A tankslapper on a loaded touring bike. Riding in Europe early in the trip on a Batavus I'd purchased in Amsterdam and loaded with my own handlebar bag, Pletscher rear rack and bags with a sleeping bag roll on the racktop. Long, fairly gentle downslope hill during which the front end began to wobble. My hands had never left the bars so I don't know how it began, but nothing I could do would stop it. Relax, nothing. Grip tighter and wrestle it, nothing. The wobble would not respond to braking and it only seemed to get worse after that, with the bars moving violently side to side and the front wheel almost hopping off the ground. Traffic was zooming by on my left and I had begun trying to find the softest-looking roadside spot for a bailout when the bike straightened out. I was never so glad to coast to a stop.