Shimano XT Di2 M8250

Let’s get right to it. The new Shimano XT stuff? It’s good. It shifts with precision and speed. The brakes feel like Shimano XT brakes, but they have a bit more power than before. The cranks offer that correct mix of weight, strength and price, but are a little bit simpler to install than in the past. The wheels…I mean…the wheels are aluminum wheels. They’re not super light, they seem to be holding up pretty well, the new hubs have cartridge bearings in them.

So, if you’re looking for the quick and dirty on the new XT stuff, that’s it. Simple. Dependable. Functional. There are a few more technical details and prices here in the first look, but if you’re just need a quick yay/nay on a new bike with an XT build, I’d give it a yay.

Of course, there’s more to it than that. There’s so much going on with the new XT stuff that I can and will talk about it at length, but that doesn’t exactly slot into the classic bike part review framework. So, with our overall conclusions out of the way, let’s look a bit more deeply at some things that allowed for this to happen.

Why should you buy an electronic drivetrain?

I mean…should you? They certainly cost a lot of money, and put a lot more dollars at risk every time you hit the trail. I just had a quick look back at the MSRP pricing (which I didn’t do a great job of providing in the first look) and it isn’t pretty (860 USD for an upgrade kit, which gets you a shifter and a derailleur, 570 USD just for the derailleur and 190 USD for the shifter). This is a huge premium over similar level mechanical components.

At the risk of strawmanning a little bit, there is a faction that insists electronic drivetrains are nothing more than an expensive way to do what a mechanical drivetrain already does. This is an acceptable take. Maybe even true. Mechanical drivetrains work really well, and we went many years without needing batteries and FCC certification to ride our bicycles. If you’d have asked me a year ago which drivetrain to buy I would not have pointed towards anything electronic.

Then a funny thing happened. I rode an electronic drivetrain for a while. This was fine. Everything worked as it should. I wasn’t totally blown away, but I was happy enough. And then I went back to my old bike.

At the time, my old bike was equipped with that TRP drivetrain, and my one major complaint about that system was that it had a tendency, when grabbing an easier gear, to overshift one extra cog before settling back to the one you actually wanted. This was manageable, yet annoying.

Re-experiencing that drivetrain was terrible. I found myself overshifting every single time I grabbed an easier gear. I started wondering how I had gotten my review so wrong and, after two rides, yanked it off the bike and went back to the stock (mechanical) XT drivetrain.

In my TRP review, some people noted that you can overshift a Shimano drivetrain as well, but this was not something I experienced, or at least noticed experiencing. But then all of a sudden it was happening with the XT system as well! While not as bad as the TRP drivetrain, I was overshifting when I grabbed an easier gear with some frequency. I’d forgotten how to properly shift my bike!

This is the problem with the human experience. We very quickly adapt to new things, and we often don’t know how different two things are until we go back to the first thing and experience it again! My mind would likely adjust after some more time, but the point is that my mind would have to adjust! I had just created overwhelming evidence for myself that electronic drivetrains work differently, as well as a solid argument that they shift better and are easier to use. Oh no!

This isn’t to say that you need to throw your mechanical drivetrains in the garbage and fork out thousands for the newest electronic gizmo. There are still downsides to these things (cost and having to keep batteries charged being the main ones)! But it’s becoming much harder to claim that there is no benefit to electronic drivetrains and only downsides.

The derailleur

Being first to market can leave your competitors with challenges. You can take the most obvious solution, patent it, and watch your competitors flounder. Who would have thought that battery placement would cause this?

Figuring out a way to place a battery on the derailleur turned out to be one of the defining parts of this whole new Di2 system. Placing the battery within the parallelogram is not only the key to the system existing in the first place (rumours of SRAM battery related patents holding things up for Shimano have proven to be true), but also lead to (what Shimano feels are) durability improvements. Carving out a spot for the battery lead to widening of the parallelogram and the whole wedge shaped derailleur concept.

While on the subject of durability, let’s talk mounting. SRAM has famously differentiated themselves here with their “full mount” system that does away with the traditional hanger. Shimano sticks with the classics here, and has the same mounting system as the derailleur on the 1994 GT Karakoram hiding out in the back of your garage. Is this a good thing? Bad thing?

