1、Designation: E 1337 90 (Reapproved 2002)Standard Test Method forDetermining Longitudinal Peak Braking Coefficient of PavedSurfaces Using a Standard Reference Test Tire1This standard is issued under the fixed designation E 1337; the number immediately following the designation indicates the year ofor
2、iginal adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method covers the measurement of peakbraking coeff
3、icient of paved surfaces using a standard referencetest tire (SRTT) as described in Specification E 1136 thatrepresents current technology passenger car radial tires. Gen-eral test procedures and limitations are presented for determin-ing peak braking coefficient independent of surface conditions.Ac
4、tual surface test conditions are determined and controlled bythe user at the time of test. Test and surface conditiondocumentation procedures and details are specified. This mea-surement quantifies the peak braking coefficient at the time oftest and does not necessarily represent a maximum or fixedv
5、alue.1.2 This test method utilizes a measurement representingthe peak braking force on a braked test tire passing over a roadsurface. This test is conducted with a tire under a nominalvertical load at a constant speed while its major plane isparallel to its direction of motion and perpendicular to t
6、hepavement.1.3 The measured peak braking coefficient obtained with theequipment and procedures stated herein may not necessarilyagree or correlate directly with those obtained by other surfacecoefficient measuring methods.1.4 This standard does not purport to address all of thesafety concerns, if an
7、y, 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:E 274 Test Method for Skid Resistance of Paved Surf
8、acesUsing A Full-Scale Tire2E 556 Test Method for Calibrating a Wheel Force or TorqueTransducer Using a Calibration Platform (User Level)2E 867 Terminology Relating to Traveled Surface Character-istics2E 1136 Specification for a Radial Standard Reference TestTire2F 377 Practice for Calibration of Br
9、aking/Tractive Measur-ing Devices for Testing Tires3F 408 Test Method for Tires for Wet Traction in Straight-Ahead Braking, Using a Towed Trailer3F 457 Method for Speed and Distance Calibration of a FifthWheel Equipped with Either Analog or Digital Instrumen-tation33. Terminology3.1 Definitions:3.1.
10、1 chirp testthe progressive application of brake torquerequired to produce the maximum value of longitudinal brak-ing force that will occur prior to wheel lockup, with subsequentbrake release to prevent any wheel lockup (tire slide).3.1.2 For other definitions pertaining to this standard, seeTermino
11、logy E 867 and Method F 408.3.2 Descriptions of Terms:3.2.1 braking force coeffcient, tirethe ratio of brakingforce to vertical load.3.2.2 braking force coeffcient, tire, peakthe maximumvalue, as defined in 12.2, of tire braking force coefficient thatoccurs prior to wheel lockup as the braking torqu
12、e is progres-sively increased.3.2.3 braking force coeffcient, tire, slidethe value of thebraking force coefficient obtained on a locked wheel.3.2.4 braking force, tirethe negative longitudinal forceresulting from braking torque application.3.2.5 braking torquethe negatively directed wheel torque.3.2
13、.6 longitudinal force, tire (Fx)the component of a tireforce vector in the X8 direction.3.2.7 tire-axis systemthe origin of the tire-axis system isthe center of the tire contact. The X8 axis is the intersection ofthe wheel plane and the road plane with a positive directionforward. The Z8 axis is per
14、pendicular to the road plane with apositive direction downward. The Y8 axis is in the road plane,its direction being chosen to make the axis system orthogonaland right-hand (see Fig. 1 in Method F 408).3.2.8 tire forcesthe external forces acting on the tire bythe road.1This test method is under the
15、jurisdiction of ASTM Committee E17 onVehicle-Pavement Systems and is the direct responsibility of Subcommittee E17.21on Field Methods for Measuring Tire Pavement Friction.Current edition approved Feb. 23, 1990. Published April 1990.2Annual Book of ASTM Standards, Vol 04.03.3Annual Book of ASTM Stand
16、ards, Vol 09.02.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.3.2.9 torque wheel (T)The external torque applied to a tirefrom a vehicle about the wheel spin axis. Driving torque ispositive wheel torque; braking torque is negative w
17、heel torque.3.2.10 vertical load (Fz)the downward vertical compo-nent of force between the tire and the road.4. Summary of Test Method4.1 The measurements are conducted with a standard refer-ence test tire (Specification E 1136) mounted on a test trailertowed by a vehicle. The trailer contains a tra
18、nsducer, instru-mentation, and actuation controls for the braking of the testtire. See 6.6 for trailer instrumentation.4.2 The test apparatus is normally brought to a test speed of40 mph (64 km/h). The brake is progressively applied untilsufficient braking torque results to produce the maximumbrakin
