ASTM_F_421_-_15.pdf

Designation:F42115Standard 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.Anumber in parentheses indicates the year of last reapproval.Asuperscriptepsilon()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,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 SI units are to be regarded as thestandard.The values given in parentheses are 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 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 IrregularWear 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 groove,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 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 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 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.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,bounded 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 away.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 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 various1This 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 2013 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 International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 types 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 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-mech