Originally Posted by strongbad
If the scale(s) are accurate, and the bike is level, the weight measured with a scale under each wheel then added, or a scale under one wheel at a time then added, is accurate. The key thing is that the bike must be level.
Experimental aircraft builders get weight and balance info this way sometimes.
That's what gave me the idea, because I've been involved with weighing a few experimentals, but we were using three scales simultaneously and they were accurate scales too.