19、g force that will occur prior to wheel lockup. Longitu-dinal force, vertical load, and vehicle speed are recorded withthe aid of suitable instrumentation and data acquisition equip-ment.4.3 The peak braking coefficient of the road surface isdetermined from the ratio of the maximum value of brakingfo
20、rce to the simultaneous vertical load occurring prior to wheellockup as the braking torque is progressively increased.5. Significance and Use5.1 Pavement surfaces have different traction characteris-tics, depending on many factors. Surface texture, bindercontent, usage, environmental exposure, and s
21、urface conditions(that is, wet, dry) are some of the factors.5.2 The measured values represent peak braking coefficientsfor tires of the general type in operation on passenger vehicles,obtained with a towed test trailer on a prescribed road surface,under user defined surface conditions. Such surface
22、 conditionsmay include the water depth used to wet the road surface andthe type of water application method. Variations in theseconditions may influence the test results.6. Apparatus6.1 The apparatus consists of a tow vehicle and test trailer.The vehicle and trailer must comply with all legal requir
23、ementsapplicable to state laws when operated on public roads.6.2 Tow VehicleThe vehicle shall have the capability ofmaintaining a test speed of 40 mph (64 km/h) within 60.5 mph(60.8 km/h) even at maximum level of application of brakingforces.6.3 Test TrailerThe test wheel shall be equipped with asuf
24、ficient braking torque to produce the maximum value ofbraking test wheel longitudinal force at the conditions speci-fied.6.3.1 Each of the trailer wheels shall have a suspensioncapable of holding toe and camber changes to within 60.05with maximum vertical suspension displacements under bothstatic an
25、d dynamic conditions.6.3.2 The rate of brake application shall be sufficient tocontrol the time interval between initial brake application andpeak longitudinal force to be between 0.3 and 0.5 s.6.4 Vertical LoadThe trailer shall be of such a design as toprovide a static load of 10316 15 lbf (4586 6
26、67 N) to the testwheel and on detachable trailers a static down load of 100 to200 lbf (445 to 890 N) at the hitch point.6.5 Tire and RimThe test tire shall be the standardreference test tire (SRTT) for pavement tests, as specified inSpecification E 1136, mounted on a suitable 14 by 6-in. rim.6.5.1 W
27、hen irregular wear or damage results from tests, orwhen wear or usage influences the test results, the use of thetire should be discontinued.6.6 Instrumentation:6.6.1 General Requirements for Measuring SystemTheinstrumentation system shall conform to the following overallrequirements at ambient temp
28、eratures between 40 and 100F (4and 38C):6.6.1.1 Overall system accuracy of 61.5 % of applied loadfrom 200 lbf (890 N) to full scale; for example, at 200 lbf (890N), applied calibration force of the system output shall bedeterminable within 63 lbf (613 N).6.6.1.2 The exposed portions of the system sh
29、all tolerate100 % relative humidity (rain or spray) and all other adverseconditions, such as dust, shock, and vibrations which may beencountered in highway operations.6.6.1.3 Braking ForcesThe braking force measuringtransducer shall measure longitudinal reaction force within arange between 0 and 200
30、0 lbf (0 and 8.9 kN) generated at thetire-pavement interface as a result of brake application. The tireforce-measuring transducer shall be of such design as tomeasure the tire-pavement interface force with minimuminertial effects. Transducers are recommended to provide anoutput directly proportional
31、 to force with hysteresis less than1 % of the applied load, nonlinearity less than 1 % of theapplied load up to the maximum expected loading, andsensitivity to any expected cross-axis loading or torque loadingless than 1 % of the applied load. The force transducer shall bemounted in such a manner as
32、 to experience less than 1 angularrotation with respect to its measuring plane at the maximumexpected loading.6.6.1.4 Vertical LoadThe vertical load measuring trans-ducer shall measure the vertical load at the test wheel duringbrake application. The transducer shall have the same specifi-cations as
33、those described in 6.6.1.3.NOTE 1Other transducer systems may be used to determine peakbraking coefficients if they can be shown to correlate with the force-measuring transducer system with the same overall accuracy.6.6.1.5 Vehicle Speed-Measuring TransducersTransducers such as “fifth wheel” or a fr
34、ee-rolling wheelcoupled tachometer shall provide speed resolution and accu-racy of 61.5 % of the indicated speed or 60.5 mph (60.8km/h), whichever is greater. Output shall be directly viewableby the driver and shall be simultaneously recorded. Fifth wheelsystems shall conform to Method F 457.6.6.1.6
