Originally Posted by
Duke of Kent
Half wheeling only occurs when you're at the front of the group, pulling. It doesn't have anything to do with speed. In my neck of the woods, it generally happens with a crosswind, when a stronger rider is on the windward side, and the weaker rider is forced to hide in his draft by riding next to him, but slightly behind him, usually 6-12". Half a wheel behind the other guy pulling. Hence "half wheeling".
That would be an echelon (a good thing to know). Half wheeling is when a group is riding in two lines and the lead rider in one always moves to be a half-wheel ahead of the other. The second rider, trying to keep the lines even speeds up to match the other who again moves ahead by another half wheel. The pace keeps going up until the pacesline is totally disrupted.