloping" ability of tire to absorb road irregularities smaller than the contact patch (footprint).
34. "Equatorial plane (EP)" means the plane perpendicular to the tire's axis of rotation and passing through the center of its tread.
35. "First Harmonic"; the sine curve average of the force variation.
36. "Force Variation"; the differential response of a rolling tie to radial (parallel to wheel plane-equatorial plane) and lateral (perpendicular to wheel plane-axial) stresses.
37. "Footprint" means the contact patch or area of contact of the tire tread with a flat surface at zero speed and under normal load and pressure.
38. "Footprint" means the contact patch or area of contact of the tire tread with a flat surface at zero speed and under normal load and pressure or under specified load, pressure and speed conditions.
39. "Full drop center rim"; one-piece rim with center depression sufficiently deep to permit mounting and dismounting of tire.
40. "Groove" means an elongated void area in a tread that may extend circumferentially or laterally about the tread in a straight curved, or zigzag manner. Circumferentially and laterally extending grooves sometimes have common portions and may be sub classified as "wide", "narrow", or "slot". The slot typically is formed by steel blades inserted into a cast or machined mold or tread ring therefor. In the appended drawings, slots are illustrated by single lines because they are so narrow. A "slot" is a groove having a width in the range from about 0.2% to 0.8% of the compensated tread width, whereas a "narrow groove" has a width in the range from about 0.8% to 3% of the compensated tread width and a "wide groove" has a width greater than 3% thereof. The "groove width" is equal to tread surface area occupied by a groove or groove portion, the width of which is in question, divided by the length of such groove or groove portion; thus, the groove width is its average width over its length. Grooves, as well as other voids, reduce the stiffness of tread regions in which they are located. Slots often are used for this purpose, as are laterally extending narrow or wide grooves. Grooves may be of varying depths in a tire. The depth of a groove may vary around the circumference of the tread, or the depth of one groove may be constant but vary from the depth of another groove in the tire. If such narrow or wide groove are of substantially reduced depth as compared to wide circumferential grooves which they interconnect, they are regarded as forming "tie bars" tending to maintain a rib-like character in the tread region involved.
41. "Growth"; the gradual change of tire size over a period of time due to the effect of inflation pressure and service conditions.
42. "Harshness"; the amount of disturbance transmitted by a tire when it passes over minor but continuous road irregularities.
43. "Hop"; axle disturbance caused by a resonant condition.
44. "Inflection Point" means a point in a curved path at which its direction of curvature changes, that is, the center of curvature shifts from one side of the path to the other. An example of an inflection point is the center of the letter "S".
45. "Inner" means toward the inside of the tire and "outer" means toward its exterior.
46. "Innerliner" means the layer or layers of elastomer or other material that form the inside surface of a tubeless tire and that contain the inflating fluid within the tire.
47. "Joint slap"; response of tire as it passes over discontinuity - e.g. an expansion joint.
48. "Kerfs" "Sipes"; small slots molded into ribs of tire that subdivides the tread surface and improves traction characteristics.
49. "Lateral Pull"; the amount of steering pull from direction of travel.
50. "Lope" vehicle pitching condition resulting from low frequency, high amplitude disturbance.
51. "Lugs"; discontinuous radial rows of tread rubber in direct contact with the road surface.
52. "Nibbling"; the lateral thrust caused by longitudinal discontinuities (such as road edge).
53. "Nonskid"; depth of grooves in a tire tread.
54. "Normal Inflation Pressure" refers to the specific design inflation pressure and load assigned by the appropriate stands organization for the service condition for the tire.
55. "Normal Load" refers to the specific design inflation pressure and load assigned by the appropriate standards organization for the service condition for the tire.
56. "Oversteer"; rear tires having a greater slip angle than the front, thus causing the vehicle to turn more sharply.
57. "Overturning Moment": Lateral force generated when the tire footprint moves outside the center of the wheel.
58. "Pantographing" (Squirm): the tread action caused by its compression in contact with the road and its expansion out of contact with the road.
59. "Pitch": the distance from one peak in the tread pattern to the next.
60. "Pitch tone"; the relative intensity of sound generated in vehicle (from tire) in frequency of 200 Hz.
61. "Plunger strength"; the energy of rupture of a static tire.
62. "Ply"; unless otherwise specified, means a continuous layer of rubber-coated parallel cords.
63. "Ply steer": connicity.
