SAFARI

14 BRAKES Fig. 4 - Twin pot caliper cross sectional view Clearance Correction When fluid pressure is applied on the piston, both pistons move forward. The rubber seals, which exert considerable pressure against the pistons, are fixed into grooves in the caliper, hence the shape of the rubber seals are distorted at the I.D. as shown in Fig. 4. When pressure is withdrawn from the brake pedal and fluid pressure is released from the piston, a restoring force is generated by the seals and they push the pistons back to its original position. As the pads wear the clearance between the disc and the pads becomes larger, hence the pistons have to move a larger distance. The seal then could change in shape further but, since the seals are fixed into the grooves in the cylinder, the distortion is limited to the same amount as previously described. The piston moves further to cover the distance of clearance relative to the seal in the case. The pistons return by the same distance and the rubber seal recover their shape as described above and thus the clearance between the disc and pads are maintained by adjustment automatically.The caliper brake needs no adjustment. CYLINDER PISTON SEAT (RUBBER SEAL) PISTON HYDRAULIC PRESSURE ‘ON’ CYLINDER PISTON SEAT (RUBBER SEAL) PISTON HYDRAULIC PRESSURE ‘OFF’ CARRIER CLAIPER HOUSING SEALING RING PISTON SLIDING PIN PAD SLIDING PIN BOOT SLIDING PIN BOLT Caliper Operation When the brake pedal is pressed, the hydraulic pressure fromMaster Cylinder pushes the pistons and with it the in-board pad on to the disc. The caliper body reacts and slides on the sliding pins to bring the out-board pad into contact with the disc.The clamping forces on both slides of the disc thus become equal. When the hydraulic pressure is released the sealing ring fitted in the grooves of the cylinder retracts the pistons by a small amount which allows the moving parts to relax sufficiently for the disc pads to retract and remain in close proximity to disc, ready for the next brake application.