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1994 940 wagon with ABS brakes, Girling single piston front and ATE rear.
Yesterday I replaced the master cylinder with a new ATE unit then bled with a Motive pressure bleeder. The brake pedal still feels about as soft as it was with the old master cylinder. The front calipers slide smoothly on the guide pins. All front and rear brake pads are wearing evenly. I couldnt detect any expansion of the 4 rubber hoses when a helper pressed the pedal.
Pedal travel with engine off is 1.5 - 1.75 inches, this is within the 50mm limit in the FAQ. Starting the engine causes the pedal to drop another inch. With engine running and a really hard push, the total pedal travel is about 3 inches.
It just doesnt have the hard feel that it had when all brake pads were new. The front pads are currently 7mm thick, 3mm is the wear limit. Rear pads are 6mm thick, 2mm is the wear limit.
Perhaps I am expecting too much ? Brake fluid is slightly compressible (0.3% at 1200psi) so pedal travel should increase as the pads wear and fluid volume in the calipers increases. I found one internet source that calculated increased pedal travel of 0.5 inch due to fluid compressibility as the pads on a Triumph TR6 wore out and caliper fluid volume increased.
Has anyone experienced increased pedal travel and softness that went away when pads were replaced ?
Thanks,
Mike
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