Automatic and Pedal-Free eMTB Shifting - Shimano's E-specific XT Di2 Drivetrain Deep Dive 8

Last June, Shimano unveiled three new e-specific Di2 groupsets and two motors that seemed to slide under the radar of most mountain bikers. At the time, the industry was still caught up in the craze of Covid delays. With components not expected to hit the market for months, we didn't read much into everything Shimano was launching other than posting the press release. Fast forward to now and bikes are beginning to ship with new drivetrains and motors. Lucky for us, we had the opportunity to join Shimano to experience first-hand how the new Di2 components integrate into their STEPS e-ecosystem while leveraging Linkglide technology to deliver bulletproof shifting and new features like Auto Shift and Free Shift.

Highlights 

• E-bike-specific electronic shifting
• Only compatible with Shimano EP801 or EP6 motors
• 11-speed and 12-speed options 
• Optimized around Linkglide shifting technology
• Power is supplied directly from the e-bike battery
• New XT Di2 Shifting Switch with three buttons
• Free Shift (shifting without pedaling)
• Auto Shift with Manual Override
• Updated features and layout of the E-TUBE App
• Only available as an OEM spec

Product Overview

It's no secret that Di2 has not been accepted with open arms by the mountain biking community like other electronically operated drivetrains. While Di2 has trickled down to the 105 groupset in the road bike market, the latest XT and XTR launches were absent of any electronic shifting. Shimano knows Di2 has room to improve, and the plan has always been to continue advancing their electronic components for more than just road and e-bikes. But, for the time being, Shimano identified an obvious opportunity to integrate Di2 into their STEPS e-bike platform, combined with Linkglide shifting technology, that opens the door for features only possible with electronics.  

There are three new Di2 derailleurs optimized to integrate only with Shimano's latest EP801 or EP6 motors: CUES 10-speed (commuter/lifestyle focused), XT Di2 11-speed, and XT Di2 12-speed. The 10- and 11-speed derailleurs use Linkglide shifting technology, while the 12-speed uses Hyperglide+. This is an important difference because Linkglide is the special sauce that enables the Auto Shift feature — that's right, automatic, hands-free shifting. The 12-speed Di2 Hyperglide+ derailleur can only be used with e-bikes but does not feature Auto Shift while pedaling, only when coasting (Free Shift). We rode the XT Di2 11-speed drivetrain, so we will only focus on the technology and features it provides below. Regardless of the Di2 drivetrain system you choose, the derailleur and Shift Switch are still wired but now receive power directly from the e-bike battery. Like existing Di2, everything can be customized in Shimano's E-TUBE Project App. A new Shift Switch also features individual paddle adjustability and a third button to toggle between Auto and Manual shift settings.

Linkglide Shifting Technology 

Highlighted extensively during the CUES brand launch, Shimano's latest Linkglide shifting technology prioritizes durability and long-lasting shifting smoothness. All Linkglide components, regardless of the number of gears, use Shimano's existing 11-speed chain. Linkglide cassettes feature all-steel gears with wide, taller teeth that are steeper on the leading edge and chamfered on the falling edge. This design drastically improves wear in high torque situations and improves the life of the cassette by more than 3X compared to the previous Hyperglide. Additionally, the shift gates on Linkglide cassettes are super robust and act to push the chain down to the next gear in one motion, minimizing pedal shock.

By comparison, Hyperglide+ cassettes do function well under load, but since they use normal-width teeth, they are more susceptible to deforming under the torque of an e-bike. This reason alone restricts the 12-speed Hyperglide+ Di2 derailleur (and accompanying Hyperglide+ cassette and chain) from being Auto Shift compatible. Since automatic shifts constantly occur under the heavy torque of the motor, the odds of deforming teeth were too high for Shimano to guarantee long-term quality shifting with Hyperglide+. 

The downside to Linkglide is that it's heavier and shifts slower than Hyperglide+. However, when applied to e-specific Di2, we don't see a reason to pick Hyperglide+ since weight isn't a significant factor on a 50-pound e-bike and Auto Shift wouldn't be an option. For reference, the Linkglide LG700 11-speed cassette weighs 609 grams (11-50T), while the Hyperglide+ XT M8100 12-speed cassette weighs 470 grams (10-51T).  

