USER MANUAL Tractor semitrailers PTL
48
7.2.
Brakes
7.2.1.
Servicing of the pneumatic brake system
During the use of the tractor semi-trailer, it is necessary to check the tightness of the brake system and
condition of its elements, to periodically remove condensate from the reservoir.
The tightness of the system shall be checked under nominal air pressure of 800 kPa. Characteristic
hissing or occurrence of bubbles after applying soapy water to the suspicious place is considered as an
indication of a leak. If the leak is caused by damaged spacers or other parts of the system, they must be
replaced with new ones.
Condensate shall be removed from the reservoir by pressing the drainage valve. Once a year, before the
winter season, the drainage valve must be screwed out and cleaned.
7.2.2.
Adjustment of the elements of the pneumatic brake system
During the use of the tractor semi-trailer, it is necessary to check the efficiency of the brakes and
periodically lubricate the marked points.
The adjustment of the brakes shall be performed when:
the brake blocks are worn-out. The space between the brake blocks and drum increases, causing
the impairment of braking efficiency;
the wheels are braked not simultaneously and not uniformly.
When the brakes are adjusted correctly, the braking force (the sum of braking forces acting upon the
wheels being braked) should account for min 27 % of the permissible total mass of the semi-trailer when
braking with the working brake, and the braking force (the sum of braking forces acting upon the wheels being
braked) should account for min 16 % of the permissible total mass of the semi-trailer when braking with the
hand-brake. Both wheels of one axle should brake uniformly. The difference of the braking forces between the
left and right sides of the semi-trailer should not exceed 30 %.
The adjustment of the brakes shall be performed only after the adjustment of the bearings of the wheel
hub, by changing the brake shaft's brake lever torque or angle of the brake lever in respect of the shaft. For
this purpose, it is necessary:
place protection wedges (blocks) under the wheel opposite to the one being adjusted;
insert a jack under the axle, at the marked place, and lift the wheel;
while rotating the wheel, also turn the adjustment bolt 4 (Picture. 22) until the braking blocks
touch the drum.
The moving distance (motion) of pneumatic brake chamber connector should be 60 - 65 mm, and the
difference between the force of the chamber connectors of all the wheel chambers should be not more than
5 mm.
