I did the wrong math! I was looking at the 4piston setup of the Code(?). 16mm & 15mm
Etap (classic) / monoblock = 2x 21mm pistons w/ 2.4mm pads-in spacer (~1.2mm travel/side) https://www.sram.com/globalassets/docum ... manual.pdf & SRAM Spare parts catalog
AXS / Level Ultimate /Split block = 2x 21mm pistons w/ 2.8mm pads-in spacer (~1.4mm travel/side) https://www.sram.com/globalassets/docum ... manual.pdf & SRAM Spare parts catalog
HRD = 2 x 18mm x ?? travel relative (Different spacer/bleedblock design).
So.... caliper piston area per side.... but the motion ratio (leverage of the master cylinder) is important too..assuming the rotor/pad spacing is the same for all of them.
AXS = 346mm2 * travel factor (relative to 1.2mm) 1 = 346
ETAP = 346 * (1.4/1.2) = 403 (16% more fluid pumped than AXS)
HRD = 254mm * .77 (1.85mm total??? 0000000005275_mtb_disc_brake_hose_shortening_and_bleed_eeu_rev_d.pdf prior gen level brakes) = 196 (seems pretty low)