As space between cogs get tighter, there is something to be said for reducing the number of things that might have an impact on your shift quality. While it is pretty trivial to straighten out a hanger if you have the correct tools for the job, this isn’t something you need to worry about with a full mount derailleur. A consistent mounting point for rear derailleurs makes a lot of sense.

Worse (for Shimano), the initial worst case fears of the full mount system have not come to pass. There hasn’t been a rash of broken frames because of the elimination of the hanger weak point. At the same time though, I don’t think full mount has been the absolute set-it-and-forget it system that SRAM promised, and when something goes awry it can be difficult to know where to start with troubleshooting. When I borrowed a Norco Range for Megavolt the shifting was dreadful and all I could do was look at it and wonder.

So, there’s something comforting about just screwing a derailleur onto a hanger like we’ve always done, and I’ve never been overly scared by limit screws or adjusting my b-tension. I feel even more strongly about this as full mount pushes into the gravel sphere, but let’s not worry about skinny tires here today. How my derailleur mounts to my bike won’t determine if I buy it or not, but at the same time wouldn’t it be great if we could split the difference of the two systems somehow? Don’t ask me what that looks like.

What we wind up with is two different philosophies on how to make a robust system. SRAM has gone brute force, engineering out any supposed weak points in the system, and bolted that sucker straight to the frame. Shimano has bulked up in some key areas (as we will see below), and then focused on deflecting away any impacts via shape, placement and internal trickery, but still relies heavily on a skinny piece of metal.

The next major change/difference in this derailleur (and arguably the largest surprise) is the elimination of the clutch, and the use of a stronger dual spring pivot to reduce chain movement. While clutches were a major step forward in keeping our chains in place, they aren’t without their issues. As the story goes, Shimano found that many derailleurs out in the field had poorly adjusted and/or poorly working clutches, concluding that having a somewhat delicate (and plastic enclosed) mechanism on the leading edge of the derailleur isn’t the best idea.

Further (and less anecdotally), the very existence of the clutch created space constraints which lead to compromises in other areas. Shimano feels like the new dual spring system will work as designed for longer, as well as increase the durability of other parts within the system. It won’t require any adjustment, and will allow for increased wall thicknesses in key areas.

While this sounds great in theory, I had questions about how it would work in practice. This sounds a little bit like a fork manufacturer removing the damper and bumping up spring rates to compensate for blown dampers. A clutch is almost like a damper to the system, adding friction so that the derailleur doesn’t move around as much. A spring isn’t dissipating energy, it’s just making it harder for the derailleur to move in a particular direction and creating a lot of potential energy in the process. Once it does start to move, that potential energy wants to send it quickly back to where it came from.

This became noticeable over fast, repetitive hits. It would be interesting to see on a high speed camera if this is “worse” or just “different” than what we’re used to. I wouldn’t be all that surprised if the chain was settling more quickly, but with sharper feedback at the feet (but that’s total speculation). As we become more conscious of chain feedback on suspension systems, this is something to think about. I did ask Shimano about this, and they weren’t surprised by the question. They stressed the benefits of changing the system and pointed out that there were other means to control chain feedback (Ochain, STFU, chainguides) as required.

I also asked Shimano about shift speed and electronic controls. With a single shift, the derailleur moves as quickly as possible, and at a much faster rate than a mechanical system. It’s only when you do multiple shifts (and this is different in e-bike vs regular mode) that the electronic brains slow things down. Either way, I found shifts to be lightning quick, to the point that I was much more likely to go for a quick little one gear shift on flat spots in climbs and the like.

Finally, we’ll end where we started, with the battery. I found battery life to be excellent, to the point where I stopped worrying about it altogether. Ride after ride, it just always seemed to have life left in it, and I never seemed to get close to having the battery die. I took to charging it every several rides just because. Shimano claims an estimated range of a very specific 338 km (210 miles) of mountain bike riding per charge.

The Shifter

Most launch articles told you all that you need to know about the shifter. It looks and acts much like a traditional Shimano mechanical system, and that’s a pretty great thing. Shimano did experiment with new concepts, but found that most people preferred the feel of the classic system of yore. And I agree. This system is intuitive and easy to use.

