1、Designation: F421 07 (Reapproved 2013)1Standard Test Method forMeasuring Groove and Void Depth in Passenger Car Tires1This standard is issued under the fixed designation F421; the number immediately following the designation indicates the year of originaladoption or, in the case of revision, the yea
2、r of last revision. A number in parentheses indicates the year of last reapproval. A superscriptepsilon () indicates an editorial change since the last revision or reapproval.1NOTEEditorial changes made throughout in June 2013.1. Scope1.1 This test method describes standard procedures formeasuring t
3、he groove and void depth in passenger car tires.1.2 Any mechanical, optical, or electronic device capable ofmeasuring groove (void) depth can be used, but only thecontact methodology is described here. Noncontact methodol-ogy is beyond the scope of this test method.1.3 The values stated in inch-poun
4、d units are to be regardedas the standard. The values given in parentheses are forinformation only.1.4 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety and healt
5、h practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2F538 Terminology Relating to the Characteristics and Per-formance of TiresF1082 Practice for TiresDetermining Precision for TestMethod Standards (Withdrawn 2005)33. Terminol
6、ogy3.1 Definitions:3.1.1 circumferential line, n on a tire, any real or imagi-nary circle on the surface of a tire, lying in a plane that isperpendicular to the spin axis.3.1.2 element, nan isolated (totally bounded by void)projection.3.1.3 groove, na void that is relatively narrow comparedto its le
7、ngth.3.1.4 groove average depth, L, nthe average of all tiregroove depth measurements in a single groove.3.1.5 groove (void) depth, L, na measurement of theperpendicular distance from a real or calculated reference planedefined by edges of two adjacent ribs (lugs) to the lowest pointof contact in th
8、e groove (void).3.1.5.1 DiscussionThe reader is cautioned that the probetip used for the depth measurement must have a sufficientlysmall cross-section compared to the width of the void beingmeasured. The probe must be able to reach the bottom of thevoid without contacting the tread elements that for
9、m the sidesof the void.Special consideration should be given to measuring sipes.(See definition in Terminology F538.) Since the sipe issubstantially narrower than a major groove, a very smalldiameter probe tip must be used to achieve an accuratemeasurement of sipe depth.3.1.6 irregular wear, na type
10、 of treadwear characterizedby substantial variations of tread loss both from projection toprojection and frequently from point to point on a givenprojection.3.1.7 projection, na pavement contacting area of the treadband, bounded by void.3.1.8 rib, na continuous circumferential projection.3.1.9 tread
11、wear indicator, na raised portion of a groovebottom or void bottom that is molded in a tire at fairly regularintervals around the circumference to provide a visual indica-tion that most of a tread has been worn away.3.1.10 uniform wear, na type of treadwear characterizedby equal tread loss both from
12、 projection to projection and frompoint to point on a given projection, resulting in a smoothappearance of all parts of the tread pattern.3.1.11 void, na volume (in the tread band) defined by thelack of rubber, the depth dimension of this volume may varyfrom point to point in (on) the tread band.4.
13、Summary of Test Method4.1 This test method gives the detailed procedures and theneeded precautions for the measurement of the groove or void1This test method is under the jurisdiction of ASTM Committee F09 on Tiresand is the direct responsibility of Subcommittee F09.30 on Laboratory (Non-Vehicular)
14、Testing.Current edition approved June 1, 2013. Published November 2013. Originallyapproved in 1975. Last previous edition approved in 2007 as F421 07. DOI:10.1520/F0421-07R13E01.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org.
15、For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.3The last approved version of this historical standard is referenced onwww.astm.org.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959.
16、 United States1depth of the tread pattern in a tire. Calculations for varioustypes of average groove or void depths are given in addition tothe required nomenclature for effective communication of thegroove or void measurement results.5. Significance and Use5.1 The groove (void) depth affects the ti
17、res ability todevelop tractive forces in various operating environments.Groove (void) depth also defines the state of wear of a tire andis used in the determination of the rate of wear.6. Apparatus6.1 Gauge, meeting the specifications of the AmericanGauge Design Committee.6.1.1 The apparatus shall c
18、onsist of a mechanical or electro-mechanical depth gauge fitted with a foot through which aspindle passes. The foot may have any of a variety of shapes,including but not limited to cylindrical, semi-cylindrical, andrectangular. The reference surface of the foot shall be made ofa non-deformable mater
19、ial, ground planar and perpendicular tothe gauge spindle. Examples of mechanical gauges and typicalavailable gauge feet are illustrated in Figs. 1 and 2. A typicalelectro-mechanical gauge system is illustrated in Fig. 3.6.1.2 The reading of the depth gauge shall be accurate towithin 6 0.001 in. (0.0
20、25 mm) over a range of 1 in. (25 mm).The resolution of the gauge shall be at least 0.001 in. (0.025mm).6.1.3 The gauge spindle shall extend at least 1 in. (25 mm)beyond the reference surface of the foot. Spindles may haveany of a variety of shapes and diameters suitable for the treadto be measured.