64. "Pneumatic tire": means a laminated mechanical device of generally toroidal shape (usually an open-torus) having beads and a tread and made of rubber, chemicals, fabric and steel or other materials. When mounted on the wheel of a motor vehicle, the tire through its tread provides traction and contains the fluid that sustains the vehicle load.
65. "Power Consumption"; energy required to overcome tire interia
66. "Radial" and "radially" are used to mean directions radially toward or away from the axis of rotation of the tire.
67. "Radial-ply tire" means a belted or circumferentially-restricted pneumatic tire in which the ply cords which extend from bead to bead are laid at cord angles between 65・and 90・with respect to the equatorial plane of ht tire.
68. "Response" time lag from instant driver turns the wheel to the instant tire imparts the signal to the road.
69. "Rib" means a circumferentially extending strip of rubber on the tread which is defined by at least one circumferential "wide groove" and either a second such groove or a lateral edge of the tread, the strip of rubber being laterally undivided by full-depth narrow or wide grooves.
70. "Ridge Effect"; Nibbling.
71. "Rim" means a support for a tire or a tire and tube assembly upon which the tire beads are seated.
72. "Rim Chafing"; damage to bead area caused by movement of tire on rim.
73. "Rolling Radius"; the distance of axle from road surface of moving tire.
74. "Roughness"; ride disturbances due to a tire nonuniformity in the radial direction.
75. "Runout"; the variation in physical dimensions (radius, width) around the tire; a measure of out-of-roundness.
76. "Section height" means the radial distance from the nominal rim diameter to the maximum outer diameter of the tire at the road-contact surface nearest its equatorial plane.
77. "Section height" means the radial distance from the nominal rim diameter to the outer diameter of the tire at its equatorial plane.
78. "Section width" means the maximum linear distance parallel to the axis of the tire and between the exterior of its sidewalls when and after it has been inflated at normal pressure for 24 hours, but unloaded, excluding elevations of the sidewalls due to labeling, decoration or protective bands.
79. "Sectional width Line (SWL)" means a line parallel in the cross-section of the tire to its axis of rotation and which is located at the ire's point of maximum axial width, i.e., at the location at which the tire's section width is measured.
80. "Shake" ride disturbance due to vertical vibration of tire at resonance frequency - 1st harmonic.
81. "Shimmy" abnormal side to side vibration of front wheels.
82. "Sinkage"; compression of soil due to pressure from tire footprint.
83. "Shoulder"; upper portion of sidewall just below tread edge. Effects cornering.
84. "Sidewall" means that portion of a tire between the tread and the bead.
85. "Slip"; differential in magnitude or direction between circumferential velocity of tire at the contact surface and velocity of travel.
86. "Slip Angle"; the direction between the plane of rotation and the direction of travel of tire.
87. "Spring Rate"; the stiffness of tire expressed as the slope of the road deflection curve.
88. "Standing Wave"; a severe distortion of tire components due to high-speed operation.
89. "Static Loaded Radius"; the distance of the axle form the road surface on a stationary tire.
90. "Stiffness"; measure of tires ability to act like a spring.
91. "Suppleness"; flexibility of tire sidewall in the uninflated state.
92. "Tandem"; tires set one immediately behind the other.
93. "Thump"; ride disturbance due to large irregularities in tire.
94. "Tire design load" is the base or reference load assigned to a tire at a specific inflation pressure and service condition; other load-pressure relationships applicable to the tire are based upon that base or reference load.
95. "Torque"; the basic tire function of transmitting force from the drive axle to the ground contact area.
96. "Tramp"; abnormal up and down vibration of front wheels.
97. "Tread" means a molded rubber component which, when bonded to a tire casing, includes that portion of the tire that comes into contact with the road when the tire is normally inflated and under normal load.
98. "Tread Pressure"; the distribution of load across the footprint area of tire.
99. "Tread Radius"; flatness.
100. "Tread Width" means the arc length of the tread surface in the axial direction, that is, in a plane parallel to the axis of rotation of the tire.
101. "Tuber"; machine for extruding rubber for tread or sidewall components (die).
102. "Unit tread pressure" means the radial load borne per unit area (square centimeter or square inch) of the tread surface when that area is in the footprint and the tire is loaded.
103. "Vibration Analysis"; the spectrum of force and noise transmission from the tire to the vehicle.
104. "Warp"; cord in tire fabric that runs lengthwise.
105. "Weft" (filling, pick); light thread placed at right angles to warp.
106. "Waddle-Wobble"; low speed vibrations due to tire nonuniformity that causes the front end of vehicle to sway from side to side.

