Review | Shimano SLX M7120 4-Piston Disc Brakes Give You Mo' Power, Mo' Modulation

The not-so-minor details


Shimano SLX M7120 Disc Brakes


$460 (pair of brakes, sold without rotors or adapters)


290g (front) & 304g (rear)


- Plenty of brute power on tap
- More modulation than the 2-piston version
- Consistent & reliable performance
- Easy to bleed and maintain
- Decent pad clearance reduces rotor rub


- Finned brake pads still rattle
- Non-serviceable levers and callipers

Wil Tests & Reviews The Shimano SLX M7120 Disc Brakes

Last year Shimano rolled out the brand new SLX M7100 12-speed groupset. Benefitting from trickle-down technology from both XTR M9100 and XT M8100, the latest SLX groupset offers eerily similar on-trail performance, albeit with a few cost-saving manoeuvres to bring the price down significantly. Not long after it was announced, we received a full Shimano SLX M7100 groupset for long-term testing. You may have already read our review of the 1×12 drivetrain, which we pitched against SRAM GX Eagle in the ultimate 12-speed showdown.

shimano slx m7100 1x12 drivetrain groupset disc brakes 4-piston
Shimano launched the new SLX M7100 groupset last year, which includes a 1×12 drivetrain along with new 2-piston and 4-piston brake options.

Of course the SLX brakes are all-new too. And much like the shifty bits, the stoppy bits draw heavily from Shimano’s pricier groupsets. You can get them in 2-piston (M7100) and 4-piston (M7120) varieties, though they both use exactly the same lever. For the past six months, I’ve been testing the 4-piston brakes on both our Trek Fuel EX 9.8 long-term test bike, as well as the 2020 Merida One-Twenty 700 we currently have on for review. Here’s how we’ve got on.

New Lever Design

Up at the lever end, the SLX brakes are all-new and utilise the same mid-mount design as the XT and XTR equivalents. This sees the hinged split-clamp relocated to the middle of the master cylinder, while the end of the lever body actually braces against the handlebar. This is a design we’ve seen before from the likes of German brake brand Trickstuff, and in this case it also helps to increase stiffness when tugging hard on the levers. Combined with the solid bite point, these brakes have a very firm and direct feel at the lever.
The lever blade itself is made from alloy, though it skips the dimpled texturing that you get on XT and XTR. The blade is slightly taller and more blunt than the previous generation SLX levers, which gives your finger a little more to wrap around. The hooked profile is unchanged for anyone who’s familiar with Shimano disc brakes, offering a comfortable perch for single-finger braking.

shimano slx m7120 disc brakes
The lever body is all-new, and mirrors the latest XT and XTR levers.

shimano slx m7120 disc brakes
The lever body braces against the handlebar to stiffen the entire structure when you’re pulling hard on the anchors.

The SLX brake levers also utilise the I-Spec EV mount. This is Shimano’s latest standard for directly mounting a shifter or dropper lever to the brake lever clamp for a cleaner setup. While it’s annoying to have a new standard, I-Spec EV does provide more flexibility with 14mm of lateral of lateral adjustment, and 20° of rotational adjustment via a single 3mm hex key.

Mixing & Matching

The brake levers are still compatible with regular band-clamp shifters and dropper levers though. To begin with, we had our brakes paired up with a regular band-clamp SLX shifter, and Shimano’s MT-800 dropper lever. I’ve also used other dropper post levers, and providing the band clamp isn’t huge, it’ll actually fit into the gap between the brake clamp and where the lever body braces against the bar.
Worth noting is that it’s actually possible to fit a SRAM MatchMaker (MMX) adapter. You just need to remove the I-Spec EV bolt and curved nut, and replace it with the SRAM equivalent. That way you can bolt a SRAM trigger shifter onto your Shimano brakes, and any dropper lever that mounts using the MMX standard. Currently I have a Funn dropper lever mounted that way, and it works a treat.

shimano slx m7120 disc brakes i-spec ev matchmaker mmx clamp
While the I-Spec EV system is designed to fit Shimano’s own dropper lever and shifters, it’s also compatible with the SRAM MatchMaker clamp.

