1、SAE Technical Standards Board Rules provide that: “This report is published by SAE to advance the state of technical and engineering sciences. The use of this report is entirelyvoluntary, and its applicability and suitability for any particular use, including any patent infringement arising therefro
2、m, is the sole responsibility of the user.”SAE reviews each technical report at least every five years at which time it may be reaffirmed, revised, or cancelled. SAE invites your written comments and suggestions.Copyright 2003 Society of Automotive Engineers, Inc.All rights reserved. No part of this
3、 publication may be reproduced, stored in a retrieval system or transmitted, in any form or by any means, electronic, mechanical, photocopying,recording, or otherwise, without the prior written permission of SAE.TO PLACE A DOCUMENT ORDER: Tel: 877-606-7323 (inside USA and Canada)Tel: 724-776-4970 (o
4、utside USA)Fax: 724-776-0790Email: custsvcsae.orgSAE WEB ADDRESS: http:/www.sae.orgSURFACEVEHICLERECOMMENDEDPRACTICEJ225REV.APR2003Issued 1971-01Revised 2003-04Superseding J225 JUN1993Brake Force Distribution Field Test Procedure for Truck and BusForewordThis document has been changed to reflect a f
5、ive-year review and update.1. ScopeThis SAE Recommended Practice provides a field test procedure and instructions for:a. Instrumentation and Equipmentb. Vehicle Preparationc. Test of air-braked single and combination vehiclesd. Calculation of brake force distributione. This test procedure is intende
6、d to be used as a field procedure. If a more refined method, utilizinglaboratory equipment, is required, refer to SAE J1505.1.1 PurposeThis procedure provides a method to determine the brake force distribution (brake systemeffectiveness) for trucks and buses with a GVWR greater than 4536 kg (10 000
7、lb).2. References2.1 Applicable PublicationThe following publication forms a part of this specification to the extent specifiedherein. The latest issue of SAE publications shall apply.2.1.1 SAE PUBLICATIONAvailable from SAE, 400 Commonwealth Drive, Warrendale, PA 15096-0001.SAE J1505Brake Force Dist
8、ribution Test ProcedureTruck and Bus2.2 Related PublicationThe following publication is provided for information purposes only and is not arequired part of this specification.2.2.1 SAE PUBLICATIONAvailable from SAE, 400 Commonwealth Drive, Warrendale, PA 15096-0001.SAE J1626Braking, Stability, and C
9、ontrol Performance Test Procedures for Air- and Hydraulic-BrakeEquipped Trucks, Truck-Tractors and BusesSAE J225 Revised APR2003-2-3. Instrumentation and Equipment3.1 Each vehicle must be equipped with:3.1.1 DECELEROMETER0 to 9.8 m/s2 (0. to 32.2 ft/s2), to measure vehicle deceleration during burnis
10、h or establishIBT.3.1.2 Speedometer, accurate within 1.6 km/h (1 mph) in the range from 32 to 97 km/h (20 to 60 mph).3.1.3 Pressure gage accurate within 1.8 kPa (1/2 psi) in the 69 to 345 kPa (10 to 50 psi) range. Install the gageas follows:3.1.3.1 For single-unit vehicles, pressure gage in the foot
11、 valve circuit with the highest pressure, upstream of anyother valve. This will be the reference gage for the procedure in 5.6.3.1.3.2 For combination vehicles, pressure gage in control line coupling between tractor and first trailer. This willbe the reference gage for the procedure in 5.6.3.1.4 Sto
12、pwatch, 1 s accuracy.3.1.5 Shutoff valves to be installed as follows:3.1.5.1 For single-unit vehicles, the valve to be installed to permit cut-off of front or rear brakes.3.1.5.2 Valve to be installed to permit each axle in the combination to be braked separately.3.1.6 Adjustable pedal stop can be u
13、sed (where conditions permit) to ensure constant application pressures.3.1.7 (Optional) Infrared device to measure initial brake temperature in the range from 38 to 260 C (100 to 500 F).3.1.8 Vehicle axle lifting device and stands used during brake threshold pressure test.3.2 Test should be run on a
14、 dry and flat roadway with no more than a 1% grade in all directions, including crown.3.3 Measure and record ambient temperature and wind conditions, including speed and direction.4. Vehicle Information and Data4.1 Vehicle Information Sheet Test Data Sheet #1 (Figure 1) to be filled in prior to star
