Tool: Park Tool DAG-2 Derailleur Hanger Alignment Gauge

Job:  To align your derailleur hanger.

Thumps Up:  The DAG-2 is an updated version of the classic DAG-1 alignment gauge.  The DAG-2 is just as simple and effective to use as the original, but it’s been designed to work on a wider variety of frames.  Many full-suspension frames no longer use the traditional 135mm spacing for the rear wheel, and as a result the DAG-1 tool would bottom out on the frame before it could be fully tightened.  The DAG-2 was designed with such bikes in mind, and thus can be used on virtually any frame.

Thumbs Down:  Since this tool is so long, it is possible to use that leverage to accidentally break your hanger right off the bike.  Take care not to apply too much pressure when straightening it.  If your hanger feels particularly rigid, you’re better off just installing a new one, because some hangers are resistant to being realigned and will crack or break completely.

Tool Tip:  Make sure that the bolts attaching your hanger to the frame are tight before you attempt to straighten the hanger.  Also, since you will be using your rear wheel as the point of reference when aligning the hanger, it’s best to check the tool against a consistent spot on the rim.  As you check the 3, 6, 9, and 12 o’clock positions on the wheel, line the tool up with the valve stem and rotate the wheel with the tool to get the most accurate result.

Last Word:  While the DAG-2 is an indispensable tool for any bike shop, it’s also valuable to a home mechanic.  Considering what a bike shop would charge to align your hanger, use this tool three times and it will have paid for itself.

Info:  Retails for $60

Katie Arhart-Rose – Boulder, CO