Setting Up

Fitting and setting up Shimano hydraulic disc brakes tends to be a pretty low-fuss affair. The only slight hiccup worth mentioning is if you’re changing over from SRAM brakes and 200mm rotors. Because Shimano still uses 203mm diameter rotors, your existing adapters won’t work – you’ll need Shimano specific adapters to make up that extra 3mm. Otherwise both brands are sticking to the same 160mm and 180mm sizes for their smaller rotors, so adapters are interchangeable for those.
Like the XT & XTR equivalents, the SLX brake levers make use of the Servowave system, which sees a rate-altering linkage in between the lever and the master cylinder. This allows Shimano to build a load of clearance between the pads and the rotor surface, so it’s easier to align the callipers without annoying rub from a slightly-out-of-true rotor.

shimano slx m7120 disc brakes
There’s plenty of pad clearance with Shimano callipers, making them easy to align for rub-free performance.

shimano slx m7120 disc brakes bleed tool mineral oil
Shimano’s cup tool makes for easy bleeding. We’d still recommend doing a full system bleed with the syringe though.

The bleed process is similarly easy. Shimano offers a cheap cup tool for performing quick lever bleeds, and it’s a no-brainer process for even the most mechanically inept. However, I would still always recommend doing a full system bleed to begin with. This involves fitting a syringe to the calliper end, and pumping mineral oil through the lines and up to the lever, where any trapped air bubbles will be ejected out into a reservoir of oil in the cup tool.
The reason I say this is that Shimano brakes are very good at masking a poor factory bleed. Even if they feel solid at the lever, there can still be air trapped inside. On your first long descent where you get a bit of heat into the lines, that air can quickly show up with an inconsistent lever feel. I performed a full system bleed after first installing our SLX test brakes, and they’ve been solid ever since.

More Power, More Modulation

And solid is a good way to describe these brakes. With four pistons chomping down on the rotors, there is plenty of brake force on tap. Compared to the 2-piston SLX brakes, which use 22mm diameter pistons, the 4-piston versions use a pair of 15mm and 17mm diameter ceramic pistons. Shimano claims they are 22% more powerful than the 2-piston stoppers, and I can believe them.

shimano slx m7120 4-piston disc brakes
The SLX M7120 callipers use a pair of 17mm and 15mm diameter ceramic pistons.

The power isn’t immediately apparent though, because it comes deeper into the lever stroke. That’s because the pads engage on a slight angle, with the 17mm pistons pushing out first. Pull the lever further, and the rearward 15mm pistons then push out and engage. The effect is kind of like ‘toeing-in’ a V-brake pad, so you end up with a gradual increase in power, and therefore more early-stroke modulation.
In fact, the modulation with these 4-piston brakes is better than the 2-piston equivalents. If you’ve ever found Shimano brakes to feel a little too digital, with an ‘on/off’ feel, then you need to try the 4-piston versions. They have noticeably better fine-tune control, something that’s apparent on dusty, traction-poor trails where you really want to avoid locking up a tyre. Even with a 203mm rotor up front and a 180mm rotor out back on our Fuel EX test bike, I’ve never felt like the SLX brakes were too grabby. On top of that, they’ve been super consistent with fade-free performance on every trail I’ve ridden.
shimano slx m7120 4-piston disc brakes
The finned pads are designed to improve cooling, though the fins annoyingly rattle against the calliper body. Sort it out please Shimano.

