The new Pinion Smart Shift gearbox is designed to seamlessly integrate with TRP Hywire drop bar shifters. The shifts are electronic and take just 0.2 seconds to complete.
But what happens if you ride a gravel bike, and prefer the ergonomics, lever feel, reliability and brake performance of Shimano GRX Di2? Can you wire a Pinion Smart Shift gearbox to Shimano GRX Di2 levers?
One CYCLINGABOUT reader was dissatisfied with his TRP Hywire levers. Patrick found that the brake master cylinder leaked droplets of hydraulic fluid that accumulated over time and ended up on his hands and handlebar.
Patrick decided to go on a journey to see if Shimano GRX Di2 shift levers would work instead. This was never going to be a straightforward task as Shimano uses proprietary plugs for their Di2 system. In other words, you can’t just connect the Shimano wires to the interface of a Pinion Smart Shift gearbox.
But Patrick still found a way to combine Shimano GRX Di2 levers with a Pinion Smart Shift gearbox! You can read his step-by-step tutorial HERE.
How To Wire Shimano GRX Di2 Levers To A Pinion Smart Shift Gearbox
Inside Shimano GRX RX815 levers are two shift buttons that connect to a small, round “function box”. This function box contains the interface electronics for the Di2 plug. For Patrick to make this hack work, the Pinion Smart Shift wires would need to be soldered directly to the wires inside this function box.
Patrick first removed the rubber cover of his right-hand GRX Di2 lever and untightened a small screw to gain access to the function box.
Next, he had to get inside the function box. A cap had been glued over the body of the box, so Patrick carefully cut through the glue until he could insert a spudger and pry off the cap. And there it was – the circuit board with the interface electronics.
Patrick pried up the circuit board to reveal three wires connected to the shift buttons. The wires were de-soldered and the Di2 cable was pulled from its hole. He then used a multimeter to confirm the shift buttons were wired up to function as expected. Yellow was “shift up”, purple was “shift down” and grey was a common wire that completes the electrical circuit.
To conveniently connect and disconnect the lever, Patrick purchased two 3-pin Higo Mini-X connectors/sockets. He soldered one of the cables to the function box and the other to the wire that originally came with the TRP levers.
The hardest bit was soldering the new wires to the existing wires inside the function box. The box is incredibly small and the cable lengths inside the box were very short. Patrick also had to remember to put heat shrink on the wires before soldering.
Once everything was soldered together, Patrick decided to fill the whole box with hot glue to seal it from humidity and protect the wiring from vibration. There was no need to re-fit the original cap as the box was now fully potted with glue.
And just like that, Patrick likely had the world’s first Pinion-compatible Di2 shifter!
Connecting The Levers and Gearbox
The last thing to solder was the other Higo connector to the Pinion Smart Shift cabling connecting to the gearbox. Patrick then added some heat shrink over the wires and hid them all in his downtube.
Currently, the shift buttons on the Shimano GRX RX815 right side lever are working fine and reliably. If Patrick wanted, he could connect the left lever in a similar way to be able to shift with both hands.
You can see more pictures and information about the Shimano GRX Di2 hack HERE.