15、ting test.4.2 Brake Force Distribution Test Data Sheets #2 and #3 (Figures 2 and 3) to be filled in and used during the testand for calculating brake distribution.5. Vehicle Preparation5.1 Inspect the brake lining and mating surface. Replace if abnormal conditions exist or worn beyondmanufacturers r
16、ecommended limits.5.2 Brakes to be adjusted to manufacturers specifications.5.3 Inspect tires and replace if worn beyond manufacturers recommended limits or abnormal tire condition. Adjusttire pressure per vehicle manufacturers load recommendations.SAE J225 Revised APR2003-3-5.4 Load vehicle to its
17、normal operating capacity, but sufficient load at each axle to prevent brake lock-up below345 kPa (50 psi). Do not exceed the GAWR or GVWR. Record axle weights on Vehicle Information Sheet(Figure 1).5.5 Brakes should be fully seated and free from oil or other contaminants.5.6 Determine the reference
18、 pressure level at which braking starts to occur at each brake by raising the vehicleand rotating the wheel by hand while gradually increasing the input to the brake system. Record the referencepressure level at which brake torque is first evident on the Brake Force Distribution Test Data Sheet (Fig
19、ure 3).Continue to increase pressure to approximately 275 kPa (40 psi) and then slowly release it until the point atwhich no brake drag is detected. Record the reference pressure level at the no-drag point on the Brake ForceDistribution Test Data Sheet (Figure 3). The average of these two recorded v
20、alues is defined as the BrakeThreshold Pressure. Calculate the threshold pressure for each brake and average these values for each axleor tandem set. Threshold pressure should be as close to the same value as possible at each axle.NOTEIf each axle of the tandem set is supplied from different circuit
21、s of the foot valve, an average thresholdpressure should not be used. This could mask a problem on one axle.SAE J225 Revised APR2003-4-FIGURE 1VEHICLE INFORMATION SHEET (TESTS DATA SHEET #1)SAE J225 Revised APR2003-5-FIGURE 2SAE J225 BRAKE FORCE DISTRIBUTION TEST DATA SHEET #2SAE J225 Revised APR200
22、3-6-FIGURE 3SAE J225 BRAKE FORCE DISTRIBUTION FOR CALCULATION TEST DATA SHEET #3SAE J225 Revised APR2003-7-5.7 Temperature ConditioningThe first test of any day should be preceded by a series of five snubs from 64.37to 32.18 km/h (40 to 20 mph) at 1.8 to 2.4 m/s2 (6 to 8 ft/s2) at not less than 1.60
23、 km (1 mile) intervals. In theevent the test is interrupted such that the brakes are allowed to cool to ambient temperature, the conditioningprocess should be repeated prior to resuming test. Using the optional infrared temperature device formeasurement, the braking axle IBT should be within 93 to 1
24、49 C (200 to 300 F) for each brake application.6. Brake Distribution Test6.1 Single-Unit Vehicles6.1.1 TEST PROCEDURES6.1.1.1 Fill out Vehicle Information Data Sheet #1 (Figure 1).6.1.1.2 Temperature condition brakes per 5.7.6.1.1.3 With all brakes operating make three snubs from 48.28 to 32.18 km/h
25、 (30 to 20 mph) at not less than0.80 km (1/2 mile) intervals (transmission in neutral or clutch disengaged) at 69 kPa (10 psi) control linepressure. Record resultant stabilized decelerations on the Brake Force Distribution Test Data Sheet #2(Figure 2). If there is difficulty in reading decelerations
26、 or large variances in decelerations occur, rerun thetest at 103.4 kPa (15 psi). Repeat the three-snub procedure at 137.9, 206.8, and 275.8 kPa (20, 30, and40 psi). Record resultant decelerations.6.1.1.4 By means of the valve installed per 3.1.5.1, shut off the rear brakes and repeat 6.1.1.3.6.1.1.5
27、 Restore the rear brakes to operation and shut off the front brakes. Repeat 6.1.1.3.6.1.1.6 Determine the coastdown time from 48.28 to 40.23 km/h (30 to 25 mph) by accelerating the vehicle to56.32 km/h (35 mph), shift to neutral or declutch with no braking. Measure the time between 48.28 to40.23 km/
