Shimano’s radical new GRX Di2 system digitises your bike

The Japanese manufacturer is back with a new and improved version of its electronic shifting tech – the ideal setup if you want to drag your analogue ride into the digital age


3 days ago

Powered shifting – changing gear with an electrical signal not a traditional gear cable – isn’t strictly new, Suntour released its Browning Electronic AccuShift Transmission (snappily known as BEAST) back in 1990. Mavic then released it’s Zap system in 1992. Dogged by reliability issues on the professional racing circuit the before-it’s-time system faded out just before the company had another try with it’s similarly doomed Mektronic system.

Fast forward to 2009, and Shimano launched the first successful electronic groupset (a set of gear and brakes) called Di2 (Digital Integrated Intelligence). A perfect storm of technological advancement, committed investment and pro-team development meant electronic shifting was now here to stay.

Now Shimano’s back with an upgrade to this in the form of its GRX Di2 system – priced at a cool £1,750.85. With an option of running a single front chainring, adding a ‘clutch’ derailleur (tensioned so you shouldn’t ever drop your chain) and mix-and-match compatibility with other Di2 components, GRX is now the most versatile group-set in electronic shifting.

All systems of this ilk use a PLC (power line communication) to send signals and draw power through a series of wires that connect switches in the brake levers with an internally mounted battery (in the bike’s seatpost) and the only moving parts, the derailleurs (the actual gear shifters).

So why switch to electronic?

1. Accuracy. Traditional bike gearing relies on metal cables, so it’s a system with inherent friction. As the cable passes through the ‘gear outer’ and round corners (especially with modern, convoluted internal cable routing) friction adds drag and loss in accuracy. Factor in cables getting stretched and dirty over time and your once slick gears aren’t so slick anymore. Electronic gears never lose alignment or gain resistance in the shift. It’s just an electric signal after all.

2. Programmable shifting. Using a smartphone or desktop app such as Shimano’s E-Tube riders can remotely customise how the derailleurs behave and what each of the shifting buttons do. Want to shift the rear derailleur with your left hand instead of right? You got it. If you’re running a single front chain-ring and want both buttons on the left to shift up the cassette and both on the right to shift down? No problem. Hell, if you want to do something really out of the box like upshift the front mech and rear mech on one side and down shift on the other (no matter how confusing that may end up) you can do that, too. The entire system is fully customisable.

3. Multiple gear shifters. With a regular road bike set up, riders have gear shifters on the left and right brake lever only – obviously that’s where the cables run to. Electronic gearing gives you the opportunity to add additional gear-shifting buttons in different locations. This means riders can stash shifters under their handlebar tape or on the end of extended triathlon bars – anywhere that you can run a wire to, you can add a shifter. This is perfect for time-trial bikes and triathlon set-ups as well as unconventional frame shapes and bikes for people with disabilities.

4. Connectivity with other bike tech. This is where an electronic system gets clever. Using the E-Tube app, riders can reassign additional hidden buttons (on the inside of the brake levers) to interact with other digital devices. An inline Bluetooth unit enables hands-free swiping through your Garmin or Wahoo ELEMNT GPS device (to view your route profile, distance, average speed etc), perfect for those out-of-the-saddle efforts, or for off-road riding when the terrain is just too rough to move your hands from the brakes. You can also configure the Garmin to display information on the system itself – for detail on battery percentage and gear ratio... Data geeks rejoice, it’ll also tell you how many times you’ve shifted gear at the end of each ride, too.

But there's a downside, right?

There are a couple. The biggie? Running out of battery. All Di2 systems run on a single battery and each charge (from flat to full in 90 mins) lasts up to 2,000km, according to Shimano (amateur riders shouldn’t need to charge the battery more that four times a year). Obviously this depends on how much you change gear. You can check the charge level via the junction box usually mounted under your stem or via that E-Tube app. If, for some reason, the battery runs flat then you’re simply left without shifting. You’ll then need to select the gear in which you want to ride home ‘singlespeed’. The second downside? Price. Buying a system like Ultegra Di2 could set you back around £1,000, the top end Dura Ace? Nearer £2,000. SRAM’s Bluetooth Etap gear-only system comes in at a similar price. Buying a new bike equipped with Di2 is better value and will generally add from 10 to 25 per cent to the price.

OK, how does it actually ride?

Initial impressions are mightily impressive. From the very first shift the experience is completely different from regular cabled gearing – remember, you’re ditching analogue for the precision of digital. Your physical interaction with the shift levers is a digital button tap, not a physical pull of a cable. There’s no need to slightly ‘overshift’ up to move the derailleur up, or endure a tiny lag in a downshift as the spring of the rear derailleur drops the gear down (the electronic derailleur relies on the motor alone to move in either direction). Shifting on and off-road is spotless. Shifting down the ‘block’ is swift with virtually no lag. Shifting up is almost imperceptible – save for a tiny ‘ziiit’ from the electronic derailleur. It just works.

Connecting the app via bluetooth is straightforward, too. Shimano aren’t going to be winning any awards for the E-Tube app design, but pairing with the bike and reassigning button functions is a breeze, as is connecting a Garmin 1030 bike computer. The hidden buttons on each brake lever are now assigned to scroll through the pages on the GPS device or take me swiftly back to the maps page, depending on if I tap or hold the buttons.

With the latest version of Di2, Shimano have ironed out any previous technological barriers to converting to electronic shifting. Finally, the reliable connectivity we expect in the rest of our lives has come to the bike industry.

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