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    ASTM F1649 - 20

    Standard Test Methods for Evaluating Wet Braking Traction Performance of Passenger Car Tires on Vehicles Equipped with Anti-Lock Braking Systems

    Active Standard ASTM F1649 | Developed by Subcommittee: F09.20

    Book of Standards Volume: 09.02

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    Significance and Use

    5.1 Braking traction is an important factor in vehicle control especially on wet pavements. These test methods permit an evaluation of tires for their relative or comparative performance on an ABS-equipped vehicle. See Annex A1 for background information for interpretation of results and meaningful evaluation of tire design features for their influence on wet traction performance.

    5.2 Although stopping distance is important for vehicle control, the ability to steer the vehicle on a selected trajectory is equally or, in some instances, more important. The wet traction capability of tires influences both of these measured parameters since the tires are the link between the ABS and the pavement and provide the traction or tire adhesion level that permits the ABS to function as intended.

    5.3 The absolute values of the parameters obtained with these test methods are highly dependent upon the characteristics of the vehicle, the design features of the ABS, the selected test pavement(s), and the environmental and test conditions (for example, ambient temperature, water depths, test speeds) at the test course. A change in any of these factors may change the absolute parameter values and may also change the relative rating of tires so tested.

    5.4 These test methods are suitable for research and development purposes where tire sets are compared during a brief testing time period. They may not be suitable for regulatory or specification acceptance purposes because the values obtained may not necessarily agree or correlate, either in rank order or absolute value, with those obtained under other conditions (for example, different locations or different seasonal time periods on the same test course).

    1. Scope

    1.1 These test methods cover the measurement of two types of ABS vehicle behavior that reflect differences in tire wet traction performance when the vehicle is fitted with a series of different tire sets to be evaluated.

    1.1.1 The stopping distance from some selected speed at which the brakes are applied.

    1.1.2 The lack of control of the vehicle during the braking maneuver. Uncontrollability occurs when the vehicle does not follow the intended trajectory during the period of brake application despite a conscious effort on the part of a skilled driver to maintain trajectory control. Uncontrollability is measured by a series of parameters related to this deviation from the intended trajectory and the motions that the vehicle makes during the stopping maneuver.

    1.1.3 Although anti-lock braking systems maintain wheel rotation and allow for a high degree of trajectory control, different sets of tires with variations in construction, tread pattern, and tread compound may influence the degree of trajectory control in addition to stopping distance. Thus vehicle uncontrollability is an important evaluation parameter for tire wet traction performance.

    1.2 These test methods specify that the wet braking traction tests be conducted on two specially prepared test courses: (1) a straight-line (rectilinear) “split-µ” (µ = friction coefficient) test course, with two test lanes deployed along the test course (as traveled by the test vehicle); the two lanes have substantially different friction levels such that the left pair of wheels travels on one surface while the right pair of wheels travels on the other surface; and (2) a curved trajectory constant path radius course with uniform pavement for both wheel lanes.

    1.3 As with all traction testing where vehicle uncontrollability is a likely outcome, sufficient precautions shall be taken to protect the driver, the vehicle, and the test site facilities from damage due to vehicle traction breakaway during testing. Standard precautions are roll-bars, secure mounting of all internal instrumentation, driver helmet, and secure seat belt harness, etc.

    1.4 The values stated in SI units are to be regarded as the standard. The values given in parenthesis are for information only.

    1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.

    1.6 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.

    2. Referenced Documents (purchase separately) The documents listed below are referenced within the subject standard but are not provided as part of the standard.

    ASTM Standards

    E274 Test Method for Skid Resistance of Paved Surfaces Using a Full-Scale Tire

    E303 Test Method for Measuring Surface Frictional Properties Using the British Pendulum Tester

    E501 Specification for Standard Rib Tire for Pavement Skid-Resistance Tests

    E524 Specification for Standard Smooth Tire for Pavement Skid-Resistance Tests

    E965 Test Method for Measuring Pavement Macrotexture Depth Using a Volumetric Technique

    E1136 Specification for P195/75R14 Radial Standard Reference Test Tire

    E1337 Test Method for Determining Longitudinal Peak Braking Coefficient (PBC) of Paved Surfaces Using Standard Reference Test Tire

    F457 Test Method for Speed and Distance Calibration of Fifth Wheel Equipped With Either Analog or Digital Instrumentation

    F538 Terminology Relating to the Characteristics and Performance of Tires

    F1046 Guide for Preparing Artificially Worn Passenger and Light Truck Tires for Testing

    F1572 Test Methods for Tire Performance Testing on Snow and Ice Surfaces

    F1650 Practice for Evaluating Tire Traction Performance Data Under Varying Test Conditions

    F1805 Test Method for Single Wheel Driving Traction in a Straight Line on Snow- and Ice-Covered Surfaces

    F1806 Practice for Tire Testing Operations-Basic Concepts and Terminology for Reference Tire Use

    F2493 Specification for P225/60R16 97S Radial Standard Reference Test Tire

    ICS Code

    ICS Number Code 43.040.40 (Braking systems); 83.160.10 (Road vehicle tyres)

    UNSPSC Code

    UNSPSC Code 25171702(Automotive braking systems)

    Referencing This Standard
    Link Here
    Link to Active (This link will always route to the current Active version of the standard.)

    DOI: 10.1520/F1649-20

    Citation Format

    ASTM F1649-20, Standard Test Methods for Evaluating Wet Braking Traction Performance of Passenger Car Tires on Vehicles Equipped with Anti-Lock Braking Systems, ASTM International, West Conshohocken, PA, 2020, www.astm.org

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