ASTM F1649-96(2003)
(Test Method)Standard Test Methods for Evaluating Wet Braking Traction Performance of Passenger Car Tires on Vehicles Equipped with Anti-Lock Braking Systems (Withdrawn 2012)
Standard Test Methods for Evaluating Wet Braking Traction Performance of Passenger Car Tires on Vehicles Equipped with Anti-Lock Braking Systems (Withdrawn 2012)
SIGNIFICANCE AND USE
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.
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.
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.
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).
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 helment, 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 ...
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Designation: F1649 – 96 (Reapproved 2003)
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 F1649; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
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 1.1.3 Although anti-lock braking systems maintain wheel
rotation and allow for a high degree of trajectory control,
1.1 These test methods cover the measurement of two types
different sets of tires with variations in construction, tread
of ABS vehicle behavior that reflect differences in tire wet
pattern, and tread compound may influence the degree of
traction performance when the vehicle is fitted with a series of
trajectorycontrolinadditiontostoppingdistance.Thusvehicle
different tire sets to be evaluated.
uncontrollability is an important evaluation parameter for tire
1.1.1 The stopping distance from some selected speed at
wet traction performance.
which the brakes are applied.
1.2 These test methods specify that the wet braking traction
1.1.2 The lack of control of the vehicle during the braking
tests be conducted on two specially prepared test courses: (1)
maneuver. Uncontrollability occurs when the vehicle does not
a straight-line (rectilinear) “split-µ” (µ=friction coefficient)
follow the intended trajectory during the period of brake
test course, with two test lanes deployed along the test course
application despite a conscious effort on the part of a skilled
(as traveled by the test vehicle); the two lanes have substan-
driver to maintain trajectory control. Uncontrollability is mea-
tially different friction levels such that the left pair of wheels
sured by a series of parameters related to this deviation from
travels on one surface while the right pair of wheels travels on
the intended trajectory and the motions that the vehicle makes
the other surface; and (2) a curved trajectory constant path
during the stopping maneuver.
radius course with uniform pavement for both wheel lanes.
1.3 As with all traction testing where vehicle uncontrolla-
ThesetestmethodsareunderthejurisdictionofASTMCommitteeF09onTires
bility is a likely outcome, sufficient precautions shall be taken
and are the direct responsibility of Subcommittee F09.20 on Vehicular Testing.
toprotectthedriver,thevehicle,andthetestsitefacilitiesfrom
Current edition approved May 10, 2003. Published May 2003. Originally
´1
damage due to vehicle traction breakaway during testing.
approved in 1995. Last previous edition approved in 1996 as F1649–96 . DOI:
10.1520/F1649-96R03.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
F1649 – 96 (2003)
Standard precautions are roll-bars, secure mounting of all 3.1.5 reference tire, n—a special tire included in a test
internal instrumentation, driver helmet, and secure seat belt program;thetestresultsforthistirehavesignificanceasabase
harness, etc. value or internal benchmark.
1.4 This standard does not purport to address all of the 3.1.6 spinout, n—in tire testing, a type of uncontrollability
safety concerns, if any, associated with its use. It is the
defined by a loss of steering control due to rapid or substantial
responsibility of the user of this standard to establish appro- yaw, or both.
priate safety and health practices and determine the applica-
3.1.7 standard reference test tire (SRTT), n—a tire that
bility of regulatory limitations prior to use.
meets the requirements of Specification E1136, commonly
used as a control tire or a surface monitoring tire.
2. Referenced Documents
3.1.7.1 Discussion—This is a Type 1 reference tire.
3.1.8 stopping distance, n—the path distance (rectilinear or
2.1 ASTM Standards:
curved) needed to bring a vehicle to a stop from some selected
E274 Test Method for Skid Resistance of Paved Surfaces
initial brake application speed.
Using a Full-Scale Tire
3.1.9 surface monitoring tire, n—a reference tire used to
E303 Test Method for Measuring Surface Frictional Prop-
evaluate changes in a test surface over a selected time period.
erties Using the British Pendulum Tester
3.1.10 test (or testing), n—a procedure performed on an
E501 Specification for Rib Tire for Pavement Skid-
object (or set of nominally identical objects) using specified
Resistance Tests
equipment that produces data unique to the object (or set).
