ASTM F421-07(2013)e1

NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
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Designation: F421 − 07(Reapproved 2013)
Standard Test Method for
Measuring Groove and Void Depth in Passenger Car Tires
ThisstandardisissuedunderthefixeddesignationF421;thenumberimmediatelyfollowingthedesignationindicatestheyearoforiginal
adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.Asuperscript
epsilon (´) indicates an editorial change since the last revision or reapproval.
ε NOTE—Editorial changes made throughout in June 2013.
1. Scope 3.1.3 groove, n—a void that is relatively narrow compared
to its length.
1.1 This test method describes standard procedures for
measuring the groove and void depth in passenger car tires. 3.1.4 groove average depth, [L], n—the average of all tire
groove depth measurements in a single groove.
1.2 Any mechanical, optical, or electronic device capable of
3.1.5 groove (void) depth, [L], n—a measurement of the
measuring groove (void) depth can be used, but only the
perpendiculardistancefromarealorcalculatedreferenceplane
contact methodology is described here. Noncontact methodol-
defined by edges of two adjacent ribs (lugs) to the lowest point
ogy is beyond the scope of this test method.
of contact in the groove (void).
1.3 The values stated in inch-pound units are to be regarded
3.1.5.1 Discussion—The reader is cautioned that the probe
as the standard. The values given in parentheses are for
tip used for the depth measurement must have a sufficiently
information only.
small cross-section compared to the width of the void being
1.4 This standard does not purport to address all of the measured. The probe must be able to reach the bottom of the
safety concerns, if any, associated with its use. It is the void without contacting the tread elements that form the sides
responsibility of the user of this standard to establish appro- of the void.
priate safety and health practices and determine the applica- Special consideration should be given to measuring sipes.
bility of regulatory limitations prior to use. (See definition in Terminology F538.) Since the sipe is
substantially narrower than a major groove, a very small
2. Referenced Documents
diameter probe tip must be used to achieve an accurate
measurement of sipe depth.
2.1 ASTM Standards:
F538 Terminology Relating to the Characteristics and Per-
3.1.6 irregular wear, n—a type of treadwear characterized
formance of Tires
by substantial variations of tread loss both from projection to
F1082 Practice for Tires—Determining Precision for Test
projection and frequently from point to point on a given
Method Standards (Withdrawn 2005)
projection.
3.1.7 projection, n—a pavement contacting area of the tread
3. Terminology
band, bounded by void.
3.1 Definitions:
3.1.8 rib, n—a continuous circumferential projection.
3.1.1 circumferential line, n— on a tire, any real or imagi-
3.1.9 treadwear indicator, n—a raised portion of a groove
nary circle on the surface of a tire, lying in a plane that is
bottom or void bottom that is molded in a tire at fairly regular
perpendicular to the spin axis.
intervals around the circumference to provide a visual indica-
3.1.2 element, n—an isolated (totally bounded by void)
tion that most of a tread has been worn away.
projection.
3.1.10 uniform wear, n—a type of treadwear characterized
by equal tread loss both from projection to projection and from
This test method is under the jurisdiction of ASTM Committee F09 on Tires
point to point on a given projection, resulting in a smooth
and is the direct responsibility of Subcommittee F09.30 on Laboratory (Non-
Vehicular) Testing. appearance of all parts of the tread pattern.
Current edition approved June 1, 2013. Published November 2013. Originally
3.1.11 void, n—a volume (in the tread band) defined by the
approved in 1975. Last previous edition approved in 2007 as F421 – 07. DOI:
lack of rubber, the depth dimension of this volume may vary
10.1520/F0421-07R13E01.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
from point to point in (on) the tread band.
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
Standards volume information, refer to the standard’s Document Summary page on
4. Summary of Test Method
the ASTM website.
3 4.1 This test method gives the detailed procedures and the
The last approved version of this historical standard is referenced on
www.astm.org. needed precautions for the measurement of the groove or void
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
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F421 − 07 (2013)
depth of the tread pattern in a tire. Calculations for various 6.1.7 The overall variability for a series of repeated mea-
types of average groove or void depths are given in addition to surements on the flat surface shall be within 620 % of one
the required nomenclature for effective communication of the division.
groove or void measurement results. 6.1.8 Calibration shall be made using gauge blocks with
dimensions traceable to the National Institute of Standards and
5. Significance and Use
Technology primary standard.
5.1 The groove (void) depth affects the tire’s ability to
develop tractive forces in various operating environments. 7. Preparation
Groove (void) depth also defines the state of wear of a tire and
7.1 Gauge Zero Adjustment—Place the foot of the gauge
is used in the determination of the rate of wear.
against a nondeformable flat surface such as a glass plate and
adjust dial to zero.
6. Apparatus
7.2 Preparation of Tire:
6.1 Gauge, meeting the specifications of the American
7.2.1 Mount the tire on an approved width rim and inflate to
Gauge Design Committee.
the required pressure.
6.1.1 The apparatus shall consist of a mechanical or electro-
7.2.2 The tire shall be in temperature equilibrium with the
mechanical depth gauge fitted with a foot through which a
environment in which it is measured.
spindle passes. The foot may have any of a variety of shapes,
including but not limited to cylindrical, semi-cylindrical, and
NOTE 1—For purposes of this test method, temperature equilibrium
rectangular. The reference surface of the foot shall be made of
exists if the gauge pressure remains within 1 psi (6.9 kPa) of the required
inflation pressure during the complete measurement process.
a non-deformable material, ground planar and perpendicular to
the gauge spindle. Examples of mechanical gauges and typical
7.2.3 The tire must be dry and free of any foreign material
available gauge feet are illustrated in Figs. 1 and 2. A typical
that would interfere with accurate measurement.
electro-mechanical gauge system is illustrated in Fig. 3.
7.2.4 Avoid the rubber vents on the tread during measure-
6.1.2 The reading of the depth gauge shall be accurate to
ment or remove the
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