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Shimano XTR Di2 Long Term Review: Where It Beats SRAM AXS and Where It Doesn’t [Video]

Words & Photos by Jared Erickson

We all know Shimano was a little late to the wireless shifting party. However, sometimes being fashionably late is better than being the first one to arrive. Was Shimano onto something all along?

Introduction

I’ve been riding Shimano’s XTR version of their latest Di2 wireless drivetrain for nearly 1,000 miles and I've formed some thoughts and opinions on its performance and how it stacks up against the other big S. With that in mind, I have also ridden pretty much every drivetrain between the two major manufacturers in the last 10 years, so I'd like to think that gives me a little bit of a soapbox to stand on and maybe even a little credibility to boot.

SRAM shocked the bike world when they dropped the f irst version of their AXS drivetrain back in 2019. It was as if your bike was shifting with magic alone. In 2025 when Di2 was released, with the likes of AI and all sorts of other technological nonsense, we have been slightly desensitized to incredible engineering feats. As you would expect, Shimano’s rollout of this latest drivetrain was welcomed with plenty of comments of the likes of “6 years too late” or “nice derailleur hanger”. It’s easy to mock how long it took Shimano to release this wireless shifter and derailleur… until you actually ride it. In this review, we’ll evaluate each individual component and how it performs.

Shifter

Shimano wanted to create an ergonomic shifter that felt intuitive from the get-go, and in my opinion they absolutely nailed it. I wholeheartedly believe that if you put a mountain biker on a Di2 equipped bike, they will know exactly which shifter paddle does what, right off the bat. That isn’t something you could necessarily say about AXS, aside from t he now old school rocker paddle they dropped back in 2021, which offered a slightly more traditional feel as opposed to the original paddle design. My XTR shifter as well as the XT shifter have the ability to adjust the position of the paddles, and that is a nice little feature they’ve implemented to tailor the shifter to your ergonomic preference. The Deore level shifter has omitted the option to adjust the shifter paddles, but I’m willing to bet that most people would be happy with the configuration it comes with. As far as battery life is concerned, I have yet to replace the two CR1632 batteries in the shifter and they have proven to have great battery life.

Another feature that I appreciate and other Shimano riders will be familiar with is the ability to double shift either up or down the cassette, similar to how you can double shift into a harder gear with a Shimano mechanical shifter. You can simply tap the shifter paddle for a single shift, hold it in that position to continue shifting until you let off the paddle, or push past the single shift for a double shift. This is a great feature when you are trying to quickly dump a few gears or if you’re about to drop into something steep and need a harder gear. I use it all the time. It typically doesn’t result in as buttery smooth of a shift as just a single shift, so I try not to do a double shift under heavy load, but that seems pretty self explanatory. Speaking of features, the third button on the shifter can be used to either micro adjust the drivetrain or you can program it to control external devices like a Garmin head unit.

Derailleur

The lack of a full mount derailleur may cause some people to think that Shimano missed the boat and is a little behind the times. But are they really? There are tons of bikes out there that people are still riding that utilize derailleur hangers that are not of the UDH variety, and in my opinion, there’s nothing wrong with that. This Di2 groupset has the best shifting performance I've experienced of any groupset that uses a derailleur hanger, and surely there are plenty of people who are still skeptical of using a full mount derailleur on their bike, or actually prefer having b-tension and limit screws.

When we had our friends from Shimano on the MTB podcast, they provided us some insight into the development process of Di2 and they had mentioned that they were already far along in their development when they learned that T-Type and full mount derailleurs were being released, so they weren’t able to adapt to that mounting style in time. But I think it’s a blessing in disguise. I’ve had no issues with shifting performance and I do like the traditional mounting style as well, even if the derailleur isn’t quite as flush with the frame as its SRAM counterparts. Even with that said, I’ve yet to smash it on any rocks as I try to avoid doing that.

An aspect of this derailleur that is somewhat controversial and has yet to stand the true test of time is the lack of a traditional clutch mechanism and the spring that has replaced it. Its the cause of the infamous chainslap that this groupset gets a lot of flak for, and is one of the areas where I think T-Type has the upper hand. Those T-Type derailleurs-electronic and mechanical-have an impressively strong clutch which allows the bike to remain as quiet as a mouse when the trail gets rocky and rough. In my experience, the shorter cage of the GS derailleur benefits from this spring clutch design more than the longer SGS version, as the longer cage puts more leverage on the spring and makes it work harder. Perhaps an updated version of this or a stronger spring will help solve this issue, but I’m not holding my breath. If you're riding smoother trails and have this installed on a shorter travel bike, you probably wont notice the chainslap as much as if you had this drivetrain installed on a longer travel bike and you're riding it on trails with lots of chundery sections and big compressions.

I do appreciate how you can simply swap the lower cage on the derailleur and run either the 9-45t cassette or the 10-51t cassette depending on your preference, although swapping the cage is kind of a two person job, or at least it helps to have an extra set of hands or maybe a vice to swap it over. It’s not as fool proof as swapping the lower cage on a SRAM derailleur, as you need to wind up the spring as you install the cage into the derailleur. With that said, I’ve done it a few times now, and It’s not too bad of a job that can be done in just a few minutes.

