Shimano's 105 tier has always been where trickle-down tech becomes accessible to riders who don't want to spend Dura-Ace money, and the ST-R7170 marks the first time Di2 electronic shifting shows up at this price point. The lever pairs with the included BR-R7170 flat mount hydraulic caliper as a matched hydraulic and shifting unit, so you're getting both halves of the system in one purchase rather than sourcing the caliper separately. If you're building a 12-speed R7100-series bike from the ground up or converting from an older mechanical 105 groupset, this is the shifter-and-brake combo that anchors the build.

The shift signal travels wirelessly from the lever to the rear derailleur, which eliminates the run of Di2 wire through the bar, stem, and headset that older 11-speed systems required. That single change simplifies internal routing on modern integrated cockpits and makes bar swaps or fit changes much less of a project. Each lever runs on two CR1632 coin cell batteries with a stated life of 3.5 to 4 years, so there's no charging routine to add to your list—when the batteries eventually die, you swap them like a watch battery and move on.

Ergonomically, the hood shape borrows directly from Dura-Ace development, with a raised peak and a longer hood body that gives your hand more to rest against during long days on the tops. Reach adjust is built in for smaller hands or riders who want the lever blade pulled closer to the bar, and the buttons can be reassigned through the E-TUBE PROJECT app if you want to change what the hood-top button controls or swap shift directions.... Read More