ASTM F421-15

Standard Test Method for Measuring Groove and Void Depth in Passenger Car Tires

SIGNIFICANCE AND USE
5.1 The groove (void) depth affects the tire’s ability to develop tractive forces in various operating environments. Groove (void) depth also defines the state of wear of a tire and is used in the determination of the rate of wear.
SCOPE
1.1 This test method describes standard procedures for measuring the groove and void depth in passenger car tires.  
1.2 Any mechanical, optical, or electronic device capable of measuring groove (void) depth can be used, but only the contact methodology is described here. Noncontact methodology is beyond the scope of this test method.  
1.3 The values stated in SI units are to be regarded as the standard. The values given in parentheses are for information only.  
1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.

General Information

• Status: Historical
• Publication Date: 31-May-2015
• ICS: 83.160.10 - Road vehicle tyres
• Technical Committee: F09 - Tires
• Drafting Committee: F09.30 - Laboratory (Non-Vehicular) Testing

Standards Content (Sample)

NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Contact ASTM International (www.astm.org) for the latest information
Designation: F421 − 15
Standard Test Method for
1
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. F538
1.1 This test method describes standard procedures for
3.1.4 groove average depth, [L], n—the average of all tire
measuring the groove and void depth in passenger car tires.
groove depth measurements in a single groove. F538
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 SI units are to be regarded as the
3.1.5.1 Discussion—The reader is cautioned that the probe
standard. The values given in parentheses are for information
tip used for the depth measurement must have a sufficiently
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
2
2.1 ASTM Standards:
measurement of sipe depth. F538
D4483 Practice for Evaluating Precision for Test Method
3.1.6 irregular wear, n—a type of treadwear characterized
Standards in the Rubber and Carbon Black Manufacturing
by substantial variations of tread loss both from projection to
Industries
projection and frequently from point to point on a given
F538 Terminology Relating to the Characteristics and Per-
projection. F538
formance of Tires
3.1.7 projection, n—a pavement contacting area of the tread
F1426 Practice for Identifying Tire Tread Surface Irregular
band, bounded by void. F538
Wear Patterns Resulting from Tire Use
3.1.8 rib, n—a continuous circumferential projection. F538
3. Terminology
3.1.9 treadwear indicator, n—a raised portion of a groove
3.1 Definitions:
bottom or void bottom that is molded in a tire at fairly regular
3.1.1 circumferential line, n— on a tire, any real or imagi-
intervals around the circumference to provide a visual indica-
nary circle on the surface of a tire, lying in a plane that is
tion that most of a tread has been worn away. F538
perpendicular to the spin axis. F538
3.1.10 uniform wear, n—a type of treadwear characterized
3.1.2 element, n—an isolated (totally bounded by void)
by equal tread loss both from projection to projection and from
projection. F538
point to point on a given projection, resulting in a smooth
appearance of all parts of the tread pattern. F538
1 3.1.11 void, n—a volume (in the tread band) defined by the
This test method is under the jurisdiction of ASTM Committee F09 on Tires
and is the direct responsibility of Subcommittee F09.30 on Laboratory (Non-
lack of rubber, the depth dimension of this volume may vary
Vehicular) Testing.
from point to point in (on) the tread band. F538
Current edition approved June 1, 2015. Published August 2015. Originally
ɛ1
approved in 1975. Last previous edition approved in 2013 as F421 – 07 (2013) .
4. Summary of Test Method
DOI: 10.1520/F0421-15.
2
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
4.1 This test method gives the detailed procedures and the
contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
needed precautions for the measurement of the groove or void
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. depth of the tread pattern in a tire. Calculations for various
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
1

---------------------- Page: 1 ----------------------
F421 − 15
types of average groove or void depths are given in addition to 6.1.7 The overall varia
...

This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
´1
Designation: F421 − 07 (Reapproved 2013) F421 − 15
Standard Test Method for
1
Measuring Groove and Void Depth in Passenger Car Tires
This standard is issued under the fixed designation F421; 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 (´) indicates an editorial change since the last revision or reapproval.
1
ε NOTE—Editorial changes made throughout in June 2013.
1. Scope
1.1 This test method describes standard procedures for measuring the groove and void depth in passenger car tires.
1.2 Any mechanical, optical, or electronic device capable of measuring groove (void) depth can be used, but only the contact
methodology is described here. Noncontact methodology is beyond the scope of this test method.
1.3 The values stated in inch-poundSI units are to be regarded as the standard. The values given in parentheses are for
information only.
1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility
of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory
limitations prior to use.
2. Referenced Documents
2
2.1 ASTM Standards:
D4483 Practice for Evaluating Precision for Test Method Standards in the Rubber and Carbon Black Manufacturing Industries
F538 Terminology Relating to the Characteristics and Performance of Tires
F1082F1426 Practice for Tires—Determining Precision for Test Method StandardsIdentifying Tire Tread Surface Irregular Wear
Patterns Resulting from Tire Use (Withdrawn 2005)
3. Terminology
3.1 Definitions:
3.1.1 circumferential line, n— on a tire, any real or imaginary circle on the surface of a tire, lying in a plane that is perpendicular
to the spin axis. F538
3.1.2 element, n—an isolated (totally bounded by void) projection. F538
3.1.3 groove, n—a void that is relatively narrow compared to its length. F538
3.1.4 groove average depth, [L], n—the average of all tire groove depth measurements in a single groove.
3.1.4 groove average depth, [L], n—the average of all tire groove depth measurements in a single groove. F538
3.1.5 groove (void) depth, [L], n—a measurement of the perpendicular distance from a real or calculated reference plane defined
by edges of two adjacent ribs (lugs) to the lowest point of contact in the groove (void).
1
This test method is under the jurisdiction of ASTM Committee F09 on Tires and is the direct responsibility of Subcommittee F09.30 on Laboratory (Non-Vehicular)
Testing.
Current edition approved June 1, 2013June 1, 2015. Published November 2013August 2015. Originally approved in 1975. Last previous edition approved in 20072013
ɛ1
as F421 – 07.F421 – 07 (2013) . DOI: 10.1520/F0421-07R13E01.10.1520/F0421-15.
2
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
3.1.5.1 Discussion—
The reader is cautioned that the probe tip used for the depth measurement must have a sufficiently small cross-section compared
to the width of the void being measured. The probe must be able to reach the bottom of the void without contacting the tread
elements that form the sides of the void.
Special consideration should be given to measuring sipes. (See definition in Terminology F538.) Since the sipe is substantially
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
1

---------------------- Page: 1 ----------------------
F421 − 15
narrower than a major groove, a very small diameter probe tip must be used to achieve an accurate measurement of sipe depth.
F538
3.1.6 irregular wear, n—a type of treadwear characterized by substantial variations of tread loss both from projection to
projection and frequently from point to point on a given projection. F538
3.1.7 projection, n—a pavement contacting area of the tread band, bounded by void. F538
3.1.8 rib, n—a continuous circumferential projection. F538
3.1.9 treadwear indicator, n—a raised portion of a groove bottom or void bottom that is molded in a tire at fairly regular
intervals around the circumference to provide a visual indication that most of a tread has been worn away. F538
3.1.10 uniform wear, n—a type of treadwear characterized
...