Originally Posted by
MyRedTrek
They're basically a no-name clone of other shifters with the same basic construction - two main pieces and a spring inside the fixed part that rides over a series of humps molded into the outer piece that you twist.
I suspect there's a delicate balance with that spring-and-hump design of providing enough friction or retention to prevent the derailer from pulling the cable back through the clicks, but not so much friction or retention that the shifter is easy to operate. I bet that range is somewhat narrow, and trying to modify that may net poor results.