Rattly Brake Pads

Yes, that problem still exists with the Shimano SLX M7120 stoppers. Mirroring our experience with XTR and XT 4-piston brakes, the finned pads have a habit of vibrating against the calliper body, causing an annoying ticking noise whenever you’re riding over choppy terrain. It hasn’t been as bad with our test brakes as with some others, and it is possible to reduce the noise by spreading the pad springs apart. If you still can’t ignore the rattle though, your best bet is to fit non-finned brake pads, which solves the problem.
On that note, there are four different brake pads you can fit into these callipers ranging from $25-55 per end. Ignoring the fancy fins, the actual pad shape and size is the same as the existing Saint and Zee brakes, as well as the newer XTR and XT 4-piston brakes. Here’s what you can run;

shimano slx m7120 4-piston disc brake pads n03c
Shimano offers several varieties of replacement pads for the 4-piston SLX brakes. From $25 non-finned resin pads, to $55 finned metal pads.

If you buy a set of SLX stoppers aftermarket, they’ll come fitted with resin brake pads (N03A – they’re the black pads on the left in the photo above). These are designed to work well in dry conditions. They’re smooth, quiet, and they provide braking power across a wide range of riding speeds, so they’ll suit most Aussie mountain bikers out there. Power does drop off noticeably in the wet though, so if you do ride regularly in all conditions, going to a metallic pad compound may be a better option. The metal pads (N04C) are expensive at $55 per end, but as well as being more durable and better suited to wet conditions, they’ll also hold up better on really long alpine-style descents.
You also get plenty of options for rotors, with both 6-Bolt and Centerlock varieties. I’ve been using XT ‘Freeza’ MT800 rotors, which sell for $89 (180mm) – $105 (203mm). However, there are cheaper non-Ice Tech alternatives available.

How Do They Compare To XT Brakes?

Structurally speaking, the Shimano SLX M7120 brakes are pretty much identical to the XT M8120 equivalent. The XT’s get a sleeker anodised finish, dimples on the lever blades, and they also get the Free Stroke adjuster. Seeing as that adjustment still doesn’t do anything (if you’re listening Shimano, a usable bite-point adjuster would be swell), then you might as well save some $85 and go for a set of SLX brakes instead.

shimano deore xt m8100 brake i-spec ev shifter
The XT brakes get a sleeker finish, along with a dimpled brake lever and the Free Stroke adjuster. Our opinion? Save the cash and get the SLX brakes instead – they perform just as well.

shimano deore xt m8020 brake calliper 203mm rotor
Braking power and modulation is better on the 4-piston callipers compared to Shimano’s 2-piston callipers.

And What About SRAM?

In terms of feel and power, I’d compare the Shimano SLX M7120 brakes to the SRAM Code RSCs. Both have a similarly solid bite point and a tonne of power, certainly more than the G2/Guides. The Codes are about 50g heavier per end, and they feel a touch more powerful than the SLX brakes to me, though unfortunately I don’t have a dyno to hand to verify any numbers. They also have more adjustability via the pad contact dial, which allows you to fine-tune how much dead stroke you have before the pads engage the rotor. Also in SRAM’s favour is the fact that it offers lever and calliper service kits, so you can refresh all the seals and replace the pistons down the line if needed.
In comparison, Shimano doesn’t offer any service kits for its hydraulic disc brakes, though past experience would suggest that they’re capable of going a long time without much attention. I will say that the tool-free lever reach is nicer to use than SRAMs, and I’ve also found the calliper easier to align thanks to the added pad clearance. The new lever body does result in a stronger and more direct feel, which enhances that strong bite point that Shimano is known for.

Flow’s Verdict

As with the rest of the groupset, the Shimano SLX M7120 brakes have proved to be fantastic low-fuss performers. They have great build quality, they’re easy to install and live with, and aside from a few grams, they give up very little to the more expensive XT and XTR stoppers.
The 4-piston callipers deliver greater power than their smaller 2-piston siblings, though it’s the improved modulation that I’ve found to be most noticeable. If you’re choosing between the two, then I would highly recommend you go with the 4-piston brakes – aside from being maybe 30g heavier, they’re better in every way. Along with the new stiffer lever body and improved adjustability via the I-Spec EV system, this is one superbly versatile and reliable set of disc brakes.

Mo’ Flow Please!

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