AIR BRAKES - GENERAL INFORMATION
REFINED SPLIT AIR SYSTEM
Changes in the FMVSS 121 regulations made it possible
to change the air system to what is called the "refined"
split air system.
The refined split air system can be identified by the quick
release valve (Figure 2) in both primary and secondary
service brake systems as well as the parking brake
system. The primary system will not always be at the
Figure 3 - 4x2 Truck With Initial Split Air System
CTS-4154Y - Page 3