Shimano EP801 and EP6 Motors

XT Di2 is only compatible with Shimano's latest EP801 or EP6 motors. The EP6 is slightly heavier (about 300g), but both deliver 85Nm of torque via Shimano's dynamic assist curve. What separates the new motors from the existing EP8 drive unit is connectivity with Di2 components and the ability for the front chainring to spin without pedaling. There are also new CAN and ACC ports that open the door for two-way communication between Shimano STEPS components and third-party components, such as batteries, assist switches and displays.

To motivate people not to hack their e-bikes, Shimano equipped both motors with sensors to detect when someone attempts to tamper with the system (e.g., increase the speed limit). After three attempts, the system will enter a Safe Mode and will not provide any assistance. Freeing a bike from e-Jail is handled by a Shimano sales office or distributor for a fee. If you really feel like trying to squeeze some extra juice out of your full-power e-bike, consider buying a Surron instead. 

Shimano Auto Shift

Shimano's automatic shifting roots run deep, dating back to 1997 with their AUTO-D cadence-based internal hub system. Now, over 25 years later, Auto Shift is easily the most fascinating aspect of the new e-specific Di2. And there are way more factors than just cadence dictating when shifts occur. Auto Shift uses an advanced algorithm and multiple sensors to continually measure cadence, rider input torque, rate of acceleration, and speed to select the best gear. A lot goes into each automatic shift, but to generalize the experience, as you ride, the system downshifts to easier gears when speed and cadence slow and torque increases. When cadence increases and torque drops, the system shifts into harder gears. Automatic shifts can occur when pedaling and coasting, and riders always have the option to throw in manual shifts if desired. 

Setting up Auto Shift is crucial to creating a shifting experience that matches your pedaling habits and preferences. Within the E-TUBE PROJECT App, there are three adjustments available: 

Shift Timing: This adjusts the target cadence range of the system by factoring in the motor torque, speed, cadence, and the rate of change of each factor. Shift timing comes set at 72 rpm, which Shimano says will complement most riders' pedaling habits. Riders can adjust between 50 and 100 rpm, and a higher number will cause the shift range to function around a higher cadence, while a lower number will have an adverse effect. Shift timing can also be adjusted on the display unit while riding and only needs to be changed by small increments to have an effect.

Climbing Response: This sets the torque threshold at which the system will shift into an easier gear. There are eight response settings. A higher number increases the threshold, requiring more rider torque to cause a shift into an easier gear, while a lower number decreases the threshold, requiring less rider torque to cause a shift into an easier gear. Put another way, a climb response of 8 is less responsive and shifts less often, while a climb response of 1 is very responsive and shifts more often.   

Start Gear: The gear the system shifts into when slowing down and coming to a stop. This adjustment exists so the system doesn't shift into your easiest gear as you slow down.   

Auto Shift can be turned off entirely or set only to operate when coasting (Auto Free Shift). This can be done in the app or with the Shift Switch's third button.  

Shimano Free Shift

Free Shift is simply pedal-free shifting made possible by the Di2 derailleur and EP801 motor talking together. It allows riders to change gears up or down the cassette while coasting. This feature can be taken advantage of manually, and Auto Shift also uses Free Shift to select the right gear when not pedaling.

E-TUBE PROJECT App Updates 

On top of the three new Auto Shift adjustments, the E-TUBE App now features a Basic and Fine Tune mode. Basic mode maintains the classic three customizable assist modes (ECO, TRAIL, BOOST), while Fine Tune mode gives riders up to 15 customizable assist modes. Assist character, max torque and assist start remain the only adjustments available. However, the highest assist character level is higher than before, meaning the motor will deliver power faster than before in the highest setting. Our favorite update to the app is the addition of an assist curve graph that clearly illustrates the difference between each assist mode and how adjustments affect each mode. 

