I dissected a chain once and did a post on it, if you want to see what happens when o-rings go missing: http://www.advrider.com/forums/showthread.php?p=7124392#post7124392 The grease actually doesn't have anything to do with the rollers that contact the sprocket. There is an "outer pin" that the roller rides on and the grease is between that and the "inner" pin...or "axle" as you called it. Hope that makes sense. The link post might make it more clear, has pictures. Sorry for the hijack, just trying to help out the curious.