ASTM_F_1649_-_13.pdf

Designation:F164913Standard Test Methods forEvaluating Wet Braking Traction Performance of PassengerCar Tires on Vehicles Equipped with Anti-Lock BrakingSystems1This standard is issued under the fixed designation F1649;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.INTRODUCTIONThese test methods cover procedures for measuring the wet braking performance of passenger cartires when tested on vehicles equipped with an anti-lock braking system(ABS).ABS operation isaccomplished by the use of wheel rotation rate sensors that detect impending wheel lockup andcontrollable brake pressure regulators;both of these systems are connected to a control microproces-sor.When potential lockup is detected for any wheel or pair of wheels,brake pressure is lowered toforestall the lockup and maintain wheel rotation.This process is repeated until the vehicle comes toa stop.The necessary lateral force to maintain vehicle control in an emergency braking situation isonly possible when wheel rotation is maintained.Although there may be differences in the brakingperformance among the commercially available“vehicle-ABS”combinations,tires may be evaluatedfor their relative or comparative wet braking performance with any one“vehicle-ABS-driver”combination,by the methods as outlined in these test methods.1.Scope1.1 These test methods cover the measurement of two typesof ABS vehicle behavior that reflect differences in tire wettraction performance when the vehicle is fitted with a series ofdifferent tire sets to be evaluated.1.1.1 The stopping distance from some selected speed atwhich the brakes are applied.1.1.2 The lack of control of the vehicle during the brakingmaneuver.Uncontrollability occurs when the vehicle does notfollow the intended trajectory during the period of brakeapplication despite a conscious effort on the part of a skilleddriver to maintain trajectory control.Uncontrollability is mea-sured by a series of parameters related to this deviation fromthe intended trajectory and the motions that the vehicle makesduring the stopping maneuver.1.1.3 Although anti-lock braking systems maintain wheelrotation and allow for a high degree of trajectory control,different sets of tires with variations in construction,treadpattern,and tread compound may influence the degree oftrajectory control in addition to stopping distance.Thus vehicleuncontrollability is an important evaluation parameter for tirewet traction performance.1.2 These test methods specify that the wet braking tractiontests be conducted on two specially prepared test courses:(1)a straight-line(rectilinear)“split-”(=friction coefficient)test course,with two test lanes deployed along the test course(as traveled by the test vehicle);the two lanes have substan-tially different friction levels such that the left pair of wheelstravels on one surface while the right pair of wheels travels onthe other surface;and(2)a curved trajectory constant pathradius course with uniform pavement for both wheel lanes.1.3 As with all traction testing where vehicle uncontrolla-bility is a likely outcome,sufficient precautions shall be takento protect the driver,the vehicle,and the test site facilities fromdamage due to vehicle traction breakaway during testing.1These test methods are under the jurisdiction ofASTM Committee F09 on Tiresand is the direct responsibility of Subcommittee F09.20 on Vehicular Testing.Current edition approved May 1,2013.Published June 2013.Originallyapproved in 1995.Last previous edition approved in 2003 as F1649 96(2003)which was withdrawn January 2012 and reinstated in May 2013.DOI:10.1520/F1649-13.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 Standard precautions are roll-bars,secure mounting of allinternal instrumentation,driver helmet,and secure seat beltharness,etc.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:2E274 Test Method for Skid Resistance of Paved SurfacesUsing a Full-Scale TireE303 Test Method for Measuring Surface Frictional Proper-ties Using the British Pendulum TesterE501 Specification for Rib Tire for Pavement Skid-Resistance TestsE524 Specification for Smooth Tire for Pavement Skid-Resistance TestsE965 Test Method for Measuring Pavement MacrotextureDepth Using a Volumetric TechniqueE1136 Specification for P195/75R14 Radial Standard Refer-ence Test TireE1337 Test Method for Determining Longitudinal PeakBraking Coefficient of Paved Surfaces Using StandardReference Test TireF45