ASTM F1649-96e1
(Test Method)Standard Test Methods for Evaluating Wet Braking Traction Performance of Passenger Car Tires on Vehicles Equipped with Anti-Lock Braking Systems
Standard Test Methods for Evaluating Wet Braking Traction Performance of Passenger Car Tires on Vehicles Equipped with Anti-Lock Braking Systems
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: ( ) a straight-line (rectilinear) "split-[mu]" ([mu] = 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 ( ) 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 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 and health practices and determine the applicability of regulatory limitations prior to use.
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Standards Content (Sample)
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e1
Designation: F 1649 – 96
Standard Test Methods for
Evaluating Wet Braking Traction Performance of Passenger
Car Tires on Vehicles Equipped with Anti-Lock Braking
Systems
This standard is issued under the fixed designation F 1649; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (e) indicates an editorial change since the last revision or reapproval.
e NOTE—Section 3 was updated editorially in April 1998.
INTRODUCTION
These test methods cover procedures for measuring the wet braking performance of passenger car
tires when tested on vehicles equipped with an anti-lock braking system (ABS). ABS operation is
accomplished by the use of wheel rotation rate sensors that detect impending wheel lockup and
controllable 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 to
forestall the lockup and maintain wheel rotation. This process is repeated until the vehicle comes to
a stop. The necessary lateral force to maintain vehicle control in an emergency braking situation is
only possible when wheel rotation is maintained. Although there may be differences in the braking
performance among the commercially available“ vehicle-ABS” combinations, tires may be evaluated
for their relative or comparative wet braking performance with any one “vehicle-ABS-driver”
combination, by the methods as outlined in these test methods.
1. Scope wet traction performance.
1.2 These test methods specify that the wet braking traction
1.1 These test methods cover the measurement of two types
tests be conducted on two specially prepared test courses: (1)
of ABS vehicle behavior that reflect differences in tire wet
a straight-line (rectilinear) “split-μ” (μ 5 friction coefficient)
traction performance when the vehicle is fitted with a series of
test course, with two test lanes deployed along the test course
different tire sets to be evaluated.
(as traveled by the test vehicle); the two lanes have substan-
1.1.1 The stopping distance from some selected speed at
tially different friction levels such that the left pair of wheels
which the brakes are applied.
travels on one surface while the right pair of wheels travels on
1.1.2 The lack of control of the vehicle during the braking
the other surface; and (2) a curved trajectory constant path
maneuver. Uncontrollability occurs when the vehicle does not
radius course with uniform pavement for both wheel lanes.
follow the intended trajectory during the period of brake
1.3 As with all traction testing where vehicle uncontrolla-
application despite a conscious effort on the part of a skilled
bility is a likely outcome, sufficient precautions shall be taken
driver to maintain trajectory control. Uncontrollability is mea-
to protect the driver, the vehicle, and the test site facilities from
sured by a series of parameters related to this deviation from
damage due to vehicle traction breakaway during testing.
the intended trajectory and the motions that the vehicle makes
Standard precautions are roll-bars, secure mounting of all
during the stopping maneuver.
internal instrumentation, driver helmet, and secure seat belt
1.1.3 Although anti-lock braking systems maintain wheel
harness, etc.
rotation and allow for a high degree of trajectory control,
1.4 This standard does not purport to address all of the
different sets of tires with variations in construction, tread
safety concerns, if any, associated with its use. It is the
pattern, and tread compound may influence the degree of
responsibility of the user of this standard to establish appro-
trajectory control in addition to stopping distance. Thus vehicle
priate safety and health practices and determine the applica-
uncontrollability is an important evaluation parameter for tire
bility of regulatory limitations prior to use.
These test methods are under the jurisdiction of ASTM Committee F-9 on Tires
2. Referenced Documents
and are the direct responsibility of Subcommittee F09.20 on Dynamic Response.
2.1 ASTM Standards:
Current edition approved April 10, 1996. Published May 1996. Originally
published as F 1649 – 95. Last previous edition F 1649 – 95.
Copyright © ASTM, 100 Barr Harbor Drive, West Conshohocken, PA 19428-2959, United States.
NOTICE: This standard has either been superceded and replaced by a new version or discontinued.
Contact ASTM International (www.astm.org) for the latest information.
F 1649
E 274 Test Method for Skid Resistance of Paved Surfaces is assumed that test tire set may be substituted for test tire, if a
Using a Full-Scale Tire test tire set is required for the testing.
