1 - IT'S MOSTLY A FACELIFT

Underneath the new all-black styling of the 9100-series Di2, many of the fundamentals (cassette, chainring, derailleur motors) are the same as the previous generation 9000-series Di2. That’s probably why shifting performance is indistinguishable from before - not a knock, since the 9000 series was already the smoothest shifting and most polished drivetrain on the market, despite recent improvements by SRAM and Campagnolo.


2 -  . . .EXCEPT FOR THE HYDRAULIC DISC HOODS AND LEVERS. THEY’RE DIFFERENT - AND THEY ROCK

The stars of the group are the revised dual-control levers for electronic shifting and hydraulic disc braking. The hoods are comfortable and substantial enough for a secure grip when you’re out of the saddle. The length, width, and contours of the levers are more pleasing than Shimano’s first dual-control lever for Di2 and disc brakes, the blocky and extra long RS785.


3 - THERE’S A POWER METER

The new integrated power meter crank (an additional cost) features independent left and right power measurement in the crankarms, with a rechargeable battery in the axle. Claimed accuracy is +/- 2 percent. It broadcasts on ANT+ and uses Bluetooth LE so you can adjust settings and push firmware updates through your smartphone.


4 - THE BUTTONS FEEL BETTER, AND IT’S HARDER TO MIS-SHIFT

The new Di2 shift buttons have a more definitive click (in feel and sound). They rattle less, and we experienced fewer accidental gear changes (particularly while wearing long-finger gloves). The shift button closest to the handlebar is about 1cm longer now and easier to reach from the drops.