Just a thought and a 'what if' here... I used to have a '57 DeSoto Sportsman -- huge car -- and also wtih torsion bar suspension. IF the air in either of the front tires was lower than the other, (I don't know by how much), the whole car would shake if the brakes were used -- same symptoms you described.So my yorkie is running and driving once again, and I'm having some issues with the brakes. Being a younger guy (comparatively) with little to no 4 wheel drum brakes experience, I come seeking the wisdom of those here versed in drum brakes and full sized Chryslers. When I hit the brakes, whole car shudders, and you can feel it in the pedal. Every thing in the brakes is new, front and rear. Drums, shoes, hardware, wheel cylinders, hoses, adjusters and the master has been upgraded to a dual piston 1967 unit. The pedal is a little low so I'm gonna try and adjust the brakes now that I've put a few miles on it (I'd say ten miles.) Is this just an adjustment issue, or should I look somewhere else? Thanks in advance!