ASTM F538-99

Standard Terminology Relating to the Characteristics and Performance of Tires

SCOPE
1.1 This terminology primarily covers definitions for technical terms that occur in ASTM Committee F-9 standards on the characteristics and performance of tires.
1.2 Definitions for terms that may also be used in other technologies, such as vehicle behavior, are worded to cover both areas.
1.3 When any definition in this terminology (that does not have the limiting phrase) is quoted out of context, editorially insert the limiting phrase " in a tire" after the dash following the term. This will properly limit the field of application of the term and definition.

General Information

• Status: Historical
• Publication Date: 09-Apr-1999
• ICS: 01.040.83 - Rubber and plastics industries (Vocabularies)
• ICS: 83.160.01 - Tyres in general
• Technical Committee: F09 - Tires
• Drafting Committee: F09.94 - Terminology

Relations

• Replaced By: ASTM F538-03 - Standard Terminology Relating to the Characteristics and Performance of Tires
• Effective Date: 01-Dec-2003
• Referred By: ASTM F457-04(2017) - Standard Test Method for Speed and Distance Calibration of Fifth Wheel Equipped With Either Analog or Digital Instrumentation
• Effective Date: 10-Apr-1999
• Referred By: ASTM E1136-19 - Standard Specification for P195/75R14 Radial Standard Reference Test Tire
• Effective Date: 10-Apr-1999
• Referred By: ASTM F762/F762M-08(2020)e1 - Standard Test Method for Determining Change in Groove (or Void) Depth With Distance Traveled for Passenger Car Tires
• Effective Date: 10-Apr-1999
• Referred By: ASTM F421-15(2021) - Standard Test Method for Measuring Groove and Void Depth in Passenger Car Tires
• Effective Date: 10-Apr-1999
• Referred By: ASTM F2803-21 - Standard Test Method for Evaluating Rim Slip Performance of Tires and Wheels
• Effective Date: 10-Apr-1999
• Referred By: ASTM F1035-03(2015) - Standard Practice for Use of Rubber-Cord Pie Disk to Demonstrate the Discernment Capability of a Tire X-ray Imaging System
• Effective Date: 10-Apr-1999
• Referred By: ASTM F551/F551M-16(2022) - Standard Practice for Using a 1.707-m [67.23-in.] Diameter Laboratory Test Roadwheel in Testing Tires
• Effective Date: 10-Apr-1999
• Referred By: ASTM F1426-20 - Standard Practice for Identifying Tire Tread Surface Irregular Wear Patterns Resulting from Tire Use
• Effective Date: 10-Apr-1999
• Referred By: ASTM F1923-21 - Standard Test Method for Tires, Pneumatic, Low Speed, Off Highway
• Effective Date: 10-Apr-1999
• Referred By: ASTM F1805-20 - Standard Test Method for Single Wheel Driving Traction in a Straight Line on Snow- and Ice-Covered Surfaces
• Effective Date: 10-Apr-1999
• Referred By: ASTM F2779-10(2016) - Standard Practice for Commercial Radial Truck-Bus Tires to Establish Equivalent Test Severity Between a 1.707-m (67.23-in.) Diameter Roadwheel and a Flat Surface
• Effective Date: 10-Apr-1999
• Referred By: ASTM F2838-17 - Standard Practice for Accelerated Laboratory Aging of Radial Passenger Car and Light Truck Tires through Load Range E for the Laboratory Generation of Belt Separation
• Effective Date: 10-Apr-1999
• Referred By: ASTM F870-23 - Standard Practice for Tread Footprints of Passenger Car Tires Groove Area Fraction and Dimensional Measurements
• Effective Date: 10-Apr-1999
• Referred By: ASTM F3015-21 - Standard Test Method for Accelerated Laboratory Roadwheel Generation of Belt Separation in Radial Passenger Car and Light Truck Tires through Load Range E
• Effective Date: 10-Apr-1999

Standards Content (Sample)

