Internal spoke nipples hide inside the rim where a standard spoke wrench can't reach them. You'll find this design on deep-section carbon wheels, some aero aluminum rims, and various high-end wheelsets where external nipples would disrupt the rim profile or require drilling access holes. When these wheels need truing—and they all eventually do—you need a wrench that works from the hub side, reaching down through the spoke hole to engage the nipple.

Park Tool's SW-15 handles this job with three common internal nipple sizes built into a single Y-shaped tool. The 5.0mm hex fits Square and Hexlobe nipples from DT Swiss, the 5.5mm hex covers Sapim's Polyax internal nipples, and the 6.0mm hex works with Shimano's internal nipple wheels. That covers the majority of internal nipple wheelsets you'll encounter in the shop or at home. The tool drops straight down through the spoke hole from the hub side, engaging the nipple so you can make tension adjustments without removing the tire or rim tape.

The Y-handle design gives you enough leverage for stubborn nipples without going overboard. Internal nipples can seize up from corrosion or thread-locking compound, and having a proper grip makes the difference between a successful true and a stripped nipple. The compact size fits in a tool roll if you're dealing with wheel issues at events or on long tours, though most internal nipple truing happens in a stand where you can work methodically.... Read More