What is the difference between spring brake and service brake chambers?
On a T30 brake can, there are two chambers - the service
chamber, and the emergency chamber. In the brake chamber, there is
a spring.. when decompressed, it rotates the S-cam to lock the
brakes. This is your parking brake. When you release the brakes,
the emergency chamber remains constantly supplied with air to
compress this spring, effectively releasing your brakes. The
service chamber counteracts this, allowing you to utilize your
brakes, but only when air is supplied to it when you push on the
treadle valve.