..if the brakes and lines are new or in good repair means there is nothing wrong...changing to the correct master cylinder shouldn't kill him.He probably shouldn't try bedding the pads on a 12 lane freeway at rush hour though.
Good point.
Your right changing to a correct master cylinder shouldent kill him. However your initial post did not recommend that, only to bed them in at higher speeds which he currently cant do since the car wont stop very well the way it currently is.
You are correct with the basic fluid dynamics. If the piston in the master it too big, you will get a hard pedal and decreased grip from the calipers. Too small of a master cylinder bore will also give you decreased grip from the calipers with a soft pedal. The master needs to be sized just right for the amount of pedal force required and caliper grip required for the particular application.
