Hard pedal

AJ, overall good work. I came up with 2cc's front and 3 cc's rear with a given set of what I think are good assumptions for the fluid into discs and cylinders; I used more seal retraction with a single piston system, 1" wheel cylinders and a tad less wheel cylinder travel. So the same ball park. But, change the assumptions a modest amount, and your or my results for the capacity needed can reverse, with discs needing more than drums. All the numbers we have used are grabbed from the air and not measured. It is too much of a stretch to make any hard conclusions for all situations from such numbers.

If I have it right, the MC piston for the front brakes has to push the distance that pushes the fluid needed for both front and rears. If I read your work right, you used only the front caliper volume to work out the MC stroke. Please check me out, but I think that yields a 4:1 error in the fluid movement portion of your MC stroke computation if one uses your 3x larger wheel cylinder fluid volumes. And it may have to push even more stroke to get the comp port on the rear chamber covered too if it closes later than the front port to possibly add more MC stroke. (I have no clue about the sequence of comp port closures however.)

And from direct experience with going from rubber lines to stainless braided lines, I can honestly say that the amount of fluid needed due to line expansion can be quite large. Just from the sensed pedal movement changes in those cases, it can be as large than the caliper and wheel cylinder fluid capacity for moderate to hard braking (like racing).

BTW, I don't think anyone one said that a drum/drum MC wouldn't work a disc/drum setup. Re-check the postings above. (And I did not go back and change a word.) I did say that there was a case for disc/disc where a larger MC bore fixed the problems and provided the link to that. The point was to try to give the OP a head's up on this potential issue as he looks at rear discs.

The older , short height, small reservoir MC's for drum/drum don't have the capacity to keep filling the space behind the caliper pistons as the pads wear, but as you say, that only has to do with long term wear, not for an individual braking stroke.

And let me bold a few words too.... a few words