NOTICE: This standard has either been superceded and replaced by a new version or discontinued.
Contact ASTM International (www.astm.org) for the latest information.
Designation: F 538 – 99
Standard Terminology
Relating to the Characteristics and Performance of Tires
This standard is issued under the fixed designation F 538; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (e) indicates an editorial change since the last revision or reapproval.
1. Scope the rubber surface. F 1364
anti-lock braking system (ABS), n—a collection of sensing
1.1 This terminology primarily covers definitions for tech-
and control hardware installed on a vehicle to prevent wheel
nical terms that occur in ASTM Committee F-9 standards on
lock-up during brake application. F 1649
the characteristics and performance of tires.
average tire tread depth, [L], n—the average of all tire
1.2 Definitions for terms that may also be used in other
groove (void) depth measurements. F 1016
technologies, such as vehicle behavior, are worded to cover
axle efficiency, [nd], n—in a vehicle, the ratio of the sum of the
both areas.
wheel torques at the driven wheels to the product of
1.3 When any definition in this terminology (that does not
driveshaft torque and axle ratio.
have the limiting phrase) is quoted out of context, editorially
balancing, n—a process to correct for heavy or light areas of
insert the limiting phrase in a tire after the dash following the
a tire and wheel assembly. F 1922
term. This will properly limit the field of application of the
bandwidth, [1/ T], n—the range of frequencies within which
term and definition.
certain performance characteristics occur; specific limits
2. Terminology normally apply. F811
bead, n—of a tire, the part of a tire that comes in contact with
2.1 Definitions:
the rim and is shaped to secure the tire to the rim. F 1922,
accelerometer, n—an instrument that senses inertial reaction
F 1923
to measure linear or angular acceleration. F811
bead separation, n—a breakdown of bond between tire
accuracy, n—a measurement concept that describes the degree
components in the bead area. F 1922
of correspondence between an average measured value and
belt, n—in a tire, a breaker that substantially restricts the
an accepted reference or standard value for the object,
carcass in a circumferential direction. F 1922, F 1923
material or phenomenon under test. F 1082
belt separation, n—a breakdown of bonding between the belts
aligning stiffness, [FL/g], n—of a tire, the rate of change of
or plies or tread, or combination thereof. F 1922
tire aligning torque with respect to change in tire slip angle,
bias, n—the difference between the average measured test
usually evaluated at zero slip angle.
result and the accepted reference value; it measures in an
aligning stiffness coefficient, n—of a tire, the ratio of tire
inverse manner the accuracy of a test. F 1082
aligning stiffness to the tire normal force.
black sidewall, n—a sidewall on which only black compounds
aligning torque, [FL], n—of a tire, the component of a tire
comprise the outer visible surface of the tire. F 724
moment vector tending to rotate a tire about the Z8-axis,
block, n—synonym for element. F 1426
positive clockwise when looking in the positive direction of
bottom out, v—to deform a tire by radial load on the tread
the Z8-axis. F 403, F 424
until radial movement of the inside surface is stopped by the
alignment, n—the adjustment of various parts of the vehicle’s
rim or other tire inside surface.
suspension system to ensure proper handling stability and to
braking coefficient, [nd], n—the ratio of the braking force to
minimize abnormal tire treadwear. F 1922
the normal force on a tire.
analysis, n—an act of inspecting the S/H image and associat-
braking force, [F], n—of a tire, the negative longitudinal force
ing this image with a known calibration reference. F 1364
resulting from braking torque application. F 403, F 408
anomaly, n—a change in the strain pattern of the rubber
braking force coefficient, n—of a tire, the ratio of braking
surface of a straining block as a result of applied stress
force to normal force. F 403, F 408
brought about through a change in atmospheric pressure on
braking force coefficient, peak, n—of a tire, the maximum
value of tire braking force coefficient that occurs prior to
wheel lockup as the braking torque is progressively in-
This terminology is under the jurisdiction of ASTM Committee F-9 on Tires
creased. F 403, F 408
and is the direct responsibility of Subcommittee F09.94 on Terminology.
braking force coefficient, slide, n—of a tire, the value of
Current edition approved Apr. 10, 1999. Published May 1999. Originally
e3
published as F 538 – 77. Last previous edition F 538 – 95 . braking force coefficient obtained on a locked wheel.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