35、 Signal Conditioning and Data AcquisitionAll sig-nal conditioning and recording equipment shall provide linearoutput and shall allow data reading resolution to meet therequirements of 6.6.1.1.6.6.1.7 All strain-gage transducers shall be equipped withresistance shunt calibration resistors or equivale
36、nt that can beconnected before or after test sequences. The calibration signalshall be at least 50 % of the normal vertical load and shall berecorded.E 133726.6.1.8 A digital data acquisition system shall be employedto individually digitize the braking force, vertical load, andvehicle speed analog o
37、utputs. The braking force, vertical load,and test wheel speed input signals to be digitized shall besampled (as close to simultaneous as possible to minimizephase shifting) at 100 samples per second for each channelfrom unfiltered analog signals. Vehicle speed can be analogfiltered, if necessary, to
38、 remove noise since this is a steady-statesignal.NOTE 2Experience indicates that data sampling at 100 samples persecond of unfiltered analog skid trailer data will properly describe thesignificant frequencies. To prevent “aliasing,” caution must be exercisedin digitizing skid trailer data which cont
39、ains any significant frequenciesabove 50 Hz or other types of analog data.7. Hazards7.1 The test vehicle, as well as all attachments to it, shallcomply with all applicable state and federal laws. All necessaryprecautions shall be taken beyond those imposed by laws andregulations to ensure maximum sa
40、fety of operating personneland other traffic. No test shall be made when there is dangerthat dispersed water may freeze on the pavement.8. Preparation of Apparatus8.1 Preparation of Test Tire:8.1.1 Trim the test tires to remove all protuberances in thetread area caused by mold air vents or flashes a
41、t moldjunctions.8.1.2 Test tires should be stored in such a location that theyall have the same ambient temperature prior to testing andshield them from the sun to avoid excessive heating by solarradiation.8.1.3 Mount the test tire on Tire and Rim Association (TRA)recommended rim4(6.5) by using conv
42、entional mountingmethods. Caution: Assure proper bead seating by the use of asuitable lubricant. Excessive use of lubricant should be avoidedto prevent slipping of the tire on the wheel rim.8.1.4 Check the test tires for the specified inflation pressureat ambient temperature (cold), just prior to te
43、sting. The test tireinflation pressure shall be 35 6 0.5 psi. (241 6 3 kPa)9. Calibration9.1 Vehicle SpeedCalibrate the test vehicle speed indica-tor at the test speed by determining the time for traversing atconstant speed a reasonably level and straight, accuratelymeasured pavement of a length app
44、ropriate for the method oftiming. Load the test trailer to its specified operating weight forthis calibration. Record speed variations during a traverse withthe test system. Make a minimum of three runs at each testspeed to complete the calibration. Other methods of equivalentaccuracy may be used. C
45、alibration of a fifth wheel shall beperformed in accordance with Method F 457.10. Conditioning10.1 Pretest Tire Conditioning:10.1.1 Test tire pretest conditioning shall be performed toprecondition all tires prior to initial testing. Pretest condition-ing is to be done only once per tire and prior to
46、 any actual testmeasurements. This process is recommended because the newtire burnish effect may have an influence on the peak brakingcoefficient obtained and to minimize test variability caused bytransient, non-preconditioned, tire braking performance.10.1.2 Pretest tire conditioning shall be condu
47、cted on a dryand level surface. Each tire shall be chirped ten times at 20mph (32 km/h) under test load.10.2 General Test Conditions:10.2.1 The test surface shall be free of loose material orforeign deposits.10.2.2 Do not test when wind conditions interfere withwetted test repeatability. Test result
48、s may be influenced bywind speed, or direction, or both. The magnitude of thisdependence is a function of the water depth, applicationprocedures, and surface wind protection.11. Procedure11.1 Warm up electronic test equipment as required forstabilization.11.2 Install an SRTT (Specification E 1136) i
49、n the testposition of the test trailer. A tire with a similar loaded radiusand high cornering properties should be used on the oppositeside to level the axle and to minimize trailer yaw during braketorque applications.11.3 Check and, if necessary, adjust the test trailer staticweight on the test tire to the specified test load (see 6.4).11.4 Check and adjust tire inflation pressure as requiredimmediately before testing to specified value (see 8.1.4).11.5 When testing on an externally wetted test surface,offset the trailer test wheel sufficiently to prevent “tr
