Just out of curiosity what are the main factors that determine whether a long cage or short cage derailleur is fitted. The reason for the question is that both my bikes have 14/28 rear clusters but the one with the short cage Huret has 54/42 chainrings and the one with the long cage Suntour has 50/36 chainrings. It almost feels that they should be the other way round. Hope this is not a silly question!