Shimano early in their pursuit of better shifting (early 1980s) came up with (knowing Shimano's patent research dept, likely "borrowed" the idea) with what they called "W Cut" ring teeth. The tops of a pair of teeth were cut down in height, reasoning being that the chain wouldn't have to climb up as far to get over the teeth to move sideways to the inner ring. It worked fairly well and a trick/mod I have done to many non shift ramped/pinned rings to enhance their shifting. In my home made versions I increase the number of paired cut down teeth from two pairs about opposite each other to 5 pairs distributed evenly around the rings..

Having said the W Cut helps with shifting is all great it discounts the vastly larger component in the shifting system, the rider. Or more to the point the riders control box between the ears. I don't think I can count on the number of fellow club riders and so many customers who complain about front shifting, double and triples. Those who listen and take advice find that many of their issues go away after they learn and use best shifting techniques. Andy