On The Trail

Two weeks ago, I joined Shimano for a Di2 media camp on the island of Krk, off the coast of Croatia. Located a few islands from Lošinj, where the downhill World Cup was held in 2018, Krk probably isn't on anyone's list of must-visit riding destinations. Known more for its olive oil, ancient city streets, and summertime beaches, the terrain was relentlessly rocky, descents were low-angled and short-lived, and climbs didn't require much precision to clean. While not the most engaging or fun trails, I thought they were perfect for testing the abilities of a drivetrain. I was able to let my riding take a backseat and just focus on analyzing how the various shifting technologies performed.

Shifting Under Load - Linkglide Delivers

If Auto Shift and Free Shift are the stars of the show, Linkglide is the producer behind the scenes, making everything happen. After two long days of riding, I was blown away by the shift quality, consistency, and precision of Linkglide in high-torque scenarios. Shifts were always crisp and definite, delivering constant power as the chain moved between gears. Even when I tried to fluster the system, shifting mid-rock garden under as much load as possible, I never experienced a botched shift. The only outcome of some aggressive shifts at less-than-ideal moments was a loud clang as the chain engaged a new gear. But a noise never resulted in a poor shift or pause in forward momentum. 

Linkglide made me realize how delicately I've been shifting on eMTBs over the past few years. Usually, I time my shifts around high-output maneuvers, easing off the pedals for that split second while the chain jumps to the next gear. It might only be a split second, but it has changed how I approach shifting under the extra torque of a motor. With Linkglide, I could change gears carefree, similar to how I shift on a mountain bike. 

Weight and shift speed are the two main downsides to running Linkglide Di2 compared to Hyperglide+ Di2. Personally, I'm not counting grams on an e-bike and care way more about the durability and functionality of components. For riders trying to build the lightest e-bike possible, shift quality is probably focused on less anyway. As for shift speed, I didn't notice Linkglide Di2 hesitating in the slightest between gears. If Shimano had told me Linkglide made shifts happen faster, I probably would have believed them. The ability to maintain force on the pedals during shifts made switching gears feel near-instant compared to any other drivetrain I've ridden on an e-bike.  

Auto Shift Performance

When you strip back the sophisticated algorithm, sensors, and adjustments, Auto Shift performs as intended, operating in the background as you ride along. Auto Shift is one of those features that few mountain bikers were eagerly waiting to be developed, but it offers a unique riding experience that some will find beneficial. Shimano's ability to intertwine its Di2 technology with its e-bike system to create a feature like Auto Shift is undeniably innovative.      

Dialing in Auto Shift adjustment to match your pedaling preferences is crucial to receiving shifts exactly when you want. There was a lot of information to digest surrounding Auto Shift during my two days in Croatia. While the system shifted when I wanted about 80% of the time right out of the gate, I struggled to achieve that blissful state of unconscious shifting. I messed around with Climb Response and Shift Timing the most, exploring each adjustment's effect. Thankfully, the trails we rode required minimal skill because I've never focused so hard on how one aspect of my bike performed while riding. By the end of our second and final ride, my manual shifts were seldom, and I could ride for long periods without questioning if shifts would occur at the optimal time. 

For a feature that's performance relies heavily on being set up correctly, I will need more time to form a definitive opinion about Auto Shift. Luckily, I will be getting an XT Di2 test bike soon, and I can continue dialing in my setup. It will take time for experienced riders who've manually shifted for years to adopt or accept automatic shifting, and it won't appeal to every rider. Auto Shift offers a different shifting experience, but its functionality is promising when applied to e-bikes, where being in the right gear is less crucial than mountain bikes. For now, I will keep drinking the Kool-Aid and believe the promise of thought-free shifting Auto Shift can provide until I have the chance to prove otherwise. 

Free Shift Performance - Shifting Without Pedaling

While Auto Shift isn't a feature I see myself using every ride, Free Shift became an instant favorite after the first descent. I'm pretty compulsive about being in the right gear for any situation (which is probably why there is still room to improve my Auto Shift settings), and I immediately took advantage of being able to shift at any time, with or without pedaling. Here were some of the most common situations where I used Free Shift: 

1. Braking into a tight corner, I would drop a few gears to be prepared to pedal out at a normal cadence with power.
2. Descending to the bottom of a trail followed by an immediate climb, I would drop a few gears to avoid smashing multiple gears at once. 
3. After pedaling into a descent from a dead stop, my speed would often quickly surpass the gear I reached from pedaling, so I would grab a few extra gears to be able to pedal at speed if needed. 