28、h (30 and 25 mph) and record on the Brake Force Distribution Test Data Sheet #3 (Figure 3).Calculate the deceleration for each of the coastdown runs using either the Metric or English formula on theBrake Force Distribution Test Data Sheet #3 (Figure 3).NOTEThis must be done in the same direction or
29、directions as the snubs previously were made withrespect to wind and road-grade. Average the four coastdown decelerations. If conditions do notpermit coastdown time test, use 0.01 m/s2 (0.3 ft/s2) as average coastdown deceleration on theBrake Force Distribution Test Data Sheet #2 (Figure 2).6.1.1.7
30、Check data by comparing the sum of decelerations on each axle (corrected for coastdown) with thedecelerations achieved with all axles (corrected for coastdown). Values should be comparable. Rerunportions of test as necessary if discrepancies are large.6.1.1.8 Complete the Brake Force Distribution ca
31、lculation on the Brake Force Distribution Test Data Sheet #3(Figure 3).6.2 Tractor and Semitrailer or Truck and Trailer6.2.1 TEST PROCEDURE6.2.1.1 Proceed through steps 6.1.1.1 and 6.1.1.2.SAE J225 Revised APR2003-8-6.2.1.2 With all brakes operating, make three snubs from 48.28 to 32.18 km/h (30 to
32、20 mph) at not less than0.80 km (1/2 mile) intervals (transmission in neutral or clutch disengaged) at 69 kPa (10 psi) control linepressure. Record resultant stabilized decelerations on the Brake Distribution Test Data Sheet #2(Figure 2). If there is difficulty in reading decelerations or large vari
33、ances in deceleration occur, rerun testat 103.4kPa (15 psi). Repeat the three-snub procedure at 137.9, 206.8, and 275.8 kPa (20, 30, and40psi). Record resultant decelerations.6.2.1.3 By means of the valve installed per 3.1.5.2, shut off the trailer brakes and repeat 6.2.1.2.6.2.1.4 Restore the trail
34、er brakes to operation. Shut off the towing vehicle brakes (or use the trailer brake handvalve if so equipped). Repeat 6.2.1.2.6.2.1.5 Determine coastdown time and make calculations per 6.1.1.6 and 6.1.1.8.6.2.1.6 Check data by comparing the sum of the decelerations on each axle (corrected for coast
35、down) with thedecelerations achieved with all axles (corrected for coastdown). Values should be comparable. Rerunportions of the test as necessary if discrepancies are large.6.2.1.7 Complete the Brake Force Distribution calculation on the Brake Force Distribution Test Data Sheet #3(Figure 3).6.3 Mor
36、e than 5 Axle Combinations6.3.1 Provide jumper hoses or shut off valves, or both, so that each individual axle in the train can be braked byitself from the towing vehicle.6.3.2 TEST PROCEDURE6.3.2.1 Proceed as in 6.2.1 through 6.2.1.7.6.3.2.2 Calculate the brake distribution force for the various ax
37、les in the train using the same mathematicalapproach shown for single-unit and two-unit combinations.NOTEThe Brake Force Distribution Data Sheet does not provide for all the data and calculationsrequired for brake distribution on more than 5 axle combinations. Use separate sheets asrequired.7. Notes
38、7.1 Marginal IndiciaThe change bar (l) located in the left margin is for the convenience of the user in locatingareas where revisions have been made to the previous issue of the report. An (R) symbol to the left of thedocument title indicates a complete revision of the report.PREPARED BY THE SAE TRU
39、CK AND BUS BRAKE SYSTEMS SUBCOMMITTEE OF THESAE TRUCK AND BUS BRAKE COMMITTEESAE J225 Revised APR2003RationaleThis procedure was changed to reflect a 5-year review and update current testing practices.Relationship of SAE Standard to ISO StandardNot applicable.ApplicationThis procedure provides a met
40、hod to determine the brake force distribution (brake systemeffectiveness) for trucks and buses with a GVWR greater than 4536 kg (10 000 lb).Reference SectionSAE J1505Brake Force Distribution Test ProcedureTruck and BusSAE J1626Braking, Stability, and Control Performance Test Procedures for Air- and Hydraulic-BrakeEquipped Trucks, Truck-Tractors and BusesDeveloped by the SAE Truck and Bus Brake Systems SubcommitteeSponsored by the SAE Truck and Bus Brake Committee
