travel of master cylinder piston on a 1949 P3/75.

Can any one guide me as to how much travel the piston should have in the cylinder after the little bit of free travel has expired and the pressure is applied from the brake pedal to the piston. any advice would be greatly appreciated. best regards Derrick.Smith.


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All I can find in what remains of my little blue book on the 48-56 cars is 1/4" free play at the pedal. IIRC the master is an unusual shape, different diameters and a large nut on the end to aid dismantling and cleaning. Two rubber cups inside, one on the piston, one stationary that the piston runs through? I had some trouble with mine with getting the linkage to the rear mechanicals balanced and working. I suggest you might need some soft woven type linings at the rear.
What the issue you are looking at?


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I don't really understand the question, once the clearance between the push rod and the piston is taken up , further pressure on the brake pedal pushes the piston until the brakes are applied , which will vary depending on whether the brakes need adjusting. The P3 has a hydro-mechanical system, fronts hydraulic and the rears mechanical and used a Girling Compression Barrel ( CB) cylinder . Picture of a Land Rover one , but the principals of operation are the same .



Active Member
I suspect Derrick is having trouble with front/rear linkage. IIRC the rear linkage will absorb motion until the rear linings are all contact with then drums before it will move the hydraulic piston much - do you have anything on the set up of the linkage?
Thank you all for your mechanical wizardry. i have taken the master cylinder back out of the vehicle for a closer inspection and what did i find, after spending $300 and having it repaired at a specialist brake and clutch business. they had omitted to replace the retaining washer for the piston and cir-clip fixing washer. no wonder when struggling with the push rod for the piston it almost came out, hence my question about the free travel. so off i go back to the repairer where i explained to them what i thought had happened, no that could not be the case was the reply. after they agreed and replaced the missing parts an interesting conversation took place when they tried to charge me again. best regards Derrick.Smith. P.S wishing you all a holy happy and safe christmas.