E524 Specification for Smooth Tire for Pavement Skid-
3.1.10.1 Discussion—Test data are used to evaluate or
Resistance Tests
modelselectedpropertiesorcharacteristicsoftheobject(orset
E965 Test Method for Measuring Pavement Macrotexture
ofobjects).Thescopeoftestingdependsonthedecisionstobe
Depth Using a Volumetric Technique
madeforanyprogram,andsamplingandreplicationplans(see
E1136 Specification for A Radial Standard Reference Test
definitions below) need to be specified for a complete program
Tire
description.
E1337 Test Method for Determining Longitudinal Peak
3.1.10.2 split-µ test, n—a wet traction or stopping distance
Braking Coefficient of Paved Surfaces Using Standard
test conducted on a test course with substantially different wet
Reference Test Tire
friction levels for the left and right tire test lanes.
F457 Test Method for Speed and Distance Calibration of
Fifth Wheel Equipped With Either Analog or Digital 3.1.10.3 test run, n—a single pass of a loaded tire over a
given test surface.
Instrumentation
3.1.10.4 traction test, n—in tire testing, a series of n test
F538 Terminology Relating to the Characteristics and Per-
formance of Tires runs at a selected operational condition; a traction test is
characterized by an average value for the measured perfor-
F1046 Guide for PreparingArtificially Worn Passenger and
mance parameter.
Light Truck Tires for Testing
F1650 Practice for Evaluating Tire Traction Performance 3.1.11 test tire, n—a tire used in a test.
Data Under Varying Test Conditions
3.1.12 test tire set, n—one or more test tires as required by
the test equipment or procedure, to perform a test, thereby
3. Terminology producing a single test result.
3.1.12.1 Discussion—The four nominally identical tires re-
3.1 Definitions of Terms Specific to This Standard:
quiredforvehiclestoppingdistancetestingconstituteatesttire
3.1.1 anti-lock braking system (ABS), n—a collection of
set. In the discussion below where the test tire is mentioned, it
sensing and control hardware installed on a vehicle to prevent
is assumed that test tire set may be substituted for test tire, if a
wheel lockup during brake application.
test tire set is required for the testing.
3.1.2 candidate tire, n—a test tire that is part of a test
3.1.13 trajectory, n—the rectilinear or curvilinear path of a
program.
vehicle during a stopping maneuver; it is defined by the center
3.1.2.1 Discussion—The term “candidate object” may be
of gravity and the transient angular orientation of the vehicle.
used in the same sense as candidate tire.
3.1.13.1 intended trajectory, n—the intended or ideal path
3.1.3 candidate tire set—a set of candidate tires.
(rectilinear or curvilinear) to bring a vehicle to a stop, that is,
3.1.4 control tire, n—a reference tire used in a specified
under controlled angular orientation.
manner throughout a test program.
3.1.13.2 orthogonal trajectory deviation, n—the perpen-
3.1.4.1 Discussion—Acontroltiremaybeofeithertypeand
dicular deviation or distance from the center of the vehicle to
typical tire use is the reference (control) tire in Practice F1650
the TGL at the end of a stopping test.
that provides algorithms for correcting (adjusting) test data for
3.1.13.3 trajectory guide line (TGL), n—the centerline
bias trend variations (see Practice F1650 and Annex A1).
marked on the test course pavement that constitutes the
intendedtrajectory;itisusedbythedrivertoguideorsteerthe
vehicle on its intended path.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
3.1.14 uncontrollability, n—any deviation of the vehicle
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
from the intended trajectory (TGL) during or at the end of a
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. test, or both.
