Originally Posted by
MikeyMK
It matters not whether the difference is significant, it is a matter of direction. It's often easier to work these things out as being case A or B by comparing an amplified version - In case A you have a 50kg rider and 40kg bike. In case B you have an 85kg rider and a 5kg bike. You then decide who has the easiest ride. If you arrive at case B in the extreme, then chances are it's going to be case B in the lesser extreme scenario. Of course, it may not always be that simple..
That's not helpful at all. Assuming that the riders are approximately the same size (or this is now an aero question instead of a weight one), you now have a rider who's probably well below average in strength operating a bike made out of lead. At least when the riders were closer to each other in weight and size, there was some question as to differences in fitness levels. By going to extremes, I either have to assume that one of the riders is very heavy for his size or very light, both of which possibilities will affect the rider's ability. If anything, you've just demonstrated that we don't have enough information to answer the question--we need to know what kind of extra weight the heavier rider is carrying because leg muscle might improve performance.