Long-Term Test: Shimano SLX M7100
16 months on the workhorse group
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As we’ve written quite a few times in many places, bikes (and all the things we bolt onto them) have gotten really, really good. It’s hard to buy a bad bike. That’s in part due to better frame design, but is also immensely helped by component improvements. The base-level budget builds are perfectly fine for real-world trail use, and the middle-level options perform better than the top-of-the-line stuff from a few years back. Shimano’s SLX M7100 group is a bit of a standout in this department—but that’s really no surprise. Back when Shimano had yet to release its 12-speed groups, some riders were asking for a 12-speed SLX option before they were asking for XTR. Why? Because for most intents and purposes, there’s no reason to shell out the cash for XTR when you have a system as good as SLX has historically been.
I guess that was a bit of a spoiler. Now you don’t have to read this review. But wait! There’s certainly more to this story to tell. I’ve spent 16 months on the same SLX M7100 groupset (brakes and drivetrain) in an effort to provide a real-world, ride-it-til-it-dies Beatdown review. Here’s another spoiler, SLX didn’t die.
Before we really dive in, I’ll give some background first, namely as to what I’ve also been riding at the same time as this long-term SLX test. I have, either on a test rig or my personal whip, this SLX test drivetrain, a SRAM Eagle GX drivetrain, SRAM GX 11-speed drivetrain and SLX 11-speed drivetrain. Brake options include the SLX M7100 brakes, Shimano M810 Saint, Shimano BR-M520 Deore-level brakes, Magura MT4 and finally SRAM Code R. As you might notice, most of my preferences in components rest in the work-horse range, those offerings that are focused on getting the job done, but don’t have the thrills and frills of the upper-level stuff.
Why is this pertinent to a review on SLX M7100? In short, price and place. The SLX M7100 group mostly sells itself by its comparison to other groups—it’s the “better” in the “good, better, betterer, best” lineup that Shimano (and SRAM, for that matter) offers. It doesn’t exist in a vacuum, and in many ways, SLX is best described by its place in the MTB industry component hierarchy.
But enough rambling.
Here’s what’s been on test: BL-M7100 levers mated to BR-M7120 calipers (four-pot), CN-M7100 chain, CS-M7100-12 10-51t cassette, RD-M7100-SGS rear derailleur, SL-M7100-IR rear shifter w/I-Spec mounting, and FC-M7100-1 crankset.
SLX M7100 Braking Performance:
To get right down to it, the new SLX brakes would be my favorite brake on the market—if they didn’t still suffer from the wandering bite point that plagues Shimano brakes. But with a fresh bleed, slightly overbled in fact, the SLX brakes offer a classic Shimano snappy feel with a bit of SRAM damping thrown in to lessen the classic “on/off” feel of stronger Shimano stoppers.
That’s probably the first thing one notices about the SLX brakes, actually. Initially, the lever feel is very, very similar to the older four-piston Shimano brakes, complete with a hard initial bite that doesn’t leave you guessing where things are engaging. That first part of the lever pull might feel similar to older Shimano brakes, but the meat of the squeeze is where things really get shaken up. When you yank on the anchors, the brake pressure ramps up quickly, then slows down significantly near the end of the lever throw. Like a logarithmic curve, the rate at which brake pressure (master cylinder pressure, actually) increases quickly initially, then falls off. Why? Modulation!
Well, it’s to aid modulation, as modulation is something your finger, not the brake, does. SRAM is most attributed to having “better modulation” than Shimano brakes because, historically, SRAM brakes fall off more quickly whereas Shimano brakes have a more linear feel. In other words, when you keep pulling Shimano brakes, they just try to stop you more, whereas SRAM brakes are like, “Are you really sure you want to do that? ‘Cause, you know, you might skid or something.”
To be clear, the SLX 4-pot brakes are powerhouses. If you want to lock things up, you can. Want to Euro nose pivot around a switchback? No problem. The absolute power isn’t really what I’m talking about here, rather how the brake achieves that power. I’ll also note that I tested these brakes with the D02S metallic, finned pads.
The new SLX brakes split the difference between the SRAM and classic Shimano approach, staying true to Shimano’s usual feel, but edging it closer to a more conservative end-lever feel. When you really want to lock up a wheel, you certainly can, but it’ll take slightly more lever pressure than something like the BR-M810 Saint. However, that’s not a bad thing (like SRAM fans have touted for years). The most effective braking happens at the point just before lockup, which is where the SLX brake really wants to be. There’s a pretty sizable range from “brake on” to “brake locked” where your finger can live and poke about. Panic braking no longer immediately results in skids, and I’ve found it’s easier to inch down steep pitches or rock faces without braking traction—the line at the edge of traction can fit more than just a toe.