F1649 – 96 (2003)
3.1.14.1 plowing, n—in tire testing, a type of uncontrolla- 5. Significance and Use
bility defined by a loss of steering control with no substantial
5.1 Brakingtractionisanimportantfactorinvehiclecontrol
vehicle yaw; the vehicle moves on a trajectory that is dictated
especially on wet pavements. These test methods permit an
by vehicle dynamics as determined by velocity, mass, and the
evaluation of tires for their relative or comparative perfor-
available traction at each tire.
mance on an ABS-equipped vehicle. See Annex A1 for
3.1.15 yaw, n—in a vehicle,theangularmotionofavehicle
background information for interpretation of results and mean-
about its vertical axis through the center of gravity.
ingful evaluation of tire design features for their influence on
3.1.15.1 yaw velocity, n—the magnitude of the yaw (rota-
wet traction performance.
tion or angular displacement); it may be measured by fore and
5.2 Although stopping distance is important for vehicle
aft, vehicle vs. pavement, velocity sensors.
control, the ability to steer the vehicle on a selected trajectory
is equally or, in some instances, more important. The wet
4. Summary of Test Methods
traction capability of tires influences both of these measured
4.1 Methods of Measurement—These test methods are di-
parameterssincethetiresarethelinkbetweentheABSandthe
vided into two methods:
pavement and provide the traction or tire adhesion level that
4.1.1 Method A—Rectilinear Trajectory Braking, and
permits the ABS to function as intended.
4.1.2 Method B—Curvilinear Trajectory Braking.
5.3 The absolute values of the parameters obtained with
4.1.3 Witheachmethod,oneofthreeprocedures(Procedure
these test methods are highly dependent upon the characteris-
1,2,or3)thatvaryinmeasurementsophisticationmaybeused
tics of the vehicle, the design features of theABS, the selected
to evaluate stopping distance and vehicle uncontrollability.
test pavement(s), and the environmental and test conditions
4.1.4 Procedure 1 is the simplest, with manually recorded
(for example, ambient temperature, water depths, test speeds)
stopping distance and trajectory deviation measurements. Pro-
at the test course.Achange in any of these factors may change
cedure 2 uses computer data acquisition and non-pavement-
theabsoluteparametervaluesandmayalsochangetherelative
contact sensors to measure speed, stopping distance, and yaw
rating of tires so tested.
velocity.Procedure3isthemostcomprehensive;itincludesall
5.4 These test methods are suitable for research and devel-
the measurement capabilities of Procedure 2 in addition to the
opment purposes where tire sets are compared during a brief
recording of steering wheel angle throughout the stopping
testing time period.They may not be suitable for regulatory or
maneuver. The measurement procedures for the performance
specification acceptance purposes because the values obtained
parameters are more fully described in Section 11.
may not necessarily agree or correlate, either in rank order or
4.2 Method A—Rectilinear Trajectory Braking—This mode
absolute value, with those obtained under other conditions (for
ofbrakingtractiontestingisconductedbybringingthevehicle
example, different locations or different seasonal time periods
to a stop in an intended rectilinear trajectory or straight line
on the same test course).
motion, on a split-µ test course. The test may be conducted at
a series of initial brake application speeds.
6. Test Vehicle
4.3 MethodB—CurvilinearTrajectoryBraking—Thismode
ofbrakingtractiontestingisconductedbybringingthevehicle
6.1 Test Vehicle—Any commercially available passenger
to a stop on a curvilinear trajectory (curved path) on a uniform
vehicle equipped with an ABS may be used for the testing.
testsurfacepavement.Thetestmaybeconductedataseriesof
However, it is important that the same vehicle (same model
initial brake application speeds.
year, same version ofABS) be used for all tests in any testing
program.Differentvehiclesmaygivedifferenttirewettraction
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
using Method B, precautions should be exercised to avoid any possible and ABS design parameters.
danger during testing. Testing shall begin with the lowest test velocities
6.1.1 During testing with any selected vehicle, the vehicle
selected for any program and as higher velocities are approached,
test mass (driver, fuel, and instrumentation load) shall be
sufficientcareshallbetakentoavoidanydangertothedriver,thevehicle,
maintained to a tolerance of 62%.
and any on-site facilities during traction breakaway conditions.
NOTE 2—Test speeds lower than 10 km/h are not recommended due to 6.1.2 All tests in any program of tire comparisons shall be
instrumentation insensitivity at this low speed.
conducted with the same driver and in the shortest time period
possible for any selected test program.
4.4 These test methods contain four annexes and one
appendix that give important information to assist in the 6.2 Precautions in ABS Vehicle Use—As with any complex
meaningful ev
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