21、Two frequently used spindles are illustrated inFig. 4.6.1.4 The spindle shall not touch the side of the hole in thefoot.6.1.5 Zero AdjustmentThe system shall be adjustable tozero when the foot is pressed against a flat surface. Therepeatability on the flat surface shall be within 620 % of onedivisio
22、n (0.0002 in. (0.005 mm).6.1.6 The accuracy shall be to within 0.001 in. (0.025 mm)for distances up to 0.5 in. (12.7 mm) and to within 0.005 in.(0.125 mm) for distances from 0.5 to 1 in. (12.7 to 25 mm).6.1.7 The overall variability for a series of repeated mea-surements on the flat surface shall be
23、 within 620 % of onedivision.6.1.8 Calibration shall be made using gauge blocks withdimensions traceable to the National Institute of Standards andTechnology primary standard.7. Preparation7.1 Gauge Zero AdjustmentPlace the foot of the gaugeagainst a nondeformable flat surface such as a glass plate
24、andadjust dial to zero.7.2 Preparation of Tire:7.2.1 Mount the tire on an approved width rim and inflate tothe required pressure.7.2.2 The tire shall be in temperature equilibrium with theenvironment in which it is measured.NOTE 1For purposes of this test method, temperature equilibriumexists if the
25、 gauge pressure remains within 1 psi (6.9 kPa) of the requiredinflation pressure during the complete measurement process.7.2.3 The tire must be dry and free of any foreign materialthat would interfere with accurate measurement.7.2.4 Avoid the rubber vents on the tread during measure-ment or remove t
26、hem, leaving no projections above the treadsurface.8. Procedure8.1 Tires with Uniform WearPlace the foot of the gauge sothat it bridges adjacent ribs or lugs over the area to bemeasured, avoiding treadwear indicators, and so that thespindle makes perpendicular contact with the groove or voidbottom a
27、s shown in Fig. 1. This single measurement charac-terizes the groove (void) depth at this location.8.2 Tires Exhibiting Irregular WearProceed in accordancewith 8.1, except the spindle does not have to make perpendicu-lar contact at base of groove as shown in Fig. 2.9. Characterization of Groove (Voi
28、d) Depth for theWhole Tire9.1 The depth of a groove (void) of a tire is characterized bythe arithmetic mean of a number of individual measurements.9.2 Location of Measurements on Ribbed Tires:9.2.1 Preferred Method Make measurements on all ribs orin all grooves.9.2.2 Minimum RequirementMake measurem
29、ents on twoouter grooves and on either the center groove or, in the absenceof a center groove, on the two grooves adjacent to thecenterline of the tread.9.3 Location of Measurements on Lug Tires:9.3.1 Tires with Tread Width Greater Than 7 in. (178mm)Locate six or seven circumferential lines equally
30、spacedacross the tread symmetrically arranged around a line at thecenter of the tread. The two outer lines shall be within 1 in. (25mm) of the shoulders.9.3.2 Tires with Tread Width Less Than 7 in. (178 mm)Locate four or five circumferential lines equally spaced acrossFIG. 1 Illustration of Principl
31、e of MethodF421 07 (2013)12the tread symmetrically arranged around a line at the center ofthe tread. The two outer lines shall be within 1 in. (25 mm) ofthe shoulders.9.3.3 Minimum RequirementsProceed in accordance withno restriction on tread width.9.4 Number of Measurements:9.4.1 Preferred MethodTe
32、n equally spaced measurementsaround each rib or circumferential line avoiding treadwearindicators.NOTE 2The measurement should be taken at the nearest point alongthe circumferential line at which a proper measurement can be taken.9.4.2 Minimum RequirementSix equally spaced measure-ments on each rib
33、or circumferential line (Note 2) avoidingtreadwear indicators.9.5 Calculations:9.5.1 Average Groove DepthCalculate the arithmeticmean and standard deviation for all measurements in onegroove.9.5.2 Average Void Depth on a Circumferential LineCalculate the arithmetic mean and standard deviation for al
34、lmeasurements made on one circumferential line.9.5.3 Average Tread DepthCalculate the arithmetic meanusing all measurements made on the tire.9.6 Report:9.6.1 Report the following information:9.6.1.1 Complete tire description,9.6.1.2 Complete rim description,9.6.1.3 Inflation pressure of the tire and
35、 ambient tempera-ture at the time of measurement,9.6.1.4 The complete raw data set, including number ofmeasurements, their arithmetic mean, standard deviation, andlocation,FIG. 2 Irregular Wear Measured Using a Cylindrical FootFIG. 3 Electro-Mechanical Gauge SystemFIG. 4 Cylindrical Foot with Typica
36、l SpindlesF421 07 (2013)139.6.1.5 Gauge description, including foot and pinconfigurations, and9.6.1.6 Method of zero gauge adjustment.9.6.2 The report shall be in columnar form.10. Characterization of a Tire Exhibiting Irregular Wear10.1 The determination of the tire groove (void) depth isfrequently
37、 made in connection with experiments related topredicting the tread life of a tire or in relationship to its tractiveproperties. The occurrence of irregular wear may render the tireunsuitable for the test purpose.10.2 It is beyond the scope of this test method to determinethe manner in which irregul
38、ar wear may relate to definitions oflegal tread depths or to warranty agreements between tirebuyers and sellers.11. Precision and Bias11.1 On the basis of experience with this test method withtires not exhibiting any form of irregular wear, the followingwithin-laboratory single-operator gaging preci
39、sion can be ex-pected. The arithmetic mean of six measurements in a groovewill have a repeatability, r, of approximately 0.004 in. (0.10mm) for repeated measurements of that groove or void. SeePractice F1082 for the definition of repeatability.11.2 No concept of accuracy in the sense of a bias from
40、atrue value is applicable to tire tread measurements. Referencevalues do not exist for this test method, since the value or levelof the test property is exclusively defined by the test method.Bias, therefore, cannot be determined.12. Keywords12.1 depth gauge; groove depth; irregular wear; tread dept
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44、tee on Standards, at the address shown below.This standard is copyrighted by ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959,United States. Individual reprints (single or multiple copies) of this standard may be obtained by contacting ASTM at the aboveaddress or at 610-832-9585 (phone), 610-832-9555 (fax), or serviceastm.org (e-mail); or through the ASTM website(www.astm.org). Permission rights to photocopy the standard may also be secured from the ASTM website (www.astm.org/COPYRIGHT/).F421 07 (2013)14
