Bill is spot on..........I'm not saying that Vic is incorrect on the ESA as I can see his version is far superior to the original cam design, However, the issue with the Alton's and their supplied plastic gear is mostly a meshing problem.......And also the plastic gear has teeth that are wider than the stock steel item, so there is less side movement, that coupled to sloppy chainwheel bushes, and if the alton is not centered correctly will end up in rapid ware of the plastic item..........I've seen it a few times now.