• "Angle of Incidence" means the angle formed by a line from a ray of light falling on a surface and a perpendicular arising from the point of incidence.
• "Apex" means an elastomeric filler located radially above the bead core and between the plies and the turnup ply.
• "Aspect Ratio" means the ratio of its section height to its section width.
• "Asymmetric tread" means a tread that has a tread pattern not symmetrical about the centerplane or equatorial plane EP of the tire.
• "Axial" and "axially" means the lines or directions that are parallel to the axis of rotation of the tire.
• "Bead" or "Bead Core" means generally that part of the tire comprising an annular tensile member, the radially inner beads are associated with holding the tire to the rim being wrapped by ply cords and shaped, with or without other reinforcement elements such as flippers, chippers, apexes or fillers, toe guards and chafers, the bead or beads under the tread being encapsulated in tread rubber cna be with or without other cord reinforced fabric elements.
• "Belt Structure" or "Reinforcing Belts" means at least two annular layers or plies of parallel cords, woven or unwoven, underlying the tread, unanchored to the bead, and having both left and right cord angles in the range from 17( to 27( with respect to the equatorial plane of the tire.
• "Bias Ply Tire" means that the reinforcing cords in the carcass ply extend diagonally across the tire from bead-to-bead at about a 25-65( angle with respect to the equaotiral plane of the tire, the ply cords running at opposite angles in alternate layers.
• "Bounce" or "Hop" means the vertical acceleration related to first Harmonic Radial Runout or Force Variation of each tire and rim assembly interacting with the other tire and rim assemblies of the vehicle.
• "Carcass" means a laminate of tire ply material and other tire components cut to length suitable for splicing, or already spliced, into a cylindrical or toroidal shape. Additional components may be added to the carcass prior to its being vulcanized to create the molded tire.
• "Casing" means the carcass, belt structure, beads, sidewalls, and all other components of the tire excepting the tread and undertread. The casing may be new, unvulcanized rubber or previously vulcanized rubber to be fitted with a new tread.
• "Chafers" refers to narrow strips of material placed around the outside of the bead to protect cord plies from the rim, distribute flexing above the rim, and to seal the tire.
• "Circumferential" means lines or directions extending along the perimeter of the surface of the annular tire parallel to the Equatorial Plane EP and perpendicular to the axial direction.
• "Cord" means one of the reinforcement strands of which the plies in the tire are comprised.
• "Deflection" means the reduction in section height of a loaded tire at a given inflation pressure.
• "Design Rim" means a rim having a specified configuration and width. For the purposes of this specification, the design rim and design rim width are as specified by the industry standards in effect in the location in which the tire is made. For example, in the United States, the design rims are as specified by the Tire and Rim Association. In Europe, the rims are as specified in the European Tyre and Rim Technical Organization--Standards Manual and the term design rim means the same as the standard measurement rims. In Japan, the standard organization is The Japan Automobile Tire Manufacturer's Association.
• "Design Rim Width" is the specific commercially available rim width assigned to each tire size and typically is between 75% and 90% of the specific tire's section width.
• "Equatorial Plane (EP)" means the plane perpendicular to the tire's axis of rotation and passing through the center of its tread.
• "Footprint" means the contact patch or area of contact of the tire tread with a flat surface at zero speed and under normal load and pressure.
• "Groove" means an elongated void area in a tread that may extend circumferentially or laterally about the tread in a straight, curved, or zigzag manner. Circumferentially and laterally extending grooves sometimes have common portions. The "groove width" is equal to the tread surface area occupied by a groove or groove portion, the width of which is in question, divided by the length of such groove or groove portion; thus, the groove width is its average width over its length. Grooves may be of varying depths in a tire. The depth of a groove may vary around the circumference of the tread, or the depth of one groove may be constant but vary from the depth of another groove in the tire. If such narrow or wide grooves are of substantially reduced depth as compared to wide circumferential grooves which they interconnect, they are regarded as forming "tire bars" tending to maintain a rib-like character in the tread region involved.
• "Inboard side" means the side of the tire nearest the vehicle when the tire is mounted on a wheel and the wheel is mounted on the vehicle.
• "Inner" means toward the inside of the tire and "outer" means twoard its exterior.
• "Innerliner" means the layer or layers of elastomer or other material that form the inside surface of a tubeless tire and that contain the inflating fluid within the tire.
• "Lateral" means an axial direction.
• "Lateral Edge" means the axially outermost edge of the tread as defined by a plane parallel to the equatorial plane and intersecting the outer ends of the axially outermost traction lugs at the radial height of the inner tread surface.
