ASTM F421-07

NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
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Designation: F421 − 07
StandardTest Method for
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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.
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
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measurement of sipe depth.
2.1 ASTM Standards:
3.1.6 irregular wear, n—a type of treadwear characterized
F538 Terminology Relating to the Characteristics and Per-
formance of Tires by substantial variations of tread loss both from projection to
projection and frequently from point to point on a given
F1082 Practice for Tires—Determining Precision for Test
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projection.
Method Standards (Withdrawn 2005)
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
point to point on a given projection, resulting in a smooth
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This test method is under the jurisdiction of ASTM Committee F09 on Tires appearance of all parts of the tread pattern.
and is the direct responsibility of Subcommittee F09.30 on Laboratory (Non-
3.1.11 void, n—a volume (in the tread band) defined by the
Vehicular) Testing.
lack of rubber, the depth dimension of this volume may vary
Current edition approved Aug. 1, 2007. Published September 2007. Originally
approved in 1975. Last previous edition approved in 2000 as F421 – 00. DOI:
from point to point in (on) the tread band.
10.1520/F0421-07.
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For referenced ASTM standards, visit the ASTM website, www.astm.org, or
4. Summary of Test Method
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
4.1 This test method gives the detailed procedures and the
the ASTM website.
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needed precautions for the measurement of the groove or void
The last approved version of this historical standard is referenced on
www.astm.org. depth of the tread pattern in a tire. Calculations for various
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F421 − 07
types of average groove or void depths are given in addition to 6.1.7 The overall variability for a series of repeated mea-
the required nomenclature for effective communication of the
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