Building a 105 Di2 bike from scratch means sourcing a lot of individual components, and getting them all in one order simplifies the process. This kit bundles the core Di2-specific pieces you need for a complete R7170 build: the shift/brake levers with hydraulic calipers, both derailleurs, the seatpost battery, charging cable, chain, and cassette. What it doesn't include are the components where frame-specific or rider-specific choices matter—you'll need to source a crankset, bottom bracket, disc rotors, and the EW-SD300 wires that connect the derailleurs to the battery separately.

The R7100-series 105 exists only as Di2. Shimano didn't release a mechanical version of 12-speed 105, so if you want 12-speed at this tier, electronic shifting is the path. The system uses what Shimano calls a semi-wireless architecture: the ST-R7170 shift levers communicate wirelessly with the rear derailleur using a secure signal powered by two CR1632 coin cell batteries in each lever. Those batteries last 3.5 to 4 years before needing replacement. The derailleurs themselves still connect via SD300 e-tube wires to the BT-DN300 battery that sits inside your seatpost. This approach keeps the cockpit clean—no wires running through the handlebars or stem—while maintaining the reliable power delivery that servo motors need for consistent shifting.

The rear derailleur serves as the system's hub, housing the charging port, LED indicators, function button, and D-FLY connectivity for pairing with cycling computers. You charge the system by attaching the included EW-EC300 magnetic cable to the rear derailleur. Shimano rates the shifting at 58% faster on the rear and 45% faster on the front compared to the previous wired Di2 generation. The RD-R7150 handles both the 11-34T cassette included in this kit and the 11-36T HG710 cassette if you want additional climbing range.... Read More