My one nitpick with the shifter is the i-spec mounting system. I really don’t like integrated shifter mounts and much prefer the flexibility of a separate clamp, bar clutter be damned. Looking at photos of my setup, I think my problem is that my brake levers need to move inboard, as I’ve had to move the shifter as far back/up as possible to keep some thumb clearance. It would be trivial to put this in the right place with a separate clamp, but the range of the i-spec mount is limited. Worse, it’s really hard to reach the bolt that holds the shifter in place. None of my on trail tools fit, so it became a workshop job to adjust, which is a bit annoying when you’re on trail and realize that the angle isn’t right. Any standard L-key is going to work, but that’s not something I often have trailside.

Beyond that, the system works flawlessly, and is an easy win compared to a SRAM pod. The levers feel great and this feels like the logical extension of our years-and-years of shifter advancements.

The Chain, the Cassette, and Hyperglide+

While there isn’t a new chain, there are things to talk about here. Honestly, I don’t think I ever clued in to what Shimano was up to with “Hyperglide +” vs. “Hyperglide.” I remember some talk of different shift ramps and some indication that they drove the chain both up and down the cassette, but that always just felt like words rather than an explanation of what was happening. I’m still not all the way there to understanding how this works, but after my conversation with Shimano I have a better idea and a lot more curiosity.

This is a thing about bikes that annoys me quite a bit. We ride around with all of this technology, but there’s often not a great explanation as to why something works. For a suspension component, we’ll be lucky to get a confusing oil flow animation. For shifting, there often isn’t anything. These cassettes cost a small fortune and we just have to imagine that all those intricately carved profiles actually do something. But what?

During my conversation with Shimano I had to stop and catch my breathe a little bit. They presented me with a concept so simple, I felt a bit stupid for taking this long to realize it.

A fast shift isn’t really about how quickly your chain moves side to side, it’s about how quickly your chain is seated on the next cog, driving your bike forward.

I mean, come on now! Of course it is! Yes, lateral chain speed is important, but if it isn’t engaged on the cog, it doesn’t matter how fast it moves. So, that is the main difference between Hyperglide and Hyperglide+, and surprisingly, much of that comes down to the chain.

Details become a bit murky again here, and I’d love to spend some more time digging into this. What Shimano says is that the key (or one of the keys) to the whole system was extending the inner plates of the chain. This is why you need a special chainring for your 12 Speed Hyperglide+ system, and why you might have some struggles if you mix and match drivetrain components. The idea is that with the extended inner plates they figured out a way to make it so the chain remains in contact with the cassette through the shift. The chain is essentially already on the next cog before being released by the previous cog, and somehow the geometry of the chain with the extended inner plates allows this to happen.

Details on what this means aren’t all that forthcoming. To start on our road to understanding, I’ll point you at a couple of things from Shimano. First, here is this simple little diagram showing what they’re talking about when they say “extended inner link plates”.

Next, is this video showing the comparison of a Hyperglide with a Hyperglide+ shift. While this video is likely an idealized situation, it does match my on trail experiences and goes a long way to explaining why Hyperglide+ felt like such an improvement in shift quality over Hyperglide. It wasn’t just a “+” sign, after all!

Looking beyond the chain, Shimano indicated that one of the other big improvements was that one tooth on the cassette that is a bit longer. This teensy bit of extra height on particular cogs is what allows for the chain to be held onto during a shift. Or is that what picks it up first? Again, unclear. But it’s doing something!

The video below does a nice job of showing some of these differences.

Brakes

I find that it is pointless to draw sweeping conclusions about differing brake systems. Temperature, weather, trail conditions, braking style, pad condition, pad compound and rotor style are some of many variables we experience with our brakes, and part of why some love what others hate. So, if you’re already a Shimano brake guy, you’ll probably like these. They are an evolution of Shimano brakes with a bit more power, and a few added features.

For me, it had been a while since I rode a pair of XT brakes, back to my back-to-back Ripmo/Spectral experience. Those bikes had the yin and yang of Shimano brakes and only truly came alive when I pooled the best parts from each system. Cheap rotors? No good. Organic pads? No good. Ice techs and metallics? Very nice. These brakes are reminiscent of those times. There’s the same quick bite of power, and it’s really only at the tail end of things (picture squeezing the life out of your levers at the bottom of a chute) where I wanted more power. That’s not all that unusual for a non-DH oriented brake.