The battery life of the derailleur has been very impressive. These Shimano BT-DN320 batteries have a slightly larger battery capacity than the SRAM AXS Batteries (300 mAh vs 305 mAh/310 mAh) and I have yet to be stranded on the trail, but then again I am typically charging the derailleur battery every other week or so and I’m riding this particular bike around 3-4 times a week. The argument for having more batteries on your bike and more things to charge isn’t really a big deal for me. Maybe if you are traveling and camping and stuff like that it could complicate things a little more, but if you are just riding it like a daily driver then it just adds another 30 seconds to pop the batteries off the bike and onto a charger and vice versa. It's also a good idea to swap out the coin cell batteries once a year or so, or keep a couple in your emergency kit just in case. Compared to the amount of time I normally spend messing with barrel adjusters and cables and all that, I’m willing to accept that tradeoff. Some bikes are nice to have as fully analog, like an enduro or downhill bike, but for me, when you are riding an XC or trail bike that's doing a lot of miles, I really love the ease and the whole experience of an electronic drivetrain.

Cassette

I really do appreciate how Shimano has offered the two different cassette and derailleur options with this new groupset, and I’ve found myself spending the majority of my time on the 9-45t configuration. It still offers a 500% gear range, and works quite well on a light XC bike like my ASR. I ran it for a little while on my SB140 and it worked well on there as well with a lighter wheel and tire combo, but when I had beefier wheels and meatier rubber on there, I opted for the 10-51 option so I could more easily winch up the nastiest of climbs. Shimano utilizes a combination of materials on the cassette to optimize the durability and weight of the component, and in that regard I think that is very clever.

My experience with the XTR cassettes has had it's highs and lows. The gripes I have with these cassettes is that all of the separate cogs introduces the possibility for it to creak, come loose, or, at least in my experience, just simply make it more prone to having issues compared to a one piece cassette. I’ve had to re-tighten it a couple of times (which I've never had to do with a SRAM XD cassette) and it develops some creaks from time to time. It’s not the end of the world, you’d just hope that you wouldn’t have to deal with stuff like this on a premium product like XTR. After running SRAM cassettes for years, I have really come to love a one piece cassette, plus the ease of installation of a cassette on an XD driver - I feel like there is some room for improvement when it comes to a splined freehub body.

Crankset

A crank is a crank, right? Pretty much, as long as it doesn’t break or have your pedal snap off. Thankfully, neither of those things have happened to me with these XTR cranks. My mind is still wrapping itself around how they even make these hollow forged specimens, but that is neither here nor there. These XTR cranks have shown impressive durability and are seemingly as stiff as you’d want or expect, and as far as weight is concerned, they are at least comparable to other popular carbon cranks and perhaps even surprisingly seem to have good value. They are still running the classic hollowtech II spindle interface, and if it aint broke, don't fix it. I have been riding the 165mm XC version of the XTR cranks and I have really come to love the shorter crank arms. It’s amazing how just a few millimeters can have a drastic effect on how frequently they come into contact with rocks while climbing up a techy trail. They have some nice protective material installed which keeps them looking fresh for miles and miles.

I’ll admit, I was skeptical of the Shimano style crank preloader that uses a weird little tool (apparently you can combine an 8mm & a 5mm and use that in a pinch instead) as well as the pinch bolt onto the spindle, but I’ve had zero issues with either of those during my time using it. I also don’t love how the chainring requires a specific tool to remove or tighten it, which just adds another tool that you need to have. Out on the trail, there’s really nothing wrong with these cranks at all and they have had zero issues, so in that regard they are certainly a solid piece of equipment and they have that nice premium look to them. I have been loving the 165mm length, and really appreciate how I never smack the cranks on rocks while climbing.

Chain

Shimano may not make blinged out chains like SRAM does, but where they skimp on bling factor they make up for it with their Hyperglide technology. The smoothness of shifting under load is seriously impressive. On plenty of occasions I’ve experienced incredibly smooth shifts under full load whether it’s climbing or sprinting. If I were to fire off some of these shifts with a first gen AXS drivetrain, I would turn myself into the police for domestic drivetrain abuse. XTR Di2 takes them in stride and seems to thrive on shifting under load. Full disclosure and to be fair, I do love AXS and it does work quite well - I have it installed on my OPEN U.P. gravel bike and it shifts quickly and smoothly especially when you are putting out a consistent cadence and power. Back to the chain talk, I’ve had zero issues with these Shimano chains and they have proven to have excellent durability and I’m not sure what sort of black magic they are adding to them but it sure seems to help the drivetrain have seriously smooth shifts.

Final thoughts

So, all things considered, does wireless Di2 have a place in this modern mountain bike world? It absolutely does - it is incredibly easy to install and set up, it shifts extremely quickly, consistently and smoothly, and the shifter is incredibly ergonomic and satisfying to use. It’s proven to be durable, and there is certainly a cohort of riders who will appreciate the continued use of external adjustments like limit and b-tension screws. Yes, there is a bit of chainslap on chattery trails and big impacts, however, the short cage version isn't as bad as the long cage, and isn't as noticeable on my xc bike on less brutal trails. All in all, I think this is a great upgrade for those who are skeptical of full mount derailleurs, have bikes without a UDH and want incredible wireless shifting performance, or who already have Shimano mechanical and want a wireless upgrade.