12-Speed Shimano XT Review: Lessons After 2,500 Miles
We got Shimano’s full 12-speed M8100 series drivetrain and new braking system shortly after its release back in 2019. Following about 2,500 miles of use, here’s our atypical Shimano XT review, which sheds light on 10 things we’ve learned about it and compares it to SRAM Eagle and SLX…
In a big announcement back in spring 2019, Shimano launched their completely revamped DEORE XT and SLX groupsets, adding an extra gear, one-upping SRAM by a cassette cog tooth, and trickling down much of the 12-speed tech that was formerly reserved for the pricey XTR group. This not only put 12-speed Shimano at more affordable price points, but it also shored up the foundation for their new Microspline freehub standard and gave them a full range of 1×12 drivetrains. We got both the Shimano DEORE XT M8100 and the SLX M7100 groups to test and have been racking up the miles on both ever since.
The world has changed a lot since 2019, and there have probably been five dozen Shimano XT reviews published since then, so I’m going to do this one a little differently. Instead of a conventional review with 500 words on how it’s constructed and another 500 on how it performs, and so on, I’m going to skip all the details that most of you already know or could find elsewhere and approach it from a perspective of things I learned about this group. Along the way, I’ll compare it to SRAM Eagle GX and X01, as well as the Shimano SLX group.
So, without further ado, here are 10 things I learned during and after putting over 2,500 miles (~4,000 kilometers) on the Shimano Deore XT M8100 group. For the record, I’m not entirely sure on the 2,500-mile number for this review—I’m not a meticulous number-keeper—but that estimate is conservative, and I’d say I have more on it than that if anything.
Shimano 12-speed Gearing is Better for Mountain Biking
It’s refreshing to not really have to worry about having enough of a granny gear with modern 12-speed drivetrains. Obviously, there are sometimes nuances with how much gear you’re carrying, what the terrain you’re riding is like, and your personal riding style and strength. But since Shimano and SRAM have upped their game with the addition of 51 and 52-tooth cassette cogs, respectfully, you don’t have to be too concerned with having a proper low gear, even when riding a loaded bike. And with 10 teeth on the high-end, both the Eagle and Shimano systems have a plenty adequate range for bikepacking, trail riding, ATBing, or gravel, for that matter—in my opinion. However, they’re both wildly different when it comes to their gearing progression.
Shimano XT: 10-12-14-16-18-21-24-28-33-39-45-51T
SRAM Eagle: 10-12-14-16-18-21-24-28-32-36-42-52T
As you can see, SRAM maintains tighter ratios throughout the middle-top end of the cassette before jumping 10T in one massive final shift to the 52T cog. By comparison, Shimano’s 12-speed cassettes start to open up at the ninth gear and make bigger steps between the 28 and 39 tooth sprockets. There’s definitely a noticeable difference between the two. In my experience, Shimano’s approach makes the transition into the largest 51 tooth cog feel more fluid and seem more integrated into the usable low range. The SRAM method is more of an emergency bailout gear approach. On the trail, SRAM’s translates to friendlier mid-gear spacing for flatter or rolling terrain or trails, or gravel rides and mixed-terrain riding. Shimano’s, on the other hand, offers more closely spaced low gearing that I find to be far superior on steep terrain with hard climbs where the final three ratios are smoother and easier to shift between. I won’t state that one is better than the other overall, but I think Shimano’s gearing ratio is far more friendly for mountain biking or touring and bikepacking on steeper mountain terrain.
It’s worth talking about chainring size a little bit here. Most mountain bikes come stock with 32T chainring these days, which I’ve always found makes a great pairing with a 10T cassette cog for a high gear on a 29er mountain bike. It’s not nearly as high as the gearing on a gravel bike, but it’s high enough to avoid spinning out while trail riding, mixed-terrain riding, or loaded bikepacking. However, even considering the generous granny gear provided by the larger 51 and 52-tooth cassette cogs, a 32T chainring can often seem a little off when riding ultra-steep roads and trails, particularly when loaded. Not so much for the granny gear, but in the top three or four cogs. This is evident more so in SRAM’s Eagle when mountain biking on steep terrain. Shimano’s gear ratio solves this for most riding conditions. However, I still find a 30T ring as a better choice in the mountains or when loaded bikepacking is involved.
Shimano XT is Easier to Set up and Dial In
Truth be told, I’m not the best mechanic when it comes to drivetrains. Despite the fact that I do bikes for a living and am always rebuilding and tinkering as part of my job, I’ve never been great at tuning a tricky drivetrain. I have good days setting them up, and other times calamities ensue. I nearly threw Virginia’s Deadwood off a mountain in the Republic of Georgia once because I couldn’t get her Eagle GX derailleur to shift properly. On other occasions, I have flawless success and suddenly think I should become a pro bike mechanic.
