AIR BRAKES - GENERAL INFORMATION
data includes the owners name, model, serial number,
and GVWR for both the tractor and trailer. All of this
information (except the owners name) can be obtained
from the certification labels.
PRESSURE BALANCE AND PRESSURE
BUILD-UP RATE (TIMING) TEST
Conditions: This test is performed on the combination
vehicle (tractor-trailer) with wheels blocked, parking
brake released and air system fully charged.
Connect two test hoses to a duplex gauge.
Connect the hoses from the duplex gauge to the
combination vehicle (Figure 26) as follows:
One hose to the left service brake chamber
on the tractors rearmost axle. The gauge
from this connection will be used as a
reference for comparing pressure and
timing differences with other axles.
The remaining hose to the left service
chamber on the trallers rearmost axle.
NOTE-- If unused chamber ports do not exist, It will be
necessary to disconnect the service brake hose, Install a
tee fitting between the service brake hose and chamber
(Figure 27), and then connect the test hose to the
remaining opening In the tee fitting. 3. Check pressure
balance as follows: While observing the duplex gauge,
slowly apply the service brakes in increments of 34 kPa
from 34 to 207 kPa (5 psi from 5 to 30 psi) and
increments of 138 kPa from 207 to 621 kPa (20 psi from
30 to 90 psi)
Figure 26 - Test Connectlon8 - Single Trailer
CTS-4154Y - Page 29