• "Leading" refers to a portion or part of the tread that contacts the ground first, with respect to a series of such parts or portions, during rotation of the tire in the direction of travel.
• "Light deflection" means that as light strikes a surface, the reflected light is angularly directed relative to the angle of incidence of the light source yielding what appears to be a light absorbing characteristic to an observer who is position in general alignment with the light source.
• "Light reflection" means that as light strikes an object, the reflected light is generally aligned with the angle of incidence yielding what appears to be a shiny or reflective characteristic to an observer who is positioned in general alignment with the light source.
• "Lope" means once per revolution fore & aft acceleration/deceleration related to first harmonic radial runout or force variation of tire and rim assembly.
• "Net-to-gross Ratio" means the ratio of the surface area of the normally loaded and normally inflated tire tread rubber that makes contact with a hard flat surface, divided by the area of the tread, including noncontacting portions such as grooves as measured around the entire circumference of the tire.
• "Normal Inflation Pressure" means the specific design inflation pressure assigned by the appropriate standards organization for the service condition for the tire.
• "Normal Load" means the load assigned by the appropriate standards organization for the service condition for the tire when inflated to the normal inflation pressure.
• "Outer" means toward the tire's exterior.
• "Ply" means a continuous layer of rubber-coated parallel cords.
• "Pneumatic tire" means a laminated mechanical device of generally toroidal shape (usually an open-torus) having beads and a tread and made of rubber, chemicals, fabric and steel or other materials. When mounted on the wheel of a motor vehicle, the tire through its tread provides traction and contains the fluid that sustains the vehicle load.
• "Radial" and "radially" mean directions radially toward or away from the axis of rotation of the tire.
• "Radial Ply Tire" means a belted or circumferentially-restricted pneumatic tire in which the ply cords which extend from bead to bead are laid at cord angles between 65( and 90( with respect to the equatorial plane of the tire.
• "Replacement tread" as used herein refers to a premolded and precured tread.
• "Retreading" means the procedure of refurbishing a tread worn tire by removing the old tread and replacing it with a precured tread or a "hot capped" tread.
• "Tread" means a molded rubber component which, when bonded to a tire casing, includes that portion of the tire which comes into contact with the road when the tire is normally inflated and under normal load.
• "Section Height" (SH) means the radial distance from the nominal rim diameter to the outer diameter of the tire at its equatorial plane.
• "Section Width" (SW) means the maximum linear distance parallel to the axis of the tire and between the exterior of its sidewalls when and after it has been inflated at normal pressure for 24 hours, but unloaded, excluding elevations of the sidewalls due to labeling, decoration or protective bands.
• "Shake" means higher frequency lug induced vibration felt in cab or steering wheel or seen in movement of the exhaust stack (no particular acceleration).
• "Shoulder" means the upper portion of sidewall just below the tread edge, tread shoulder or shoulder rib means that portion of the tread near the shoulder.
• "Shudder" means a lug induced vibration at low frequency, resulting in a vertical acceleration felt through the floor of the cab.
• "Sidewall" means that portion of a tire between the tread and the bead.
• "Spring Rate" means the stiffness of the tire as the slope of the load-deflection curve at a given pressure.
• "Subassembly" means an unvulcanized assembly of laminated unreinforced tire components to which a cord reinforced ply or plies and other components can be added to form a tire carcass.
• "Trailing" refers to a portion or part of the tread that contacts the ground last, with respect to a series of such parts or portions during rotation of the tire in the preferred direction of travel.
• "Tramp" means side-to-side motion, or lateral acceleration, induced by first harmonic radial runout or force variation of each tire and rim assembly interacting with each other.
• "Tread" means a molded rubber component which when, bonded to a tire casing, includes that portion of the tire that comes into contact with the road when the tire is normally inflated and under normal load.
• "Tread Arc Width" (TAW) means the width of an arc having its center located on the equatorial plane (EP) and which substantially coincides with the radially outermost surfaces of the various traction elements (lugs, blocks, buttons, ribs, etc.) across the lateral or axial width of the tread portions of a tire when the tire is mounted upon its designated rim and inflated to its specified inflation pressure but not subject to any load.
• "Tread Width" means the arc length of the tread surface in the axial direction, that is, in a plane parallel to the axis of rotation of the tire.
• "Vibration Ratings" means the subjective ride terminology wherein "slight" means barely noticeable; "moderate" means noticeable but not objectionable; "severe" means objectionable.
• "Unit Tread Pressure" means the radial load borne per unit area (square centimeter or square inch) of the tread surface when that area is in the footprint of the normally inflated and normally loaded tire.

