ASTM F1649-20
(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
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).
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 a...
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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.
Designation: F1649 − 20
Standard Test Methods for
Evaluating Wet Braking Traction Performance of Passenger
Car Tires on Vehicles Equipped with Anti-Lock Braking
1
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. A number 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 pattern, and tread compound may influence the degree of
trajectorycontrolinadditiontostoppingdistance.Thusvehicle
1.1 These test methods cover the measurement of two types
uncontrollability is an important evaluation parameter for tire
of ABS vehicle behavior that reflect differences in tire wet
wet traction performance.
traction performance when the vehicle is fitted with a series of
1.2 These test methods specify that the wet braking traction
different tire sets to be evaluated.
tests be conducted on two specially prepared test courses: (1)
1.1.1 The stopping distance from some selected speed at
a straight-line (rectilinear) “split-µ” (µ = friction coefficient)
which the brakes are applied.
test course, with two test lanes deployed along the test course
1.1.2 The lack of control of the vehicle during the braking
(as traveled by the test vehicle); the two lanes have substan-
maneuver. Uncontrollability occurs when the vehicle does not
tially different friction levels such that the left pair of wheels
follow the intended trajectory during the period of brake
travels on one surface while the right pair of wheels travels on
application despite a conscious effort on the part of a skilled
the other surface; and (2) a curved trajectory constant path
driver to maintain trajectory control. Uncontrollability is mea-
radius course with uniform pavement for both wheel lanes.
sured by a series of parameters related to this deviation from
the intended trajectory and the motions that the vehicle makes
1.3 As with all traction testing where vehicle uncontrolla-
during the stopping maneuver.
bility is a likely outcome, sufficient precautions shall be taken
1.1.3 Although anti-lock braking systems maintain wheel
to protect the driver, the vehicle, and the test site facilities from
rotation and allow for a high degree of trajectory control,
damage due to vehicle traction breakaway during testing.
different sets of tires with variations in construction, tread
Standard precautions are roll-bars, secure mounting of all
internal instrumentation, driver helmet, and secure seat belt
1
harness, etc.
ThesetestmethodsareunderthejurisdictionofASTMCommitteeF09onTires
and is the direct responsibility of Subcommittee F09.20 on Vehicular Testing.
1.4 The values stated in SI units are to be regarded as the
Current edition approved Oct. 1, 2020. Published October 2020. Originally
standard. The values given in parenthesis are for information
approved in 1995. Last previous edition approved in 2013 as F1649 – 13. DOI:
10.1520/F1649-20. only.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
1
---------------------- Page: 1 ----------------------
F1649 − 20
1.5 This standard does not purport to address all of the 3.1.2.1 Discussion—The term “candidate object” may be
safety concerns, if any, associated with its use. It is the used in the same sense as candidate tire.
responsibility of the user of this standard to establish appro- 3.1.3 candidate tire set, n—a set of candidate tires. F538
priate safety
...
This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
Designation: F1649 − 13 F1649 − 20
Standard Test Methods for
Evaluating Wet Braking Traction Performance of Passenger
Car Tires on Vehicles Equipped with Anti-Lock Braking
1
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. A number 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 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
1
These test methods are under the jurisdiction of ASTM Committee F09 on Tires and is the direct responsibility of Subcommittee F09.20 on Vehicular Testing.
Current edition approved May 1, 2013Oct. 1, 2020. Published June 2013October 2020. Originally approved in 1995. Last previous edition approved in 20032013 as
F1649 – 96 (2003)F1649 – 13. which was withdrawn January 2012 and reinstated in May 2013. DOI: 10.1520/F1649-13.DOI: 10.1520/F1649-20.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
1
---------------------- Page: 1 ----------------------
F1649 − 20
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 a
...
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