Wheelbase length could be the problem, or weight distribution. Weight on the saddle as far back as possible and I can ride no hands-just. On the Tandem my pilot scared me the other night as he asked me to sit very still in the saddle for a while. 30 seconds later he told me that we had just gone 100yards no handed. He just wanted to see if it was possible. The reason he asked me to sit as still as possible is that the one on the back of a tandem really does affect the stability of these beasties. 100yards no handed and I should have felt chuffed, but not at 30mph on a road that was not exactly free from traffic.