Pro tip: a crusty old mechanic in Denver said to file dropouts before aligning them, and I ignored him for 3 years
Back when I was still pretty green around 2019, this older guy named Walt who ran a tiny co-op in Denver kept telling me the same thing every time a bent hanger or tweaked dropout came through: file it flat first, then align it. I nodded along and kept right on using my DAG, because bending a hanger back into shape had always worked fine for me on my own bikes and a handful of customer ones. Fast forward to last month and a customer brings in a 2016 Salsa with a rear wheel that would not stay centered no matter what. I spent about 90 minutes fighting it, eyeballing the DAG, tweaking, rechecking, still off. Finally pulled the wheel and ran my thumb across the dropout face, and it felt like a washboard. The hanger had been bent and straightened so many times that the face itself was chewed up, so the derailleur never sat square even when the gauge read straight. Two minutes with a flat file and a drop of oil, then a light pass on the alignment gauge, and it lined up dead straight first try. I felt like an idiot. Walt was right and I owe that man an apology. Any of you file the faces on a beat dropout before you even touch the gauge, or am I late to a party everyone else already knew about?