Terms added by ISTA from U.S. patents written by native English speakers:

Lay length - the distance along the length of the cord for one of the surrounding strands to make a complete 360 deg. revolution around the outside of the cord

　

Fretting wear - rubbing between adjacent filaments

Taken from US Patent 5358022 to Goodyear:

"Aqua Channel" refers to an extra wide circumferential groove with angled (non parallel), rounded groove walls designed specifically to channel water out of the footprint contact patch of the tire.

"Aspect Ratio" of the tire means the ratio of its section height to its section width.

"Bead" means that part of the tire comprising an annular tensile member wrapped by ply cords and shaped, with or without other reinforcement elements such as flippers, chippers, apexes, toe guards and chafers, to fit the design rim.

"Contact Patch" refers, in footprints separated into two or more portions by wide void areas, to those portions of the footprint that maintain contact with the pavement.

"Carcass" means the tire structure apart from the belt structure, tread, undertread, and sidewall rubber over the plies, but including the beads.

"Crown" refers to the circumferentially outermost portion of the carcass substantially within the width limits of the tread.

"Design Cycle" is a mold manufacturing term that refers to the smallest fundamental unit of tire tread that contains all design features and is continually repeated around the tire with slightly varying lengths according to a specific pitching sequence.

"Design Cycle Pitch" is a mold manufacturing term that refers to the circumferential distance from the beginning boundary of a design cycle to its end and the beginning boundary of the next design cycle.

"Design Net-to-gross" refers to the undeflected tread as designed and molded and is the calculated ratio of the expected ground contacting surface area of the tread, excluding groove void area, to the total expected tread footprint area including the groove void area.

"Design rim" means a rim having a specified configuration and width.

"Directional tread" refers to a tread design which has a preferred direction of rotation in the forward direction of travel.

"Equatorial plane (EP)" means the plane perpendicular to the tire's axis of rotation and passing through the center of its tread.

"Footprint" means the contact patch or area of contact of the tire tread with a flat surface at zero speed and under design load and pressure.

"Footprint Net-to-gross" refers to the actual footprint of a deflected tire and is the ratio of the ground contacting surface area of the tread to the total tread footprint area including the groove void area.

"Groove" means an elongated void area in a tread that may extend circumferentially or laterally about the tread in a straight, curved, or zig-zag manner. Grooves ordinarily remain open in the tire footprint. Circumferentially and laterally extending grooves sometimes have common portions and may be subclassified as "wide" or "narrow". Grooves may be of varying depths in a tire. If such narrow or wide grooves are of substantially reduced depth as compared to wide circumferential grooves which they interconnect, they are regarded as forming "tie bars" tending to maintain a rib-like character in the tread region involved.