This is also really aided by the movement of the clamp to the mid-point of the lever to act like a brace, as well as a clamp. This puts the end of the lever right against the bar, increasing stiffness to the lever feel. In practice, this makes things feel more crisp and responsive, as well as aiding in maintaining that just-before-washout traction zone.
At least until the bite point wanders and the lever pulls almost all the way to the bar. I won’t be coy here, I’ve taken the SLX brakes off my personal rig and replaced them with my old Saints as I’m better able to set up those brakes—which also suffer from bite point issues—to mitigate wandering-lever syndrome. I run my levers close to the bar, and there were a couple of times when I thought I’d lost brake pressure as the lever simply went right to the grip on the first pull. To be fair to Shimano, I’ve heard very mixed reports as to the consistency and degree of bite point wander on the new brakes (SLX, XT and XTR). I may have just gotten an off set of brakes, but regardless I found that I needed to do a fresh over-bleed on my test set at least monthly in order to keep them consistent. That’s too often for me.
I should also mention that the finned pads that come with the four-pot SLX brakes still rattle like there’s no tomorrow. I personally mitigate this by using 3M mastic tape between the fin and the brake caliper, but that is certainly not Shimano approved. The old-style, finless pads still work just fine, and like the old XT and Saint four-piston caliper (they were the same thing), heat build-up doesn’t really become an issue with large rotors. With 180mm and smaller rotors, finned pads really do make a difference.
Additional SLX M7100 brake thoughts:
This generation of SLX brake is the first to come with a four-piston version, and sports near identical adjustment features as the XT and XTR options. You lose the bite-point adjustment (which, contrary to popular belief does actually do something, although I never missed it on the SLX brake) but you still have tool-free reach adjustment, a classic Shimano bleeding system and a Banjo connection at the caliper. It should be noted that the Banjo uses different hardware than the older Shimano brakes, although the BH90 hoses remain the same (I’ve tested this).
A small annoyance with the SLX caliper is that some 5mm Allen wrenches won’t fit into the lower or “rear” caliper bolt, especially if you use a bit-driver-based system. A plain 5mm piece of steel will fit fine, but tools like the Park T-handle won’t and you will strip the bolt head using a rounded Allen key. The fit isn’t as tight as the SRAM Code, so most multi-tools will still make it in there. Just bigger shop tools might have issues.
Finally, the SLX brake’s inboard lever clamp will play nice with most SRAM and Shimano shifters and bar-clamping bits, but it definitely works best with Shimano’s I-Spec EV system. I found the range of adjustment adequate to get the shifter inboard enough (something I struggle with on other systems), and Shimano even makes an excellent 1x dropper lever to go with the system. The one downside to the I-Spec EV system is that not every company makes that mount for their product (especially dropper levers) and third-party solutions add to the cost, or aren’t available at all (yet).
Let’s Switch Gears
The other elephant in this room is the, well, rest of the SLX group—specifically the qualitative function of the new Hyperglide+ bits and bobs.
In a nutshell, no other drivetrain shifts like the new Shimano 12-speed stuff does. You’ve probably already read, like, five other reviews that have said the same thing. However, what I’m about to write you probably haven’t already read and is also probably a bit controversial.
Personally, I don’t actually get along as well with Hyperglide+ as it seems everyone else does. There are a few aspects to this, and I’ll lay them out in detail.
I learned to shift on non-indexed bar-end shifters. This required precise timing in both shift, cadence and drivetrain load, all of which are bundled together in a set of skills that have been beneficial for use with every other drivetrain (OK, chain-driven, you gearbox fans) since those old days. However, Hyperglide+ doesn’t respond to that style of shifting in the same way. In fact, the system almost favors what I’ve always known to be bad shifting practices.
In other systems, one must slightly unload the drivetrain while shifting—if you don’t do that you run the risk of popping outer plates off pins or bending links (hello, e-bikes). On Hyperglide+, it actually seems to favor shifts performed under a decent amount of drivetrain load. If you unload the drivetrain, like you normally would, the shifts are not as crisp, especially upshifting. This runs counterintuitive to how I’ve ridden a bike for the last 20-some years and even after 16 months on this drivetrain (along with other test bikes that have had Shimano 12-speed), I’m still getting used to it.
