Originally Posted by
Kimmo
But it does matter that teeth are profiled. I can see what you're saying possibly applying to Uniglide or earlier, but on anything not ancient climbing the teeth is pretty easy.
The only way you're going to feel much resistance to that these days is shifting to a bigger cog with a clutch derailer.
"Feel"? The amount of friction you overcome yanking on the shift lever is much, much greater than this gravitation thing you've fastened upon. The friction just in the parallelogram pivots are more than the slope weight of the lower derailleur.
Anyway, the OP's problem is not that he's riding the bike upright, but that something is either out of adjust, at the wrong angle or has too much friction resisting the spring. The first thing to check would be up shifting while pedaling by hand very slowly. If that doesn't work, use the rear cable housing stop slot to disconnect the derailleur cable and see if the derailleur will drop into high when there is no cable drag at all.