"Logarithmic spiral" refers to a spiral that has a gradually expanding arc, as opposed to a substantially constant arc as in for example an Archemedic spiral (i.e. as seen in a phonograph record).

"Lugs" refer to discontinuous radial rows of tread rubber in direct contact with the road surface.

"Net-to-gross" refers to the ratio of the ground contacting surface of a tread to the total tread area.

"Normal load and inflation pressure" refers to the specific design inflation pressure and load assigned by the appropriate standards organization for the design rim and service condition for a tire of specific size. Examples of standards are the Tire and Rim Association Manual and the European Tire and Rim Technical Organization.

"Open angle" refers to a groove wall angle which causes the groove to be wider at the top as compared to its width at the tread base.

"Pitch" refers to the circumferential distance from one design feature in the tread pattern to the next similar design feature.

"Pitch boundary" refers to a substantially lateral line in the circumference of the tire that defines the beginning or end of the pitch. The pitch boundary may sometimes be defined by the center of a lateral groove. A pitch boundary "shift" refers to a circumferential displacement of the line.

"Pitch Tone" refers to a potentially objectionable sound in which the sound energy is concentrated into a narrow frequency band and is perceived essentially as a single frequency that clearly stands out from the surrounding background noise.

"Pneumatic tire" means a laminated mechanical device of generally toroidal shape (usually an open-torus) having beads and a tread and made of rubber, chemicals, fabric and steel or other materials. When mounted on the wheel of a motor vehicle, the tire through its tread provides traction and contains the fluid that sustains the vehicle load.

"Radial" and "radially" are used to mean directions radially toward or away from the axis of rotation of the tire.

"Rib" means a circumferentially extending strip of rubber on the tread which is defined by at least one circumferential "wide groove" and either a second such groove or a lateral edge of the tread, the strip of rubber being laterally undivided by full-depth narrow or wide grooves.

"Shoulder" refers to the upper portion of sidewall just below the tread edge.

"Sidewall" means that portion of a tire between the tread and the bead.

"Sipes" refer to small slots molded into ribs of a tire that subdivide the tread surface and improves traction characteristics. Sipes tend to close completely in a tire footprint.

"Slots" are elongated void areas formed by steel blades inserted into a cast or machined mold or tread ring. Slots ordinarily remain open in a tire footprint. In the appended drawings, slots are illustrated by single lines because they are so narrow.

"Tie-Bar" refers to an extra thickness of rubber at the bottom of a slot such that, in the locations where the extra rubber is present, the slot depth is less than the slot depth at all other locations. Tie-bars stabilize a lug by limiting the independent movement of two portions of a lug that are separated by slots, while traction properties that are inherent
in the use of slots are provided.

"Tread" means a molded rubber component which, when bonded to a tire casing, includes that portion of the tire that comes into contact with the road when the tire is normally inflated and under normal load.

"Tread width" means the arc length of the road contacting tread surface in the axial direction, that is, in a plane parallel to the axis of rotation of the tire.

"Turn-up ply" refers to an end of a carcass ply that wraps around one bead only.

Taken from US Patent 5323596 to Goodyear:

"lay length" as used in connection with a strand in a steel cord is the distance along the length of the strand in which the filament makes a complete 360 deg. revolution around the outside of the strand.
"Cord" means one or more of the reinforcement elements, comprising one or more filaments/wires which may or may not be twisted or otherwise formed, which may further include strands which strands may also be formed, of which the plies in a product are comprised.
"Filament" means an individual metallic wire. "Lay length" means the axial distance required for a filament, strand or layer to make one 360-degree helical revolution in a strand or cord.
"Strand" means a group of filaments combined together to form a unit.
"Twist" means the number of turns about its axis per unit of length in a filament, strand or cord.
"Twist direction" means the slope of the helix of a filament, strand or layer when the cord is held vertically and may be left or right. If the slope of the spirals conforms in direction to the slope of the center portion of the letter "S", then the twist is called "S" or "left-hand". If the slope of the spirals conforms to the slope of the center portion of the letter "Z", then the twist is called "Z" or "right-hand".