And then, when I switch back to a SRAM or any 11-speed system, for a while my shifting sounds like bad percussion in a shooting gallery. In effect, I’ve been unlearning one way of shifting in favor of another. Of course, most modern drivetrains can stand up to a fair bit of shifting abuse (as evidenced by my own experience and those I’ve seen during my years of working in shops), but dang, it pains me still.
With all that said, I’ll be clear in that this is all my experience and opinion—I haven’t heard these thoughts repeated anywhere else. This is surprising, but I’ve had more than enough time and experience with this system to justify my posits.
True to its intention, Hyperglide+ shifts incredibly smooth under load and offers that performance advantage over any other drivetrain out there. However, if you’re used to older-style shifting practices, Hyperglide+ might require metacognitive adjustments.
On setup and adjustment
This will be a brief section, but important. Shimano 12 speed systems rely on proper derailleur setup, specifically the B-limit. There’s a tiny gauge on the back of the cage (so you don’t have to use or buy another tool) that you line up with the largest cog when shifted into the said cog. The process is fairly easy to do, although the gauge is pretty teeny-tiny.
Additionally, and thankfully, the Shimano system seems very resistant to cable/housing wear. I’ve only changed my lines once (well, cable four times due to other circumstances) since I’ve installed the system, and I only began to notice major shifting issues about eight months into testing. On the other 12-speed drivetrains, I get a few months in bad weather before cable/house wear starts to degrade performance in the upper half of the gear range. I always use Shimano SP41 (cause it’s the best) housing—using other third-party housing is a bad idea if you want consistent performance.
Let’s briefly talk about doing things that Shimano says not to:
You can technically run non-Hyperglide+ chains on Hyperglide+ cassettes. In fact, I’m doing it right now with a SRAM GX Eagle chain, derailleur, etc and the system shifts just as well as the old GX Eagle 10-52 cassette did, only without the weirdly big jump between the biggest two cogs.
While you can mix and match, Hyperglide+ only lives up to its potential with a Hyperglide+ chain, which uses special little outer plates to “pull” and “hold” itself between cogs while shifting. Where other chains and systems will fall or jump between cogs when under load. The Hyperglide+ chain clings and climbs around like freakin’ Spider Pig, all smooth and stealthy with no loud bangs or pops.
That being said, it totally works to run non-Shimano chains (and derailleurs) with Shimano cassette. Why do I mention this? Because we live in a real world, one defined by a pandemic and supply shortages. Can’t get a Shimano chain? Well, you can run something else and the system won’t totally fail, even if it’s not ideal.
Notes on durability:
I’m seriously impressed by the new Shimano stuff. While I have been swapping around parts (I have an XT/Deore group as well that I’ve been mixing and matching in with SLX to get a feel for the differences), I have yet to fully wear out a cassette to the point where it needs replacing. That’s 16 months of use (admittedly some of that time recovering from injury). The chainring is starting to show some wear, but after swapping it out for a new one just before writing this review, what little chain suck was initially present on the fresh ring/old chain combo disappeared after the first wet ride.
On the note of weather, I haven’t noticed any change in performance based on conditions, outside of what you might expect from a drivetrain covered in mud versus one fresh and clean. Of course, a clean and properly lubed drivetrain makes a big difference, but the tight 12-speed gear packing doesn’t get over-clogged or anything of the sorts.
As far as the derailleur is concerned, I have a few additional thoughts on durability. For starters, the SLX mech uses bushings in the pulley wheels instead of bearings like XT and XTR use. They’re greased from the factory, but in wet weather I have to pull and lube those every few months or else they start squeaking (the latter happens in deep summer dust too). Deal-breaker? Definitely not, but it is more maintenance at the trade-off of cash money.
To the SLX derailleur’s credit, the thing can shrug off hits like a total champ. I’ve actually completely pretzeled the cage twice, both times I was able to straighten the cage out trailside and finish the ride without making any cable tension adjustments. That’s pretty incredible. Granted, it’s not great that the cage twisted up in the first place, but then again I doubt any derailleur could have stood up to the rocks I hit (totally intentional of course. For testing purposes).
I should also note that I snapped the clutch (stabilizer) lever off the derailleur partway through the test. I’ve never done that before, and no other part of the derailleur was damaged, but it’s something that can happen. The stabilizer works fine still, but releasing it to take the wheel off now requires pliers or a screwdriver.