NOTICE: This standard has either been superceded and replaced by a new version or discontinued.
Contact ASTM International (www.astm.org) for the latest information.
F 538
F 403, F 408 interdependent conditions. F 1922
2 2
braking torque, [ML /T ], n—of a vehicle, the negative wheel cord, n—in a tire, filament(s) or plied yarns used in making a
torque. F 403, F 408 tire ply. F 1922
2 2
brand, n—of a tire, the name under which one or more tire cornering force, [ML /T ], n—of a tire, the horizontal force
lines are marketed. acting perpendicularly to the instantaneous motion vector of
brand, tire, private, n—a brand name used by a tire seller or the center of contact for a tire operating at a slip angle.
group of sellers who are not manufacturers. cornering force coefficient, [nd], n—the ratio of cornering
break, n—a crack or tear extending into or through the force to the normal force on a tire.
reinforcing material. F 1922 cornering stiffness, [F/g], n—of a tire, the negative of the rate
breaker, n—in a tire, one or more plies under the tread region of change of tire lateral force with respect to change in tire
of a tire that are additional to those which extend from bead slip angle, usually evaluated at zero slip angle.
to bead. cornering stiffness coefficient, n—of a tire, the ratio of tire
break-in, [L], n—one or more periods of initial standardized cornering stiffness to tire normal force.
tire operation during which tire is brought to the state which cornering traction coefficient, n—the ratio of the cornering
will lead to more consistent test results. F 762, F 1016 tractive force vector and normal force.
calibration tire, n—a witness tire designed to provide a fixed cornering traction vector angle, n—the angle between the
or known test value for selected properties. F 1806 resultant cornering traction force vector and the X8 axis.
candidate tire, n—a test tire that is part of a test program. cornering tractive force, (F), n—the vectorial sum of lateral
F 1572, F 1649, F 1650, F 1805, F 1806, F 1922 and longitudinal tractive force components.
candidate tire set, n—a set of candidate tires. F 1572, coverstrip, n—a thin layer of black compound which covers
F 1649, F 1650, F 1805, F 1806 the unexposed white sidewall portion of a finished tire.
caravan, n—for purposes of a tire test, two or more vehicles F 724
running in the same time frame, over the same test course(s), crazing, n—minute, closely grouped, generally superficial
under similar but independent conditions. F 1922 cracks that usually results from light activated oxidation.
carcass, n—of a tire, the part of a tire structure that does not F 724
include the tread and sidewall rubber. critical slip angle, (rad or degree), n—the value of the slip
casing, n—of a tire, a used or treadless tire to which additional angle at the peak lateral force coefficient.
tread rubber may be attached for the purpose of retreading. cross-country track, n—surface not subject to repeated traffic
F 1922 in addition, no roads, routes, well-worn trails or man-made
center of tire contact, n—the intersection of the wheel plane improvements; can consist of tank trails with crushed rock or
and the vertical projection of the spin axis of a wheel onto having large exposed obstacles (rocks, boulders, etc.).
the road plane. F 1922
center rib, n—a rib at or near the circumferential centerline of cupping, n—a type of irregular wear characterized by a
the tread band. F 1426 variation in wear rate that may be periodic (essentially
center row, n—a row located at or near the circumferential cycloidally shaped) around the tread band circumference in
centerline. F 1426 one or more rows; the variation of loss is essentially
center wear, n—a type of irregular wear characterized by a independent of individual projections if the pattern contains
wear rate continuously increasing from shoulder to center of these projections. F 1426
the tread band. F 1426 determination, n—the application of the complete measure-
2 2
centripetal acceleration, [ML /T ], n—of a vehicle, the com- ment procedure to one piece, specimen or object to produce
ponent of the vector acceleration (of a point in a vehicle) one numerical measured value to be used to form an average
perpendicular to the tangent of the path of the point and or median. F 1082
parallel to the road plane. developed footprint length, [L], n—the maximum footprint
chip and tear, n—a special type of irregular wear character- dimension in the circumferential direction of the tire, under
ized by a rough tread surface which may contain cracks, stated conditions of measurement. F 870
abrasion pits or surface ruptures. F 1426 developed footprint width, [L], n—the maximum lateral
circumferential line, n—on a tire, any real or imaginary circle dimension of a tire footprint under stated conditions of
on the surface of a tire, lying in a plane that is perpendicular measurement. F 870
