TRIUMPH 1300 BRAKE ADJUSTMENT
Q I have a 1966 Triumph 1300 and despite regular adjustment of the rear brakes, I continue to find that shortly after making the adjustment, I again have a long travel on the brake pedal. Further adjustment cures this for a short time, but not for long. When the adjustment is made, this does not seem to need more than one notch on the adjuster. The brake linings are in good condition and not low, the front brake pads are good and I have checked for any signs of fluid loss from the master cylinder and at the wheels, but the problem does not appear to be the hydraulics. The handbrake works well when the adjustment has been made and the cables are free.
A As you have mentioned the brake linings are good, I am presuming that you have removed the rear brake drums to check these. From the details I have on your Triumph, it has the sliding single piston type of wheel cylinder and it may be the case that this is not sliding easily in the backplate. Freeing this off may help, because if during adjustment this is not sliding freely, then that would impair the operation of the brakes and your ability to perform a correct adjustment.
Another check to make is to ensure that the adjuster is free to operate, and that both of the small slides within the adjuster move freely. Another tip on the adjuster is that it bolts to the backplate and can move. To ensure it sits in the optimum position, loosen off the securing nuts on the adjuster and get an assistant to push the brake pedal firmly down. Then, when the brakes are firmly applied, tighten the adjuster securing nuts; this will ensure that you have the unit mounted in the most central position.