Manual

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AIR PRESSURE BALANCE &

THRESHOLD PRESSURE TESTS

GENERAL INSTRUCTIONS:

1. Number the axle and each brake on the axle of the vehicle being tested using the illustration.

2. All testing should be performed using both increasing (INC) and decreasing (DEC) air pres-

sure and using our instructions.

3. When performing the Air Brake Pressure Balance Tests the pressure from only one chamber

of a tandem can be used when the same relay valve delivers pressure directly to all four

chambers on the tandem.

4. Record test results in the charts provided.

Air Pressure Balance and

Threshold Pressure Tests

Date: ________________________

Test Conducted By: ____________

Vehicle No: ___________________

Axle No. 1 2 __ __ __ __ __ __ __ __ __ __ __

Brake No.

1 3 __ __ __ __ __ __ __ __ __ __ __

Axle

Brake No.

2 4 __ __ __ __ __ __ __ __ __ __ __

Tractor

Dolly

Trailer TrailerTrailer

Vehicle Manufacturer

Number Model, Year Comments

Tractor

#1 Trailer

Conv. Dolly

#2 Trailer

Conv. Dolly

#3 Trailer

VEHICLE DATA

Summary of content (4 pages)

PAGE 1
AIR PRESSURE BALANCE & THRESHOLD PRESSURE TESTS ® 1 2 __ __ __ __ __ __ __ __ __ __ __ Brake No. 1 3 __ __ __ __ __ __ __ __ __ __ __ 4 __ __ __ __ __ __ __ __ __ __ __ Axle Brake No. 2 Tractor Trailer Dolly Trailer Dolly Trailer VEHICLE DATA Vehicle Number Manufacturer Model, Year Comments 1. Number the axle and each brake on the axle of the vehicle being tested using the illustration. 2.
PAGE 2
Air Brake Pressure Balance Test Service Chamber Pressure at Axle Increasing Pressures for Axle Nos. 1 2 3 4 5 6 Decreasing Pressures for Axle Nos. 7 1 2 3 4 5 5 Trailer Control Line 10 15 20 25 30 40 50 60 Foundation Brake Threshold Pressure Test BR.# INC DEC AVG BR.
PAGE 3
VEHICLE PREPARATION FOR TESTING 1. Adjust all brakes equally using the vehicle manufacturers procedure. 2. Secure the vehicle on a level surface by means other than the brakes and charge the air system to governor cut-out (approximately 120 psi). Shut off engine. CAUTION: To avoid possible injury due to automatic application of the parking brakes during testing, it is recommended that the parking brakes be mechanically caged. 3. Check the vehicle or combination for excessive air system leakage.
PAGE 4
FOUNDATION BRAKE PRESSURE TESTING THRESHOLD Objective: To determine the air pressure required to make and release contact between the lining and drum at each foundation brake on the vehicle. Equipment: Test gauge (use a gauge with a 0-60 psi range.) Important: A low range (0-60 psi) pressure gauge is required for accurate data for the threshold pressure test. Using a higher range (0-100, or 0-150 psi) gauge can result in bad data. Testing: 1.