At the lever, things look quite a bit different than they used to. The new style of cable routing and the new placement of the reach adjustment dial are very noticeable. Less noticeable is the new pivot placement. This isn’t something that I had thought all that much about until talking to Shimano. Their goal is to get the pivot as close to the bar as they possibly can. The reason for this is quite simple. If you think about your brake lever, it starts angled away from your handlebar (and your fingers). As you pull the lever closer to the bar, the angle decreases. Eventually, the lever gets to be parallel to the bar, or even pointing at the bar if the pivot is far enough out from the handlebar. Shimano feels pretty strongly that this isn’t a good thing, and indeed, on a lever with a pivot placed far out from the bar, you can really feel a difference as the lever transitions through these phases, from pointing away, to parallel, to pointing towards your bar. As well, worst case, with the lever pointed at the bar, that geometry tries to push your finger off the end of the lever.

Things like reach adjust knobs aren’t something that I usually worry too much about. Once you get your brakes dialed in to your preference, you shouldn’t have to tweak these very often. The exception is when I’m swapping back and forth between multiple bikes, where it seems like some small adjustment is always necessary. So, while the new reach adjust knob integrated into the lever is a lot cleaner, I find it impossible to use with gloves on. There just isn’t enough exposed knob to grip, so mid ride adjustments required me to pull a glove off.

My final Shimano brake nitpick isn’t new to this brake, but I’m baffled by the little release button Shimano builds into their levers. Why? It can’t be a safety thing, as you’re not going to make it very far with your unbolted brakes rattling around on your handlebars. I guess it’s sort of easier to start threading the bolt in with the clamp held closed, but the annoyance of releasing the button more than cancels this out. I wish this were simpler.

The caliper itself doesn’t look much different than the old one. Shimano claims an increase in stiffness, which in turn claims increases power late in your brake stroke. A stiffer caliper flexes less and puts more force into the brake pad. I’d have to do some back-to-back tests with the old brake to determine just how much this helps.

Cranks

The new cranks don’t look all that much different from the old cranks, but there are some differences in execution. Most of it is down to simplification. Gone are multiple chainlines and q-factors, with everything now revolving around a 55mm chainline and a 176mm q-factor. If you want a 52mm chainline you can achieve this by using a chainring from the previous generation, which has a 3mm offset (compared to the 0mm offset of the new generation). As well, Shimano has simplified mounting. Gone are all of the crank spindle spacer combinations, and you now just bolt it all together sans spacers. There are still bb spacers, and some washers/shields on the spindle, but it’s now much easier to figure out what goes where during install or re-assembly. Minor stuff, but if you’ve ever sat there staring in confusion at a set of instructions, trying to figure out where each spacer goes, this is welcome.

Wheels

I don’t have much to say about these wheels. Tires went on easy enough and hold air very well. The hubs sound nice. I haven’t hammered on these rims, but they’re still spinning quite true. These seem to be a pretty solid, mid-priced, aluminum wheel. Pete has promised he’s going to dig in further on the hubs at some point, so I’ll leave it there.

In Conclusion

I’m very happy with this stuff. It shifts well and merges many of the best things about electronic systems (fast, easy shifts that you don’t have to think about at all) with the best things about mechanical systems (an intuitive lever that feels just like it always has). Performance wise this stuff is hard to beat. Yes, there are a couple of small things that could be fixed on the next version, and it will be interesting to see if the dual spring system hangs around, but all in all, it works well.

Harder to stomach is the cost and the need to manage batteries. Honestly though, battery life has been a non issue with this system. Maybe SRAM has since fixed this, but keeping a battery charged on the GX Transmission system that I tested was a stressful experience. I don’t have a spare Shimano battery and it never was a problem.

It’s becoming more and more likely that your next bike will have a battery operated derailleur. For a time, this made me sad. Now? Well, now, that thought doesn’t bother me as much. And if I’m not paying for the privilege (or the potential repairs), I’ll take electronics all day.

Shimano XT Di2 M8250