Originally Posted by
billridesbikes
The second issue is called “shimmy”.... It could also be some weight hanging on the handle bars like a water bottle or handle bar bag where the contents are shifting back and forth.
Weight on the handlebar could be a cause of this problem, but adding weight to the handlebar or fork could also be a solution - more weight will tend to decrease the resonant frequency and so shimmy will not occur at the speed it was happening at. It might become more likely at lower speeds, but 'death shimmy' at 18km/h is unlikely to be even noticed - most would just accelerate through the speed range where shimmy occurs and never notice.