First Ride: Shimano’s Back in the Game With New XT and SLX 12-Speed Groups

by | May 30, 2019

Twelve months ago, Shimano announced their 12-speed XTR drivetrain. It looked just as refined and well-executed as you’d expect a top-tier race-oriented group to be, but there was one problem – it was nearly impossible to purchase. Several factors, including a fire at Shimano’s anodizing facility, delayed the production of the group, and the availability kept getting pushed further and further back. In fact, it was only in the last month or so that the entire group, including cranks, became available.

Needless to say, the pressure was on for Shimano to get back on track and regain their footing in the drivetrain market. They’ve responded by releasing new 12-speed XT and SLX groups, and while there may have been struggles in getting XTR to the market, the new components are on their way to retailers at this very moment. The new XT components and will be available to purchase on June 14th, and SLX parts will follow shortly after, which means that Shimano will have three complete 12-speed groups on the market by the middle of July.

There are enough little details about each component to make your head spin, but it’s worth taking a few moments to go over the key features that differentiate the XT from XTR and SLX, starting with the crankset.

XT FC-M8100 Crankset

If the XT M8100 crankarms look familiar, that’s because they’re the same as the model that was used as a temporary solution while the actual XTR cranks were being revised. Shimano had already finished the design work on the these cranks when they ran into production issues with the XTR cranks, so they were initially released with an XTR chainring in order to be able to offer a complete group.

In the XT configuration, the arms are the same, but the direct mount chainring is slightly different – it uses aluminum arms and steel teeth, versus the XTR chainring’s full-aluminum construction. That adds a little weight, but it also means that an XT chainring is roughly half the price of an XTR ring.

There are three chainline options – 52mm, 55, and 56.5mm – in order to have cranks that will fit bikes with 142, 148, or 157mm axle spacing. For riders who pay attention to things like Q-factor (the distance between the outside of the driveside crankarm to the outside of the non-driveside arm), the 52mm chainline cranks have a 172mm Q-factor, which is narrower than what Shimano has offered in the past. If you have a bike with 12x148mm spacing and aren’t sure which option to go with, the 55mm chainline option is the safest bet – that way there shouldn’t be any frame clearance issues, and the 178mm Q-factor is only a couple millimeters different than previous generation XT cranks.

There’s also a double chainring option for the three people out there that are still rocking a front derailleur.

SLX cranks have always been a workhorse option, an affordable and durable choice for riders who aren’t counting every gram, and that sentiment holds true with the new model as well. As Nick Murdick, Shimano’s MTB Product Manager, said, “SLX definitely rides in jeans.”

The SLX cranks have a nice blue tint to them that lets some of the metal grain show through. Honestly, I think they look even better than the finish on the XT cranks. The main difference between the SLX and the XT chainrings is the surface treatment, and the fact the there are only 30, 32, and 34 tooth options – you’ll need to bump up to the XT level to get either a 28 or 36 tooth ring.

Chains and Cassettes

The XT and SLX cassettes are available with either a 10-51 or a 10-45 tooth range, all with 12-speeds. The 10-45 tooth option is aimed at riders and racer who don’t need a super-easy climbing gear and want more even spacing between the gear steps. It also allows for the use of a shorter cage derailleur – which means if you’re willing to give up some gear range you can gain some ground clearance.

The 10-51 tooth cassette, which will be the most commonly seen option, has a 510% gear range thanks to the following gear progression: 10-12-14-16-18-21-24-28-33-39-45-51T. On the 10-45, the progression goes like this: 10-12-14-16-18-21-24-28-32-36-40-45, for a 450% gear range.

The easiest way to tell Shimano’s 12-speed cassettes apart is by counting the number of black anodized cogs. On an XTR cassette the largest three cogs are aluminum, followed by five titanium cogs, and then four steel cogs. XT cassettes get two black aluminum cogs and 10 steel, while SLX has one black aluminum cog and 11 steel.

XTR M9100

The new XT and SLX groups both use Shimano’s Hyperglide+ chain and chainring design.

It’s only possible to take advantage of the full scope of Shimano’s Hyperglide+ technology, which enables shifting under load, by having a Hyperglide+ cassette and chain. Chains from other manufacturers will work, but not as well as going the full Shimano route.

The main difference between the three 12-speed mountain bike chains that Shimano offers has to do with the surface treatment, and whether or not the pins are hollow. An XTR chain the gets highest end finish along with hollow pins, and should be the strongest, lightest, and most durable option. XT and SLX chains are the same weight and strength, but the XT has a different surface treatment that should give it a slightly longer lifespan vs. SLX. According to Nick Murdick, if you were going to only have one XTR part on your bike, choosing the chain is the way to go.

All of the cassettes in the lineup require a Shimano-specific Micro Spline freehub body. At the moment, Shimano, DT Swiss, Industry Nine, and Newmen are the only companies producing compatible freehub bodies, but it sounds like we’ll be seeing more options emerge in the near future.

