Bent derailleur hangers cause shifting problems that no amount of cable tension adjustment will fix. The rear derailleur needs to hang perfectly parallel to the wheel—even a couple millimeters of misalignment at the hanger translates to centimeters of error at the jockey wheel, which means missed shifts, chain rub, and that maddening hesitation between gears. Park Tool's DAG-2.2 lets you measure that alignment precisely and bend the hanger back into spec without removing anything from the bike.

The gauge threads directly into the derailleur hanger where your rear derailleur normally mounts. A long indicator arm extends outward and rotates around the axle, letting you check the hanger's position relative to the rim at multiple points. You're looking for the same gap measurement at twelve o'clock, three o'clock, six o'clock, and nine o'clock positions. Any variation tells you the hanger is bent, and the direction of the variation tells you which way to correct it. The tool itself becomes the bending lever—controlled pressure at the handle straightens the hanger incrementally until your measurements match all the way around.

The DAG-2.2 works on virtually any rear derailleur hanger configuration, including direct-mount hangers and those integrated into the frame dropout. An adjustable indicator with a threaded shaft lets you dial in precise measurements regardless of wheel size or rim width. The gauge arm telescopes to accommodate different wheel diameters and extends far enough to clear disc brake rotors without interference.... Read More