BRAKES - AIR
TRUCK SERVICE MANUAL
STOPMASTER II WEDGE BRAKE
Once a condition exists of worn linings and the adjusting
bolt is totally extended, continued braking will result in a
The Stopmaster II Wedge brake now incorporates a
series of design changes based on the original
Periodic inspection in accordance with the recommended
preventive maintenance is necessary to retain maximum
If the original adjusting sleeve (actuator) which does not
have the new counterbore (has internal threads the full
length) is to be used, do not employ the adjusting bolt
retainer (snap) ring. Use of the retainer (snap) ring with
the old style adjusting sleeve (actuator) and new style
adjusting bolt would prevent the adjusting bolt from
moving outward and making the necessary lining wear
In addition, the adjusting bolt now has a machined
smooth wiping surface under the head to accept a new
single lip plunger seal.
Major design improvements have been made in four
Single Lip Plunger Seal
general areas of the brake: (1) The automatic adjusting
The adjusting assembly also employs a new single lip
assembly; (2) The adjusting pawl assembly; (3) The
plunger seal to provide more protection for the bolt
non-pressure half of the air chamber; and (4) The brake
threads and improved sealing for the actuation housing
shoe and drum.
components. The lip of this seal wipes against the
AUTOMATIC ADJUSTING BOLT ASSEMBLY
smooth machined surface beneath the head of the bolt.
Limited Travel Adjusting Bolt
The automatic adjusting assembly for the Stopmaster II
employs a limited travel adjusting bolt which cannot over
adjust or cock when the brake lining has been extremely
This seal is designed to allow more flexibility and will
provide additional protection for the adjusting assembly
when the bolt is extended outward in brake application.
Thus, this will reduce the possibility of the adjusting bolt
freezing, due to any corrosion or dirt inside the actuation
This is accomplished with the addition of a snap ring at
the foot of the bolt and a redesigned adjusting sleeve
(actuator) and plunger.
The adjusting sleeve has been counterbored on the I.D.
to accept the redesigned adjusting bolt.
Thus, when the lining Is worn, the counterbored shoulder
of the adjusting sleeve stops the bolt from advancing
further. Consequently, the bolt is prevented from over
To accommodate these changes, the I.D. of the
adjusting plunger has also been counterbored to make
room for the snap ring.
To protect the plunger seal, the head of the adjusting bolt
incorporates a redesigned stamped seal protector and
rolled spring lips. The seal protector