I’ve found that the most difficult drivetrain to tune is the aforementioned SRAM Eagle GX. It drives me crazy, to be honest. Not only do you need the B-gap alignment gauge, but the rear derailleur is also super finicky when it comes to cable tension and derailleur hanger alignment. On the other hand, the easiest to tune is SRAM Eagle GX AXS, oddly enough. And the easiest mechanical drivetrain I’ve tuned is Shimano XT.
One excellent design decision Shimano made that contributes to the ease of set up is a B-gap alignment gauge built into the derailleur (see photo above). You simply shine your phone light down there and adjust the B-tension screw until the teeth line up with the mark and you’re done. I also feel like the XT derailleur isn’t nearly as sensitive to cable tension. I’ve set up a couple of Shimano 12-speed drivetrains and tuned a couple of others for review bikes. All were super easy to adjust to a state where they shifted crisply and accurately. I’ve found XT and XTR to be a little easier to tune than SLX, for what it’s worth.
Stays in Tune
It’s hard to say what makes some drivetrains remain in tune longer than others. I’ve had mixed results with SRAM Eagle. A couple of the systems—both GX and X01 mechanical—have stayed in tune for a while, and others fell out of tune and never seemed the same since. This XT drivetrain has pretty much remained in tune since day one, barring a couple of tweaks of the barrel adjuster here and there. I’ve had a couple of other 12-speed Shimano drivetrains on review bikes and had the same experience.
The Chain is Very Durable
After putting the first 1,000 miles on this drivetrain, I was discussing it with a friend and debating whether to replace the chain. I hadn’t checked it yet, but based on mileage, I figured it was probably close to its end. I ultimately decided to not check it, let it ride, and just keep racking up the miles to see how it fared. This is a test, after all.
When I finally checked the chain wear last week, I was surprised to see the Park Tool CC-2 Chain Checker showed it at about 60% wear—displayed as 0.6 on the gauge, which represents 0.6 of one percent elongation between links. Technically, that’s not enough to warrant replacing it, as 0.75 is the magic number. But, 2,500 miles on a single chain is quite impressive, and I’m guessing at that rate, 3,250 or 3,500 would be attainable before it hit the dreaded 0.75. UPDATE: based on a couple readers questioning the accuracy of the Park Tool CC-2, I measured the chain with the CC-4. It didn’t drop below the 0.5 notch with this tool. After double-checking the Park Tool instruction video for the CC-4, when I apply full pressure on the segment of chain between the hook and tension tip, the gauge tip doesn’t drop into the link without really forcing it. So, if it’s accurate, this chain is below 50% wear.
The Cassette is Durable Too
At first, I had my doubts about the XT cassette. It required the new MicroSline freehub standard and didn’t have an elegant one-piece design like the Eagle GX and X01 options. Instead, the CS-M8100 features a nine-piece design with a single main cluster containing the seven lowest gears (largest cogs) pinned to a forged spider. The five highest gears come as separate sprockets that are installed onto the hub with two spacers and a threaded end cap. The largest two sprockets are made from aluminum to help reduce weight.
Still, no other mechanical drivetrain shifts as smoothly, in my opinion. This is owed to the fairly sophisticated shift ramps on the cassette, or what Shimano dubbed as Hyperglide+ technology. When paired with the HG+ chain, the XT drivetrain shifts quickly and easily in both directions, even under load. One might expect these intricacies to translate into less durability. However, as you can see in these two recent photos, there’s still some life in this cassette. It’s worn, but not as much as you might expect at this mileage.
Surprise, It Shifts Under Load
Smooth, precise shifting is great and all, but one of the most interesting benefits to this drivetrain is the ability to shift under load. I’m used to not shifting under load, to the point where it’s automatic: let up, shift, then push the pedals. It’s second nature, almost like driving a stick-shift car. Somewhere during the middle of my testing period, Neil mentioned, “The shifting under load blew me away!” Honestly, it wasn’t until that point that I really tried it. Lo and behold, it’s quite impressive. Simply put, you can downshift or upshift with a fair amount of pedal pressure and it just pops into place. There’s a little bit of noise, as to be expected, but nothing compared to other drivetrains.
Easier on the Hands and Wrists
First off, aside from the 12-speed XTR I had on a demo bike, this is the best feeling mechanical shifter I’ve tried from any brand. The ergonomics are great, and indexing has a nice firm click with a smooth lever action that has a very consistent feel throughout the entire range, meaning it doesn’t ramp up more tension when shifting in lower gears, which is often the case. It also offers multi-release shifting in both directions, so you can go down two gears at a time and shift into harder gears two at a time, which is a unique feature that I’ve come to really like.
For all those reasons, I’d heard that Shimano was the better option for folks with carpal tunnel or wrist issues. In terms of mechanical drivetrains, using XT confirmed that. I think AXS is probably the best choice for those with serious hand or wrist issues, however. For the record, Virginia has ongoing wrist gremlins and had carpal tunnel surgery in her right hand a couple of years ago. We put AXS on her touring bike (the Wayward) for that very reason, and Shimano SLX on her trail bike. Both are working well in that regard.
