I've just started driving my model A with hairpin suspension and single leaf spring. It's all new parts and assembled well, but when I hit some bumpy roads at speeds, the front end oscillates badly, practically vibrating the steering wheel out of your hand.
It only happens on bumpy roads. Any other time, even at 90 mph, it's fine. Is this just an inherant trait of a 1920's designed suspension, or can I do something about it?