Automatic shifting is probably something that most mountain bikers don’t give much thought to. After all, modern 1x drivetrains aren’t exactly mentally taxing to operate, and with a minimum of practice, smooth shifting becomes second nature. But what if you didn’t have to touch the shifter at all during a ride? Or what if a bike was set up to automatically shift gears when you were coasting and engage the correct gear when you started pedaling again?
Both scenarios are possible with Shimano’s latest XT Di2 Linkglide electronic drive train, which was specially developed for e-bikes. The groupset was announced at Eurobike last year, but it’s only now appearing on select bikes. I was able to try the system for two days, enough time to get an idea of how well the concept was implemented and which aspects are most relevant for mountain bikers.
The basics
As already mentioned, the new XT Di2 drivetrain is only compatible with e-bikes with Shimano’s 600 or EP801 motors. It’s powered by the same battery that provides the pedal assistance, meaning there’s no need to charge a separate battery… but it also means it’s not wireless.
The system can be configured in four different ways.
Full manual shifting is exactly what it sounds like – the system only shifts when either shift lever is pressed.
Fully manual shifting with Free Shift engaged allows for idle shifting – the motor rotates the chainring forward while the cranks remain stationary, and the derailleur moves at the same time, allowing you to select the ideal gear for an upcoming terrain change without doing so to have to pedal.
Automatic shifting in sail mode requires manual shifting when the cranks are turning, but the automatic shifting system takes over when they are stationary and the bike is moving.
In fully automatic mode, the computer takes charge and the derailleur shifts into the appropriate gear based on information gathered by sensors in the engine. Things like cadence and speed are taken into account and the algorithm decides when to shift. A decent amount of customization is available in this mode, designed to help riders customize the automatic shifting to suit their preferred pedaling style.
To add to the confusion, there are two versions of the powertrain, XT Di2 Hyperglide+ and XT Di2 Linkglide. Hyperglide+ is the lighter option, based on a 12-speed, 10-51 tooth cassette. It doesn’t have the fully automatic shifting option, although it can be configured to shift automatically while a rider is coasting, and manual shifting while coasting is also possible.
Fully automatic shifting while pedaling and coasting is only available with the Linkglide drivetrain, which uses an 11-speed, 11-50 tooth cassette.
Set up
One of the biggest hurdles the system faces is the amount of experimentation required to customize it for each driver. I can see the setup process being daunting for a beginner, which is also the type of rider who would be most likely to use the fully automatic setup.
Shimano’s app allows you to adjust two different settings – shift timing and response when climbing. The shift timing adjusts when the computer decides to make a shift. Riders choose a numbered setting between 50 and 100 (Shimano says 72 is a good place to start) and then adjust accordingly based on how the response feels on the trail. This number doesn’t directly correlate to cadence, but the higher the number, the faster the cadence will be.
Climb Response sets the torque threshold for a shift. Basically, when you pedal hard, like on a climb, the drivetrain shifts to an easier gear. Selecting a higher number (there are 5 levels) for the Climb Response will allow more time before shifting to an easier gear is initiated. It’s worth noting that a sudden stomp on the pedals, like when you’re sprinting out of a starting gate, will make it want to shift into an easier gear. That’s not exactly the ideal scenario when you’re trying to squeeze out as much power as possible. So if you race or tend to sprint everywhere, manual shifting while pedaling might be a better choice.
The final setting involves selecting a starting gear. This is the gear the system shifts into when a driver slows down. Imagine stopping at a crossroads. What gear do you want to be in when restarting? Most likely this is the best choice for a starting gear. It’s also the gear the system is likely to be in after slowing down for a tight corner or technical section of track.
driving impressions
So how well does it actually work? Better than I expected to be honest, although I wouldn’t say it’s 100% perfect – I still regularly used the shifters to fine-tune the gear selection when the system wasn’t behaving the way I wanted it to. However, there were several instances where it was really impressive. A certain section of the trail had a flat approach to a fairly steep slab of rock, and I was able to leave the shifter alone while the derailleur shifted the chain into the appropriate gear as I climbed, executing the shifts exactly when I had on my own. It also happened that when descending, I heard how the chain switched to another cog, and then I was able to step out of a turn with the bike already in the right gear.
Even after some tweaking of the settings via the app, there were still moments when I pedaled in a harder gear than necessary or shifted the system at an inopportune moment. To tweak it even further would require more experimentation on a wider variety of terrains – I’d have to do repeated laps on the same section of track to get it closer to the shifting experience I was looking for. As I mentioned in the setup section, the amount of tinkering required to actually dial it in seems quite high.
Aside from the automatic part of the shifting, the actual shifting feel of the Linkglide cassette was very good, especially under load – I would totally agree with Shimano’s claim that it’s smoother than the Hyperglide+, which already worked well under power.
I feel like Shimano came up with the automatic shifting algorithm, realized it worked well, and is still trying to figure out where to implement it. Realistically, I think electric commuter bikes are the ideal use case – I can see riders who have never ridden a modern bike appreciate the fact that they don’t have to go through the nuances of the modern bike on their way to work or to the grocery store have to think about switching. Shimano has auto-shifted in this area before, but this is by far the best iteration of it.
The good news with this technology is that it’s not an all-or-nothing proposition. Riders who buy an e-bike with XT Di2 can decide which mode best suits their needs, rather than being tied to one setting. Personally, I would probably use the fully manual shifting with Free Shift the most, and I have a feeling many mountain bikers would appreciate that right away—there are all sorts of scenarios out on the trail when being able to shift while coasting can come in handy prove
It will be interesting to keep an eye on this system and see where the technology goes. Personally, I’m more curious to see how Shimano will react to SRAM’s geared drivetrain, but in the meantime I’ll probably keep myself playing around with the thousands of different motor and shifter settings to see if I can unlock a combo that works well enough to convince me to let the computer take over and make all the shifts.
