1、Designation: F 421 07Standard Test Method forMeasuring Groove and Void Depth in Passenger Car Tires1This standard is issued under the fixed designation F 421; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revisio
2、n. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method describes standard procedures formeasuring the groove and void depth in passenger car tires.1.2 Any mechanical,
3、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-pound units are to be regardedas the standard. The values given in paren
4、theses 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 health practices and determine the applica-bility of regulatory limitatio
5、ns prior to use.2. Referenced Documents2.1 ASTM Standards:2F 538 Terminology Relating to the Characteristics and Per-formance of TiresF 1082 Practice for TiresDetermining Precision for TestMethod Standards33. Terminology3.1 Definitions:3.1.1 circumferential line, non a tire, any real or imagi-nary c
6、ircle 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 length.3.1.4 groove average depth, L, nthe average of all tiregroove depth measurement
7、s 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 the groove (void).3.1.5.1 DiscussionThe reader is cautioned that the probetip used for
8、 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 form the sidesof the void.Special consideration should be given to measuring sipes.(See
9、 definition in Terminology F 538.) 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 of treadwear characterizedby substantial variations of tread loss both from projec
10、tion 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 treadwear indicator, na raised portion of a groovebottom or void bottom that is molded i
11、n 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 projection to projection and frompoint to point on a given projection, resulting i
12、n 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. Summary of Test Method4.1 This test method gives the detailed procedures and thenee
13、ded precautions for the measurement of the groove or voiddepth of the tread pattern in a tire. Calculations for varioustypes of average groove or void depths are given in addition to1This test method is under the jurisdiction of ASTM Committee F09 on Tiresand is the direct responsibility of Subcommi
14、ttee F09.30 on Laboratory (Non-Vehicular) Testing.Current edition approved Aug. 1, 2007. Published September 2007. Originallyapproved in 1975. Last previous edition approved in 2000 as F 421 00.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at s
15、erviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.3Withdrawn.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.the required nomenclature for effective c
16、ommunication of thegroove or void measurement results.5. Significance and Use5.1 The groove (void) depth affects the tires ability todevelop tractive forces on wet pavements, snow, and soil, andits ability to resist hydroplaning. Groove (void) depth alsodefines the state of wear of a tire and is use
17、d in thedetermination of the rate of wear.6. Apparatus6.1 Gauge, meeting the specifications of the AmericanGauge Design Committee.6.1.1 The apparatus shall consist of a mechanical or electro-mechanical depth gauge fitted with a foot through which aspindle passes. The foot may have any of a variety o
18、f shapes,including but not limited to cylindrical, semi-cylindrical, andrectangular. The reference surface of the foot shall be made ofa non-deformable material, ground planar and perpendicular tothe gauge spindle. Examples of mechanical gauges and typicalavailable gauge feet are illustrated in Figs
19、. 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. (0.025 mm) over a range of 1 in. (25 mm).The smallest scale division on the gauge shall be at least0.001 in. (0.025 mm).6.1.3 The gauge spindle sha
20、ll 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. 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
21、 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 onedivision (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 wi
22、thin 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 within 620 % of onedivision.6.1.8 Calibration shall be made using gauge blocks withdimensions traceable to the National Institute
23、 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 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
24、.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 gauge pressure remains within 1 psi (6.9 kPa) of the requiredinflation pressure during the complete measurement process.7.2.3 The
25、 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 them, leaving no projections above the treadsurface.8. Procedure8.1 Tires with Uniform WearPlace the foot of the gauge sothat it br
26、idges adjacent ribs or lugs over the area to bemeasured, avoiding treadwear indicators, and so that thespindle makes perpendicular contact with the groove or voidbottom as shown in Fig. 1. This single measurement charac-terizes the groove (void) depth at this location.8.2 Tires Exhibiting Irregular
27、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 (Void) Depth for theWhole Tire9.1 The depth of a groove (void) of a tire is characterized bythe arithmetic mean of a number of individ
28、ual 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 measurements on twoouter grooves and on either the center groove or, in the absenceof a center groove, on the two grooves adjacent to thec
29、enterline 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 spacedacross the tread symmetrically arranged around a line at thecenter of the tread. The two outer lines shall be within 1 in. (
30、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 acrossthe tread symmetrically arranged around a line at the center ofthe tread. The two outer lines shall be within 1 in. (25 mm) ofthe shoulders.FIG. 1 Illustration o
31、f Principle of MethodF4210729.3.3 Minimum RequirementsProceed in accordance withno restriction on tread width.9.4 Number of Measurements:9.4.1 Preferred MethodTen equally spaced measurementsaround each rib or circumferential line avoiding treadwearindicators.NOTE 2The measurement should be taken at
32、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 or circumferential line (Note 2) avoidingtreadwear indicators.9.5 Calculations:9.5.1 Average Groove DepthCalculate the arithmeticmean and s
33、tandard deviation for all measurements in onegroove.9.5.2 Average Void Depth on a Circumferential LineCalculate the arithmetic mean and standard deviation for allmeasurements made on one circumferential line.9.5.3 Average Tread DepthCalculate the arithmetic meanusing all measurements made on the tir
34、e.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 ambient tempera-ture at the time of measurement,9.6.1.4 Number of measurements, their arithmetic mean,standard deviation, and location,9.6
35、.1.5 Gauge description, including foot and pin configu-rations, and9.6.1.6 Method of zero gauge adjustment.FIG. 2 Irregular Wear Measured Using a Cylindrical FootFIG. 3 Electro-Mechanical Gauge SystemFIG. 4 Cylindrical Foot with Typical SpindlesF4210739.6.2 The report shall be in columnar form.10. C
36、haracterization of a Tire Exhibiting Irregular Wear10.1 The determination of the tire groove (void) depth isfrequently 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 tireu
37、nsuitable for the test purpose.10.2 It is beyond the scope of this test method to determinethe manner in which irregular 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 m
38、ethod withtires not exhibiting any form of irregular wear, the followingwithin-laboratory single-operator gaging precision 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 o
39、r void. SeePractice F 1082 for the definition of repeatability.11.2 No concept of accuracy in the sense of a bias from 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 t
40、est method.Bias, therefore, cannot be determined.12. Keywords12.1 depth gauge; groove depth; irregular wear; tread depthASTM International takes no position respecting the validity of any patent rights asserted in connection with any item mentionedin this standard. Users of this standard are express
41、ly advised that determination of the validity of any such patent rights, and the riskof infringement of such rights, are entirely their own responsibility.This standard is subject to revision at any time by the responsible technical committee and must be reviewed every five years andif not revised,
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43、end. If you feel that your comments have not received a fair hearing you shouldmake your views known to the ASTM Committee 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).F421074