E 303 Test Method for Measuring Surface Frictional Prop- 3.1.5 candidate tire, n—a test tire that is part of a test
erties Using the British Pendulum Tester program.
E 501 Specification for Standard Rib Tire for Pavement 3.1.5.1 Discussion—The term “candidate object” may be
Skid-Resistance Tests used in the same sense as candidate tire.
E 524 Specification for Standard Smooth Tire for Special- 3.1.6 candidate tire set—a set of candidate tires.
Purpose Pavement Skid-Resistance Tests 3.1.7 reference tire, n—a special tire included in a test
E 965 Test Method for Measuring Surface Macrotexture program; the test results for this tire have significance as a base
Depth Using a Volumetric Technique value or internal benchmark.
E 1136 Specification for a Radial Standard Reference Test 3.1.8 control tire, n—a reference tire used in a specified
Tire manner throughout a test program.
E 1337 Test Method for Determining Longitudinal Peak 3.1.8.1 Discussion—A control tire may be of either type and
Braking Coefficient of Paved Surfaces Using a Standard typical tire use is the reference (control) tire in Practice F 1650
Reference Test Tire that provides algorithms for correcting (adjusting) test data for
F 457 Test Method for Speed and Distance Calibration of a bias trend variations (see Practice F 1650 and Annex A1).
Fifth Wheel Equipped with Either Analog or Digital 3.1.9 surface monitoring tire, n—a reference tire used to
Instrumentation evaluate changes in a test surface over a selected time period.
F 538 Terminology Relating to the Characteristics and Per- 3.1.10 standard reference test tire (SRTT), n—a tire that
formance of Tires meets the requirements of Specification E 1136, commonly
F 1046 Guide for Preparing Artificially Worn Passenger and used as a control tire or a surface monitoring tire.
Light Truck Tires for Testing 3.1.10.1 Discussion—This is a Type 1 reference tire.
F 1650 Practice for Evaluating Tire Traction Performance 3.1.11 stopping distance, n—the path distance (rectilinear or
Data Under Varying Test Conditions curved) needed to bring a vehicle to a stop from some selected
initial brake application speed.
3. Terminology
3.1.12 trajectory, n—the rectilinear or curvilinear path of a
3.1 Definitions of Terms Specific to This Standard: vehicle during a stopping maneuver; it is defined by the center
of gravity and the transient angular orientation of the vehicle.
3.1.1 anti-lock braking system (ABS), n— a collection of
sensing and control hardware installed on a vehicle to prevent 3.1.12.1 intended trajectory, n—the intended or ideal path
(rectilinear or curvilinear) to bring a vehicle to a stop, that is,
wheel lockup during brake application.
3.1.2 test (or testing), n—a procedure performed on an under controlled angular orientation.
3.1.12.2 trajectory guide line (TGL), n—the centerline
object (or set of nominally identical objects) using specified
equipment that produces data unique to the object (or set). marked on the test course pavement that constitutes the
intended trajectory; it is used by the driver to guide or steer the
3.1.2.1 Discussion—Test data are used to evaluate or model
selected properties or characteristics of the object (or set of vehicle on its intended path.
3.1.12.3 orthogonal trajectory deviation, n— the perpen-
objects). The scope of testing depends on the decisions to be
made for any program, and sampling and replication plans (see dicular deviation or distance from the center of the vehicle to
the TGL at the end of a stopping test.
definitions below) need to be specified for a complete program
description. 3.1.13 uncontrollability, n—any deviation of the vehicle
from the intended trajectory (TGL) during or at the end of a
3.1.2.2 test run, n—a single pass of a loaded tire over a
test, or both.
given test surface.
3.1.13.1 plowing, n—in tire testing, a type of uncontrolla-
3.1.2.3 traction test, n—in tire testing, a series of n test runs
bility defined by a loss of steering control with no substantial
at a selected operational condition; a traction test is character-
ized by an average value for the measured performance vehicle yaw; the vehicle moves on a trajectory that is dictated
by vehicle dynamics as determined by velocity, mass, and the
parameter.
3.1.2.4 split-μ test, n—a wet traction or stopping distance available traction at each tire.
3.1.14 yaw, n—in a vehicle, the angular motion of a vehicle
test conducted on a test course with substantially different wet
friction levels for the left and right tire test lanes. about its vertical axis through the center of gravity.
3.1.14.1 yaw velocity, n—the magnitude of the yaw (rota-
3.1.3 test tire, n—a tire used in a test.