Shifters and Derailleurs

There are two longer cage derailleur models for both XT and SLX. All of the derailleurs use the same larger pulley design that was first seen on XTR, along with the familiar clutch design. The 8100 and 7100 models are for use with a 1x setup, and the other two options are for the aforementioned front derailleur holdouts. On the topic of front derailleurs, there’s a new all-black option, the first time Shimano has gone with a color other than silver.

There’s also a shorter cage derailleur in each group that’s intended for use with the 10-45 tooth 12-speed cassettes.

The XT shifters look and function nearly identically to their fancier XTR relative, but the release paddle is a little bigger, and the textured rubber pad isn’t replaceable. Both XT and XTR shifters feature Shimano’s two-way release design that allows the release lever to be pushed or pulled to move to a harder gear. You can also quickly drop down two gears with one push of the lever, and each click corresponds to a shift, without any need to let up off of the lever.

The SLX shifter doesn’t get the rubber grippers on the shift paddles, and it also doesn’t have multi-release or instant-release capabilities.

There are two- and four-piston caliper options for XT and SLX.


There was internal debate at Shimano as to whether it was better to offer only a two- or four-piston brake, but in the end the decision was made to continue offering both. There was already an XT-level four-piston brake, but this marks the first time that there’s been a four-piston SLX option.

The brake lever’s shape has been modified slightly from the previous version, with a taller, flatter profile. The lever also has the extra support perch that was originally seen on the new XTR brakes, a feature that makes the lever body more resistant to flexing under heavy braking.

Even the rotors got an upgrade, and the Shimano’s Freeza technology is now available at the XT level. The Freeza Centerlock rotors consist of a layer of aluminum sandwiched between two pieces of stainless steel, with that aluminum layer extending below the braking track to help keep things as cool as possible. The design is almost identical to XTR, except that the XT rotors don’t receive the special heat dissipating paint that those top-of-the-line rotors have.

Wheels & Hubs

When XTR came out, there wasn’t a complete wheel to complement the hubs. According to Shimano, that’s because the wanted racers to have the ability to choose between carbon or aluminum rims rather than locking them into one option. With the XT group, Shimano saw the opportunity to add a tougher wheel than what they’d offered in the past, and the result it the WH-M812. The M812 wheels use offset aluminum rims that have an internal width of 30mm and are laced with 28 J-bend spokes. The rims’ shape combined with the hubs’ wide flange profile allows for a wheel with zero dish, and even spoke tension on both the drive- and non-drive side.

Along with the prebuilt wheelsets, there are also Micro Spline driver-equipped hubs at both the XT and SLX levels. The Centerlock hubs use a cup-and-cone bearing system, and the freehub body has 7-degrees of rotation between engagement points.

Prices & Claimed Weights

Product launches are often held in far-flung locations that require a full day’s worth of travel to get to, followed by a couple days of riding on unfamiliar trails and equipment while battling jet lag. For the launch of XT and SLX, representatives from Shimano made the trip up to my home trails in Bellingham, Washington, which meant that I didn’t need to spend any time in the germ tube, and could focus on the products’ performance without trying to remember what time zone I was in.

The bike I was aboard was the new Ripley, Ibis’ latest version of their classic light and lively trail bike. It was outfitted with the new XT components from tip to tail, with a 10-51 tooth cassette and four-piston brakes.

I’ve been putting the miles in on the XTR 12-speed group in preparation for a long term review, so it didn’t take me any time at all to get used to the feel of the XT drivetrain. Honestly, it’s hard to tell a difference between the two groups out on the trail, and that’s a good thing. I’d say XTR feels ever-so-slightly more smooth and effortless when shifting, where XT’s shifts felt a little more solid, but the difference is barely discernible.

Over the course of two days of riding I didn’t need to adjust the drivetrain at all – each click of the lever was met with a quick, crisp shift. Just like with XTR, the XT drivetrain will happily change gears even when you’re standing up and mashing on the pedals, no matter how counterintuitive that may seem. The shifter’s shape and feel is excellent, and the I-Spec EV mounting system provides a wide range of positioning options. The 51-tooth cog came in handy on a couple of particularly steep climbs, and the jump to that easy gear was nice and smooth – there’s no longer the huge, somewhat awkward jump between the final two gears that was found on the XT 11-speed 11-46 tooth cassette. I don’t usually backpedal more than a quarter turn or so while I’m riding, but I made a few backwards revolutions to see what would happen, and found that the chain stayed right where it was supposed to be.

There wasn’t a whole lot of sustained braking to really put the four-piston brakes to the test, but they did remain consistent the entire time, with plenty of power, especially for the lightweight Ripley. I’m still harboring hopes that Shimano will come out with brakes that have a pad contact adjustment feature, although I have a feeling I’m going to be waiting a long time for that wish to come true.

It takes much more than two days of riding to comment on a new drivetrain’s durability, but I do think it’s safe to say that Shimano are firmly back in the drivetrain game. The prices and weights of the new components are all very competitive, and the shifting performance and feel is top notch – it’s hard to ask for much more than that.