to the spin axis. F 421, F 870 diagonal wear, n—a type of irregular wear characterized by an
clinch strip, n—high-modulus or high-hardness compound increased wear rate region or band oriented transversely
applied between the carcass and the sidewall in the bead area (from shoulder to shoulder) at some non-90° angle with
to reinforce the bead. F 724 respect to the circumferential centerline of the tread band.
control tire, n—a reference tire, used in a specified manner F 1426
throughout a test program F 1572, F 1649, F 1650, driving coefficient, [nd], n—the ratio of the driving force to
F 1805, F 1806, F 1922 the normal force. F 424, F 1805
convoy, n—in tire testing, two or more vehicles running at the driving coefficient, peak[nd], n—the maximum value of the
same time, over the same test course, under the same driving coefficient. F 424
NOTICE: This standard has either been superceded and replaced by a new version or discontinued.
Contact ASTM International (www.astm.org) for the latest information.
F 538
driving force, [F], n—of a tire, the positive longitudinal force system. F811
resulting from the application of driving torque. F 424, heel-toe wear, n—a type of irregular wear characterized by
F 1805 different wear rates at the leading and trailing edges of a
2 2
driving torque, [ML /T ], n—of a wheel, the positive wheel projection (element). F 1426
torque. F 424 ice, dry, n—smooth ice without loose surface materials.
effective rolling radius, n—the ratio of the linear velocity of F 1572, F 1805
the wheel center of the free rolling tire in the X8 direction to inclination angle, n—of a tire, the angle between the Z8-axis
the spin velocity. F 424 and the wheel plane. F 424
element, n—an isolated (totally bounded by void) projection. inflation pressure loss rate, n—rate of change of normalized
F 421, F 762, F 870, F 1426 inflation pressure, determined from the slope of the linear
feathering, n—a type of element irregular wear characterized portion of the log pressure versus time curve. F 1112
by thin strips of rubber extending from the edge of the inner liner, n—of a tire, the innermost layer(s) of a tubeless
element. F 1426 tire that limit(s) diffusion of the inflation medium into the
flange, n—that part of the rim which gives lateral support to carcass.
the tire. intended trajectory, n—the intended or ideal path (rectilinear
flex cracking, n—cracking primarily caused by application of or curvilinear) to bring a vehicle to a stop, that is, under
mechanical stress-strain cycling. F 724 controlled angular orientation. F 1649
footprint area, [L ], n—the gross contact area of a tire that is intermediate rib, n—one or more rib(s) located between the
loaded (under stated conditions) against a smooth flat centerline and the shoulder ribs of the tread band. F 1426
surface. F 870 intermediate row, n—a row located between the circumfer-
free rolling tire, n—a loaded tire rolling without applied ential centerline and the shoulder ribs/rows of the tread band.
driving or braking torque. F 424 F 1426
front end breakaway, n—in cornering vehicle, the point in the inter-projection wear, n—a type of irregular treadwear char-
curved trajectory of a vehicle when it can no longer be acterized by different wear rates on one or more adjacent
maintained on its intended path because of front wheel projections (either transverse or circumferential orientation);
departure toward the outside of the curve. this results in a step-off in tread depth between the adjacent
g, n—a unit of acceleration where 1 g is equal to the projections. F 1426
2 2
acceleration of gravity, 9.8 m/s (32.2 ft/s ). F811 intra-projection wear, n—a type of irregular wear character-
global testing, n—testing conducted at two or more laborato- ized by a different wear rate at two or more locations within
ries or test sites for the purpose of comparing candidate tire a given projection. F 1426
performance at each location for selected characteristic inverse wear rate, [nd], n—the distance traveled by a tire,
properties. E 1806 after break-in, per unit loss in tread depth. F 1016
gravel road, n—two lane, all-weather, occasionally main- irregular wear, n—a type of treadwear characterized by
tained, hard or loose surface (for example, large rock, paved, substantial variations of tread loss both from projection to
crushed rock, gravel) intended for medium-weight, low- projection and frequently from point to point on a given
density traffic, in accordance with the U.S. Federal Highway projection. F 421, F 762, F 1426
Administration. F 1922 juncture, n—the interface between two different tire compo-
grooming, v—in tire testing, mechanically reworking a snow nents or different compounds within the same component.
test surface in order to obtain a surface with more consistent F 724
properties. F 1572, F 1805 juncture cracking, n—a crack w
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