3.1.4 test tire set, n—one or more test tires as required by tion or angular displacement); it may be measured by fore and
aft, vehicle vs. pavement, velocity sensors.
the test equipment or procedure, to perform a test, thereby
producing a single test result. 3.1.15 spinout, n—in tire testing, a type of uncontrollability
defined by a loss of steering control due to rapid or substantial
3.1.4.1 Discussion—The four nominally identical tires re-
quired for vehicle stopping distance testing constitute a test tire yaw, or both.
set. In the discussion below where the test tire is mentioned, it
4. Summary of Test Methods
4.1 Methods of Measurement—These test methods are di-
vided into two methods:
Annual Book of ASTM Standards, Vol 04.03.
Annual Book of ASTM Standards, Vol 09.02. 4.1.1 Method A—Rectilinear Trajectory Braking, and
NOTICE: This standard has either been superceded and replaced by a new version or discontinued.
Contact ASTM International (www.astm.org) for the latest information.
F 1649
4.1.2 Method B—Curvilinear Trajectory Braking. permits the ABS to function as intended.
4.1.3 With each method, one of three procedures (Procedure 5.3 The absolute values of the parameters obtained with
1, 2, or 3) that vary in measurement sophistication may be used these test methods are highly dependent upon the characteris-
to evaluate stopping distance and vehicle uncontrollability. tics of the vehicle, the design features of the ABS, the selected
4.1.4 Procedure 1 is the simplest, with manually recorded test pavement(s), and the environmental and test conditions
stopping distance and trajectory deviation measurements. Pro- (for example, ambient temperature, water depths, test speeds)
cedure 2 uses computer data acquisition and non-pavement- at the test course. A change in any of these factors may change
contact sensors to measure speed, stopping distance, and yaw the absolute parameter values and may also change the relative
velocity. Procedure 3 is the most comprehensive; it includes all rating of tires so tested.
the measurement capabilities of Procedure 2 in addition to the 5.4 These test methods are suitable for research and devel-
recording of steering wheel angle throughout the stopping opment purposes where tire sets are compared during a brief
maneuver. The measurement procedures for the performance testing time period. They may not be suitable for regulatory or
parameters are more fully described in Section 11. specification acceptance purposes because the values obtained
4.2 Method A—Rectilinear Trajectory Braking—This mode may not necessarily agree or correlate, either in rank order or
of braking traction testing is conducted by bringing the vehicle absolute value, with those obtained under other conditions (for
to a stop in an intended rectilinear trajectory or straight line example, different locations or different seasonal time periods
motion, on a split-μ test course. The test may be conducted at on the same test course).
a series of initial brake application speeds.
6. Test Vehicle
4.3 Method B—Curvilinear Trajectory Braking—This mode
of braking traction testing is conducted by bringing the vehicle 6.1 Test Vehicle—Any commercially available passenger
vehicle equipped with an ABS may be used for the testing.
to a stop on a curvilinear trajectory (curved path) on a uniform
test surface pavement. The test may be conducted at a series of However, it is important that the same vehicle (same model
year, same version of ABS) be used for all tests in any testing
initial brake application speeds.
program. Different vehicles may give different tire wet traction
NOTE 1—Vehicle uncontrollability may be experienced more abruptly
performance because of their varying handling, suspension,
and with greater frequency with Method B procedures. Therefore, when
and ABS design parameters.
using Method B, precautions should be exercised to avoid any possible
6.1.1 During testing with any selected vehicle, the vehicle
danger during testing. Testing shall begin with the lowest test velocities
selected for any program and as higher velocities are approached, test mass (driver, fuel, and instrumentation load) shall be
sufficient care shall be taken to avoid any danger to the driver, the vehicle,
maintained to a tolerance of 62%.
and any on-site facilities during traction breakaway conditions.
6.1.2 All tests in any program of tire comparisons shall be
NOTE 2—Test speeds lower than 10 km/h are not recommended due to
conducted with the same driver and in the shortest time period
instrumentation insensitivity at this low speed.
possible for any selected test program.
4.4 These test methods contain four annexes and one
6.2 Precautions in ABS Vehicle Use—As with any complex
appendix that give important information to assist in the
test system, certain precautions shall be exercised in any
meaningful evaluation of tire wet traction performance.
testing program. ABS operation efficiency as a function of
4.4.1 Annex A1—Interpretation of Results and Tire Design
brake pad “break-in,” pad operating temperature or fade, or
Feature Evaluation,
both, pad drag, or any other ABS factor (all
...
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