1、Designation: F421 15Standard 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 year of last revision.
2、 A number in parentheses indicates the year of last reapproval. A superscriptepsilon () 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, opt
3、ical, 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 SI units are to be regarded as thestandard. The values given in parentheses are
4、for informationonly.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 limitations prior to
5、 use.2. Referenced Documents2.1 ASTM Standards:2D4483 Practice for Evaluating Precision for Test MethodStandards in the Rubber and Carbon Black ManufacturingIndustriesF538 Terminology Relating to the Characteristics and Per-formance of TiresF1426 Practice for Identifying Tire Tread Surface Irregular
6、Wear Patterns Resulting from Tire Use3. Terminology3.1 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. F5383.1.2 element, nan isolated (totally bounded by void)projection. F5383.1.3 g
7、roove, na void that is relatively narrow comparedto its length. F5383.1.4 groove average depth, L, nthe average of all tiregroove depth measurements in a single groove. F5383.1.5 groove (void) depth, L, na measurement of theperpendicular distance from a real or calculated reference planedefined by e
8、dges 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 the depth measurement must have a sufficientlysmall cross-section compared to the width of the void beingmeasured. The probe must be able to reach
9、the bottom of thevoid without contacting the tread elements that form 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 achiev
10、e an accuratemeasurement of sipe depth. F5383.1.6 irregular wear, na type of treadwear characterizedby substantial variations of tread loss both from projection toprojection and frequently from point to point on a givenprojection. F5383.1.7 projection, na pavement contacting area of the treadband, b
11、ounded by void. F5383.1.8 rib, na continuous circumferential projection. F5383.1.9 treadwear 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 a
12、way. F5383.1.10 uniform wear, na type of treadwear characterizedby equal tread loss both from projection to projection and frompoint to point on a given projection, resulting in a smoothappearance of all parts of the tread pattern. F5383.1.11 void, na volume (in the tread band) defined by thelack of
13、 rubber, the depth dimension of this volume may varyfrom point to point in (on) the tread band. F5384. Summary of Test Method4.1 This test method gives the detailed procedures and theneeded precautions for the measurement of the groove or voiddepth of the tread pattern in a tire. Calculations for va
14、rious1This test method is under the jurisdiction of ASTM Committee F09 on Tiresand is the direct responsibility of Subcommittee F09.30 on Laboratory (Non-Vehicular) Testing.Current edition approved June 1, 2015. Published August 2015. Originallyapproved in 1975. Last previous edition approved in 201
15、3 as F421 07 (2013)1.DOI: 10.1520/F0421-15.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.Copyright ASTM Int
16、ernational, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States1types 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) d
17、epth affects the tires 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:6.1.1 The apparatus shall consist of a mechanical or electro-mechanical de
18、pth 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 material, ground planar and perpendicular tothe gaug
19、e 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 60.025 mm (0.001 in.) over a range of 25 mm (1 in.).The resolut
20、ion of the gauge shall be at least 0.025 mm(0.001 in.).6.1.3 The gauge spindle shall extend at least 25 mm (1 in.)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 inF
21、ig. 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 onedivision (0.005 mm (0.0002 in.).6.1.6 The accuracy shal
22、l be to within 0.025 mm (0.001 in.)for distances up to 12.7 mm (0.5 in.) and to within 0.125 mm(0.005 in.) for distances from 12.7 to 25 mm (0.5 to 1 in.).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 s
23、hall 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 non-deformable flat surface such as a glass plate andadjust dial to zero.7.2 Preparation of Tire:
24、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 gauge pressure remains within 7 kPa (1 psi) of
25、 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 them, leaving no projections above the treadsurfac
26、e.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 as shown in Fig. 1. This single measurement charac
27、-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 (Void) Depth for theWhole Tire9.1 The depth of a groo
28、ve (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 MethodMake measurements on all ribs orin all grooves.9.2.2 Minimum RequirementMake measurements on twoouter grooves and on either the center
29、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 180 mm (7in.)Locate six or seven circumferential lines equally spacedacross the tread symmetrically arranged arou
30、nd a line at thecenter of the tread. The two outer lines shall be within 25 mm(1 in.) of the shoulders.9.3.2 Tires with Tread Width Less Than 180 mm (7 in.)Locate four or five circumferential lines equally spaced acrossFIG. 1 Illustration of Principle of MethodF421 152the tread symmetrically arrange
31、d around a line at the center ofthe tread. The two outer lines shall be within 25 mm (1 in.) ofthe shoulders.9.3.3 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 circumfere
32、ntial 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 or circumferential line (Note 2) avoidingtreadwear indicat
33、ors.9.4.3 Measurement of Treadwear Indicator HeightIf theheight of the treadwear indicators is required, take measure-ments at all of the 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 Dep
34、th on a Circumferential LineCalculate the arithmetic mean and standard deviation for allmeasurements made on one circumferential line.FIG. 2 Irregular Wear Measured Using a Cylindrical FootFIG. 3 Electro-Mechanical Gauge SystemFIG. 4 Cylindrical Foot with Typical SpindlesF421 1539.5.3 Average Tread
35、DepthCalculate the arithmetic meanusing all measurements made on the tire.9.5.4 Treadwear Indicator HeightThe height of treadwearindicators is determined by calculating the difference betweenthe depth from the treads surface to the top of the treadwearindicator, and the depth from the treads surface
36、 to the bottomof the tread groove close to the slope at the base of thetreadwear indicator.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
37、.6.1.4 The complete raw data set, including number ofmeasurements, their arithmetic mean, standard deviation(where appropriate), and location,9.6.1.5 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. Cha
38、racterization 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 tireuns
39、uitable 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.10.3 See Practice F1426 if irregular wear is suspected on thetest tire.1
40、1. 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 precision can be ex-pected. The arithmetic mean of six measurements in a groovewill have a repeatability, r, of approx
41、imately 0.004 in. (0.10mm) for repeated measurements of that groove or void. SeePractice D4483 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 th
42、e 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 depthASTM International takes no position respecting the validity of any patent rights asserted in connection with an
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