Many Shimano mountain bike rear derailleurs offer a clutch mechanism, which when engaged holds the derailleur cage in place, preventing cage movement and chain slap. Many mountain bikers simply leave the clutch ON, or locked all the time. What few riders know is that the actual tension held by the clutch is adjustable, and when the clutch is on, the spring that creates friction within the clutch unit is constantly under load, and it loses it stiffness over time. The bolt that controls the spring tension interface is quite narrow, requiring a small thin tool for access ad use. The Park DW-2 Derailleur Clutch Adjustment Wrench is a quite thin, compact steel tool with two openings: 5.5 and 3mm to work with all of the Shimano adjustable clutch bolts.

You can set, or adjust your clutch friction via a screw that sits under the clutch cover of the derailleur. There is a steel spring that can fatigue over time and require additional tension. Or perhaps you feel there is too much tension or drag on your drivetrain, and you want to back some of that off. The DW-2 fits the two bolt sizes Shimano has used on Shadow Plus (Plus means clutch option) rear derailleurs. Shimano recommends 1/8th turns of the tension screw- very incremental. Please follow all Shimano instructions for servicing or adjusting this assembly. One key tip: the clutch cover is designed to keep out water, dirt etc. As such it has a thin gasket that mates with the clutch housing. Make sure you identify and retain the gasket when you remove the cover, and make sure it is reinstalled properly before you re-attach the cover.

If you have Shimano XT, SLX, Deore, Saint and Zee rear Shadow Plus (+) derailleurs and all previous Shadow Plus models, you will be able to adjust the clutch spring tension. Some XTR Shadow Plus units came with an integrated (but removable) tool for this purpose. Please see Shimano's tech bulletins for working on those models. There are few tools as specific, and absolutely crucial as the DW-2, so you can thank Park for this perfect example of why Park Tool exists.