with or without a rider, a bicycle does need a well-balanced and maintained steering system to remain upright.
This comprises the handle bars, the handlebar stem, the front forks and the head-set.
the headset is an unglamorous but fundamental component of the bicycle. it’s also a part that takes terrific beating from the road. The ball bearings contained within the lower cup of a headset are loaded differently from those in all other rotating parts of the bicycle. They are loaded axially, and they hardly rotate – an undesirable situation as impacts from the road are transferred to stationary ball bearings. This is called ‘thrust stress’ and it can cause pitting or brinelling of the bearings. The problem is exacerbated riding off-road, or on a loaded touring bicycle.