On the shifter
The new SLX shifter is good. Just good. It fits well with the I-SPEC EV mount and new SLX brakes, the ergonomics are pretty much the same as typical Shimano shifters, it’s pretty cheap to replace and changing a cable still just takes a screwdriver to get the little plug out (which somehow, I’ve never lost).
But to recap, it’s just good. Not great. My biggest complaint is that it lacks the double upshift that XT and XTR have—and you can’t help but wonder if Shimano only holds that back to make you upgrade. The price difference between SLX and XT shifters is also quite small, $21, and if there was one part of this drivetrain I’d immediately swap out (and has since done so on my personal ride), it would be the shifter.
That all being said, the SLX shifter is still a good shifter. It, as with the rest of Shimano 12-speed, boasts an increase in shifting leverage, meaning that the downshifts are actually easier and quicker than on 11 speed. They’re also a bit quicker and easier (as in how hard it is to push the paddle) than 12-speed SRAM shifters. However, the SRAM shifter does feel more snappy and solid in its shifts, whereas the Shimano (both SLX and XT) feel a bit muddy by comparison.
What about those cranks?
Cranks are cranks. Depending on how you think about it, they’re probably the least interactive component in your drivetrain, even though you’re constantly turning them. They are the definition of a workhorse component, which happens to be what SLX is good at. They look slick, but plain, with a utilitarian design and features we’ve been seeing on Shimano cranks for many generations. They still use the pinch-bolt design, which works well but requires two tools (including one specialty tool that, thankfully, can easily be improvised) to take off. However, the cranks are much easier to remove, as far as the strength needed, to take off—SRAM cranks are why I still have a cheater bar in my garage.
Installation of the SLX cranks feels refined and smooth. There are no dust caps that fall off the bottom bracket when you slide the spindle through, and the whole crankarm slides on smoothly without having to also thread in a bolt at the same time (again, I’m comparing these to the most popular alternate option).
However, the direct-mount chainring requires a specific tool (oh yes, it’s another standard), and finding aftermarket chainrings is surprisingly difficult right now. You can not run a Shimano Hyperglide+ chain on a non-Hyperglide+ chainring because of Shimano’s unique inner-plate widths and shapes, which makes finding chainring options for non-Shimano cranks difficult, though Wolf Tooth has a few that we particularly like.
Where does SLX stand in Shimano’s lineup?
I’ve already noted that using the XT shifter instead of the SLX shifter would be a solid investment if you want that double upshift (which you do). Let’s keep exploring these thoughts though, as I mentioned in the beginning, SLX is defined by its brethren.
As for the rest of the drivetrain, I would recommend an XT or XTR chain over the SLX option. The higher-end chains offer more strength and wear-resistance (due to coatings and hollow pins), also at a pretty small price difference ($11 more for XT). The cassette is where you’ll save the most weight by upgrading, but also where you can dump the most cash. You won’t get any shifting advantages though, so I’d stick to SLX unless you’ve got the spare cash.
In a perfect world, I’d run an XT shifter, XTR chain, SLX cassette (to save some weight) and Deore everything else, as my experience with Deore derailleurs has been favorable. However, that’s more of an aftermarket/custom build, and SLX mostly comes on full builds—in that light, if your bike came with SLX, don’t worry about changing things out (except maybe that shifter).
As for the brakes, unless you really want fancy carbon or a bite-point adjuster, there’s no reason to go above SLX. Deore 4-piston is a bit of a downgrade, lacking a tool-free reach adjustment, and are often (but not necessarily) specced with lower-end rotors. SLX brakes run $180 per wheel, which is very reasonable for what you get.
I, the reviewer, do render my judgment here. In short, SLX is not without its flaws, but its benefits far outweigh them. And holy heck, you get so much more than your money’s worth. In fact, Shimano may have given the people too much of what they asked as it’s hard to justify going with either of the most expensive alternatives over SLX—it’s that good. True, you miss out on some neat features and certainly some weight savings (upwards of 400g between SLX and XTR), but you have to ask yourself, “Do I really need that?”
Shimano may have a habit of being a bit slow out of the gate and dragging its feet in adopting new standards, however, it also has a habit of absolutely knocking things out of the park when it finally does reveal products to the world. If we’re going to be stuck with the current version of SLX for as long as we were stuck with the last version, well, I don’t think we have anything to worry about. In fact, we have everything to look forward to.