In one of the many topics that there are currently in the forums about disc brakes on road bikes, I had a small discussion about the effects of the braking system in rear end's deformation. I was pretty sure that rim brakes generate less vertical deflection of the wheel axle during braking so I decided to write the equilibrium equations to confirm my thoughts.
To simplificate things, I have considered the rear end to be plane and formed by two identical tubes. I have also applied linearity (small strain) in the system to avoid having also to consider inertial and slipping forces due to deceleration. If something isn't clear, don't hesitate to ask
PD If the disc brake force isn't parallel to the seatstays, the M moment is even smaller, so the vertical deflection would be bigger.