During sustained descents, Auto Shift usually beat me to the punch and would induce a Free Shift first. When riding undulating trails that would suddenly change pitch or hitting abrupt, tight turns, I almost always had to manually engage shifts to be in the right gear. The time required for the motor and derailleur to shift was nearly instant, and I was never flustered with my shifts because the system was lagging behind my needs. Overall, Free Shift is a feature I see most riders using regardless of terrain or riding style, as it gives the power to always be in the right gear.

EP801 Performance

With the power output and assist characteristics of the EP801 mirroring the EP8 I've ridden extensively, the on-trail performance was identical. Shimano's dynamic assist curve is distinguishable compared to other drive units, with an assist character that turns on the power as you get on the pedals. The only difference I noticed with the EP801 motor was the precise power delivery available with the new Fine Tune mode. Like Specialized's MicroTune feature, Fine Tune mode allowed me to treat the Assist Switch like a shifter to receive the perfect amount of power for different trail conditions. Unfortunately, Fine Tune mode is only available with the new motors.

Things That Could Be Improved

The biggest downside I see with the new XT Di2 is how intertwined it is with Shimano's STEPS system, specifically their latest EP801 and EP6 motors. It's a catch-22 because integrating Di2 technology with the STEPS e-ecosystem is the only way to achieve the drivetrain capabilities Shimano has created. But the fact that XT Di2 is not backward compatible with the existing EP8 motor or any other e-bike platforms means that riders will only be able to receive Auto Shift, Free Shift, and Fine Tune mode by going out and buying a brand new bike specced with the entire system. This poses the toughest predicament for riders who already own an expensive e-bike and want to enjoy the capabilities of Di2. The only option is to start from scratch with a new bike. The one caveat is that riders can equip any current e-bike, Shimano motor or not, with mechanical 11-speed XT Linkglide to receive the same crisp, durable shifting quality as XT Di2. 

I left Croatia a little frustrated that I couldn't make Auto Shift function exactly when I wanted. For a feature that relies so heavily on proper setup, Shimano missed the mark on the information surrounding the shift timing and climb response adjustment. I kept thinking, if I'm struggling to get Auto Shift dialed after two days of one-on-one testing with the fine folks from Shimano, how many riders will be worse off than me when they pick up their new bike? I know they plan to release numerous communication assets that clearly explain each adjustment function and how to correctly apply on-trail feedback in the app, which will help tremendously. 

Long Term Durability

More than two days are needed to test anything, especially drivetrain durability. With generous claims of long-lasting shifting, I'm excited to log many future miles on our Linkglide Di2 test bike. If it's any consultation, during the press camp, we were joined by legendary racer Mick Hannah who spent last year's E-EWS season testing XT Di2. Mick is no slouch when it comes to unleashing superhuman watts, and he said that in the past, he might go through a few Hyperglide+ drivetrains during the offseason. This offseason, he's ridden the same Linkglide Di2 drivetrain. Sick Mick approved.  

What's The Bottom Line?

The cross-pollination of Shimano's STEPS e-ecosystem with their Linkglide and Di2 shifting technologies has spawned an e-bike drivetrain with unmatched high-torque shifting performance and never before seen shift features. Free Shift and Auto Shift offer unique and exciting characteristics that will change your shifting habits on an e-bike. However, only time will tell if the benefits of automatic and pedal-free shifting become accepted as the new norm for e-bike drivetrains. And with XT Di2 availability confined to just complete bikes for the foreseeable future, it will likely be a while before we are all zipping around on e-bikes without shifters.

About The Tester

Jason Schroeder - Age: 28 // Years Riding MTB: 16 // Height: 6' (1.8m) // Weight: 175-pounds (79.3kg)

A once-upon-a-time World Cup downhill racer turned desk jockey, Jason has spent years within the bicycle industry from both sides of the tape. A fan of all-day adventures in the saddle or flowing around a bowl at the skatepark, he doesn't discriminate from any form of two-wheeled riding. A SoCal native who doesn't spend too much time in any single place, you can find Jason camped out in his van most weekends somewhere on the West Coast.