Shimano Clutches Need Regular Maintenance
Shimano’s adjustable derailleur clutch is the heart of the derailleur and part of why it performs so well. It keeps the chain from falling off, eliminates chain contact with the chainstay (aka chain slap) better than most derailleurs, can be disabled for wheel removal, and is adjustable via a 2.5mm hex key. It works great until it doesn’t. In short, unlike SRAM’s internal static clutch, its adjustability means that it’s not completely sealed from the elements and needs regular maintenance, particularly in wet environments from what I can tell. At somewhere around 800 miles into this drivetrain, I noticed that the derailleur was sticking and locking in a down position. This caused the chain to have extra slack and basically flop around. It was fixable on the trail by simply disengaging the clutch with the switch on the derailleur body, but that meant chain slap was back, and the risk of dropping the chain.
Some Googling turned up a few tutorials on how to clean and grease your clutch, as well as evidence that this was a common occurrence at this mileage. I won’t get into how to perform this maintenance since Neil just made a video on the subject for the same reason (see below). I will add that it wasn’t too difficult, and it’s probably something that could be done on the road if you carry a little of the special grease. Additionally, I also heard that Shimano fixed a seal issue in later iterations of this derailleur, although I haven’t been able to confirm. One more random thing to add is that there’s no lockout on the Shimano derailleur, which is a little frustrating when compared to Eagle.
How to Service a 12-speed Shimano Derailleur Clutch
Most modern rear derailleurs have a built-in clutch mechanism that helps keep the chain tightly wrapped while bouncing over rough terrain. Some are simpler than others, but the more intricate and adjustable Shimano clutch sometimes sticks after a lot of use and requires regular maintenance. In this video, Neil walks through how to service a Shimano 12-speed XT derailleur clutch and why it should be done every few hundred miles:
There are Compatibility Issues
Shimano’s 12-speed chains are optimized for use with Hyperglide+ cassettes using a construction Shimano calls Dynamic Chain Engagement+. From what I understand, this places a priority on downshifting and has a smaller inner width than normal. As a result, the chain isn’t really compatible with other drivetrains as it can get stuck along the chairing. There are exceptions, and many third-party companies are making HG+ compatible chainrings now, such as Wolf Tooth and Race Face. Theoretically, you can use another 12-speed chain with a Shimano HG+ cassette and chainring. However, you probably won’t get the same level of shifting and chain control as you would with a full Shimano setup.
XT Brakes are More Reliable Than SLX/Deore
A few of us here have had an excellent experience with the latest generation of Shimano XT brakes. They have strong stopping power and improved modulation over the previous generation. The lever feel is great, too. They feel ergonomically perfect and adjustable, allowing one-finger braking in pretty much any given situation. For hydros, they’re also a cinch to bleed, as long as you have the Shimano bleed funnel. One downside is that they don’t work particularly well in cold conditions.
The XTs have proven to be very reliable as well. Three of us here have thousands of miles on them with zero issues to speak of. A couple of us have experienced good long-term results with SLX 4-piston model, too, although Virginia recently had a little trouble with them losing power on multiple occasions. Talking to a few mechanics, this isn’t all that uncommon. In addition, a set of newer 4-piston Deores we tested developed leaky calipers after a year of semi-regular use. I’d say that it’s worth the extra money to spring for the XTs.
- Crisp, smooth shifting that’s easy to setup and tune
- Stays in tune… set it and forget it
- Perhaps one of the most durable derailleur-based 1x drivetrains on the market
- Ergonomics and consistent index tension are easy on the hands
- Chain and chainring compatibility can be a concern, particularly if you’re trying to source parts on the go
- Clutch maintenance might not be for everyone
- Parts have been tough to come by in the current supply chain
- No lockout on the derailleur (like Eagle)
When I first tried the 12-speed XTR group that was specced on the demo Ibis Ripley I tested back in 2018-19, it was clear that Shimano figured out the special sauce for mechanical 1×12. All I could hope was that the same qualities would trickle down to the more attainable XT group. Several months later, after my first ride on XT, I wasn’t disappointed. It shifted with an unflappable crispness, had the same best-in-class ergonomics and ease, and the four-piston brakes were powerful and perfect, even with one finger. Even better, after putting in a lot of time and miles on the XT group, I can now vouch for its durability and reliability too. Obviously, the derailleur clutch requires some maintenance and has its limits, but I don’t think that’s a game changer. It’s easily serviceable, at least.
I would still venture to say that the Shimano XT group is my personal favorite overall for mountain biking applications. And with the excellent level of durability, closer low gearing priority on the cassette, and hand-friendly shifter, brakes, and derailleur, I think it’s a great performer for bikepacking too. It just may require a little forethought on longer trips.
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