Shimano Dura-Ace Di2 ST-9071 DH Bar Shifters

Shimano makes two versions of Di2 electronic shifters to place at the end of aero bar extensions. This SW-9071 DH Bar Shifter is the version that has one button on each shifter. One button per shifter means that one side handles the up shifts. And one side handles the down shifts. 

 

The idea behind doing this is simple. When time-trialing, you're rarely shifting out of the big ring. If you've got a course where you shift into the big ring before the start and leave it there until after the finish, it's nice to have the precision of letting one thumb make pedaling easier and one thumb to make it harder.

 

The ST-9071 Bar shifters come pre-programmed. One goes up and the other goes down. You can choose which one goes on the left and which one goes on the right. If you don't like how you have it set up, you can switch the buttons by moving the pods from one side to the other. Or, you can re-program them with the SM-PCE1 programming/diagnostic tool. With that, you can also program how many shifts each button can make per time you hold down the button. One, shift, two shifts, three shifts, the big slam, it's all possible.

 

Each pod comes with the necessary mounting hardware and 300mm of wire attached. You'll probably want a five-port SM-EW90 Junction Box under the stem to join these with. You'll want the five so you can still have dual-control brake levers and these bar-end shifters.

 

If you're looking for super-simple up-and-down convenience on your aero bars, the Shimano Dura Ace Di2 SW-9071 bar end shifters are the answer.