ASTM_F_1016_-_07_2013e1.pdf

Designation:F101607(Reapproved 2013)1Standard Practice forLinear Tire Treadwear Data Analysis1This standard is issued under the fixed designation F1016;the number immediately following the designation indicates the year oforiginal adoption or,in the case of revision,the year of last revision.A number in parentheses indicates the year of last reapproval.Asuperscript epsilon()indicates an editorial change since the last revision or reapproval.1NOTEEditorial corrections made throughout in June 2013.1.Scope1.1 This practice describes the elementary linear regressionanalysis of basic treadwear data as obtained according to TestMethod F421 and Test Method F762.1.2 The basic treadwear data are obtained as groove depthloss measurements by procedures described in Test MethodF421 after a series of test cycles(test distances under specifiedconditions)according to Test Method F762.1.3 A linear regression analysis is performed for the rela-tionship between average tire tread depth and the test distancetraveled by the test vehicle,on which the test tires are mounted.From this analysis a rate of wear is determined:groove depthloss per unit distance.1.4 Linear treadwear is defined as an essentially constantrate of wear,after break-in,which results in a linear regressioncoefficient of determination,R2,equal to or greater than 0.95when obtained for a data set where the number of measurementintervals,n,is at least 3.Each measurement interval representsa specific test distance.1.5 This practice is not applicable to the prediction oftreadlife for tires that exhibit non-linear or irregular treadwear.1.6 Evaluation parameters are given for both SI and inch-pound units;either may be used.The evaluation parameters asdefined are ones typically used in the tire testing industry andno special claim is made for superiority of these parametersand terms over other terms and parameters that may bedeveloped.2.Referenced Documents2.1 ASTM Standards:2F421 Test Method for Measuring Groove and Void Depth inPassenger Car TiresF538 Terminology Relating to the Characteristics and Per-formance of TiresF762 Test Method for Determining Change in Groove(orVoid)Depth With Distance Traveled for Passenger CarTires3.Terminology3.1 Definitions:3.1.1 average tire tread depth,L,nthe average of all tiregroove(void)depth measurements.F5383.1.2 break-in,L,none or more periods of initial stan-dardized tire operation during which tire is brought to the statewhich will lead to more consistent test results.F5383.1.3 fastest wearing groove,L,nthe circumferentialgroove with the minimum life expectancy.F5383.1.4 fastest wearing location,L,nthat location whichexhibits the highest percent tread(depth)loss as calculated in6.1.1.F5383.1.5 groove,average depth,L,nthe average of all tiregroove depth measurements in a single groove.F5383.1.6 projected treadlife,L,nthe test distance that givesh as the average tread depth;where h is the height of treadwearindicator above groove(or void)base.F5383.1.7 test distance,L,ndistance traveled by a vehicleafter tire break-in.F5384.Summary of Practice4.1 This practice provides a calculation procedure for linearregression analysis of treadwear data to be used in the tireindustry for assessing tire treadwear performance.4.2 No specific mathematical formulas are given for thecustomary least-squares calculations used for linear regressionparameter evaluation since these calculation algorithms arereadily available with electronic hand calculators or statisticalsoftware for personal computers,or both.Terms are defined forslope,intercept,and coefficient of determination.1This practice is under the jurisdiction of ASTM Committee F09 on Tires and isthe direct responsibility of Subcommittee F09.30 on Laboratory(Non-Vehicular)Testing.Current edition approved June 1,2013.Published September 2013.Originallyapproved in 1986.Last previous edition approved in 2007 as F1016 07.DOI:10.1520/F1016-07R13E01.2For 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 5.Significance and Use5.1 The purpose of this practice is to standardize themeaning and derivation of some terms and indexes that arecommonly used to characterize treadwear.5.1.1 There is no intent to recommend either of the twotreadwear performance indexes:distance per unit loss of treaddepth or loss of tread depth per distance unit.6.Calculation6.1 Use the following calculations and terms to reporttreadwear:6.1.1 The percentage tread(depth)loss(PTL)expresses theloss of tread depth as a percent of the initial tread depth(to thetread-depth indicators),as follows:PTL5FXi2 XkXi2 hG3100(1)where:Xi=average tread depth after a break-in(see 3.1.1 or 3.1.2),Xk=average tread depth at a given observation or testdistance(see