Andrew R Stewart
Join Date: Feb 2012
Location: Rochester, NY
Bikes: Stewart S&S coupled sport tourer, Stewart Sunday light, Stewart Commuting, Stewart Touring, Co Motion Tandem, Stewart 3-Spd, Stewart Track, Fuji Finest, Raleigh Pro, Trek Cycle Cross, Mongoose tomac ATB, GT Bravado ATB, JCP Folder
A number of years ago at one of the industry shows (East Coast, Philly I think) I asked the SRAM (actually IIRC they were just Sachs then) guys much of this same question. Their answer was that the manufacturing tolerances were loose enough (with all brands they tested, not just SRAM) so that you'd get a range of "measurements" on even new chains along the chain's length. I know I've gauged (and this is what most wear indicators do) new chains and gotten readouts suggesting much wear.
Still we use chain wear gauges at work daily. To some degree I feel there is an aspect of judgment at play. This is why i prefer to use the same gauge each time I check a chain. Andy.