Building a gravel bike around Shimano's GRX Di2 2x 11-speed platform means committing to the mechanical-hydraulic hybrid the industry landed on before wireless took over — and for a lot of riders, that's still the right call. This kit bundles the ST-RX815 shift/brake levers with BR-RX810 flat-mount hydraulic calipers, the FC-RX810-2 crankset in a 48-31T configuration, the FD-RX815 front derailleur, the RD-RX815 rear derailleur set up for cassettes up to 34T, and the matching cassette. Wires, battery, and junction boxes are sold separately since bike-specific routing dictates what lengths you actually need.

The gearing math is where GRX earns its keep on mixed terrain. The 48-31T crankset paired with an 11-34T cassette gives you a low gear roughly equivalent to a compact road setup with a wide cassette, but with tighter steps between the two chainrings than a 50-34 would deliver. That closer front spacing means fewer big drops in cadence when you shift between rings mid-climb, which matters more on gravel than it does on pavement because you're already fighting rolling resistance and terrain variability. Synchronized shifting through the Di2 system will handle the front shifts automatically if you want to run the drivetrain in Semi-Sync or Full-Sync mode.

The ergonomics carry over the design work that separates GRX from repurposed Ultegra parts. The hood shape sits taller than a road hood with a raised head and a recessed finger notch, both of which keep your hand from sliding forward when the front wheel drops into a rut. Anti-slip texture on the hood covers and brake lever face adds grip when you're gloved up or riding in the wet. The brake lever pivot sits 18mm higher than the standard road position, which shifts the mechanical advantage to give you more stopping power with less effort from the hoods — where you'll spend most of your gravel miles.... Read More