Review: Shimano BR-MT420 4-Piston Brakes

One could easily make the argument that brakes are one of the most important components on your bike - no matter how fast you're going it's all for naught if you can't slow down. A huge part of that system comes down to setup and maintenance, but the base product has to be functional and reliable to start off with. There's no doubt that the nicest models on the market do an excellent job of modulating speed, but the lower end of the price spectrum is where things really get interesting.


Technical Details

At $135 per end, the Shimano MT420s are about half the price of their 4-piston XT equivalents, and about $50 less than the SRAM G2, which is their closest competition from the other big S. They're seen quite frequently as the OEM spec on many budget builds, which means you can usually find a set of the 420s on the BuySell if you keep an eye out.

Like all the other new-model brakes in Shimano's lineup, these use an inboard perch to keep the lever supported against the bar under hard braking. This gives the lever a stiffer feel, and seems to increase the durability of the clamp in the event of a crash. Unlike other Shimano models, these sport a long "touring style" lever, which differs greatly from the small hooked levers found on their higher-price options.

As you might expect with a budget brake, there are relatively few adjustments that can be made at the lever. You have a tooled reach adjust, and that's about it for on-trail changes. Luckily, you shouldn't need too much more, as the available range of positions is quite large, making these viable for all sizes of hands and reach preferences. As with any brake, you can change the feel pretty significantly with a certain bleed, so at-home mechanics can experiment with that to land on an optimal setup.

The BR-MT420 comes stock with resin pads and resin-only rotors, but luckily you're not stuck with them. Though Shimano refers to these as a resin-only brake, the pads are interchangeable with either the DO3S (resin) or DO2S (sintered) pads, as they both share the same shape. The rotors you typically see paired with the MT420 are the rightly maligned resin-only discs from Shimano - a product that simply need not exist in my eyes. Sure you don't have to bed them in quite as thoroughly, but to what end?

The bleed procedure is the same one-way system as all other Shimano brakes, and proves to be just as reliable when done with care. Some aspect of the simplicity of this brakeset seems to warrant less bleeding than other options, but I'll get to that reliability in the ride impressions.


Performance

There's a fair bit of skepticism about the lowest-price item in any brand's lineup, but in this case that's fully unfounded. Bone-stock, these brakes are good. With a bit of work, they're excellent. Part of what makes them so nice is the simplicity of the lever - these are one of the few brakes Shimano makes that do not use the Servo Wave linkage in the lever assembly, making the pull much more linear than an XT or a Saint.

This results in the lever pull feeling more like a SRAM Code, i.e. longer pull and a more gradual bite ramp up. Compared to a Code, the freestroke is much lighter feeling, letting you feather that bite point a bit more easily.


It's necessary to address the fully-organic elephant in the room: the resin-only rotors and pads. This combo is pretty ubiquitous on a lot of stock builds, mostly because it allows the brakes to have good bite right out of the box without any bedding-in. That said, they do far worse with heat than their semi-metallic or sintered counterparts, and are essentially useless in the wet. Obviously there are myriad compound options out there, but in this case I'm just speaking to the lowest-end Shimano pads and rotors.

In damp and mostly dry conditions, this brake setup does work quite well, offering great bite and a decent run time before things start getting too hot. I do most of my riding in Bellingham, where braking is heavy and sustained, but even on long steep runs I've had the stock resin setup work well enough the whole way down.

Good enough is rarely the goal though, so it's best to modify that stock setup to get the best performance out of the MT420s.

Luckily, this isn't some massive endeavor, and really only consists of replacing the pads and rotors, ideally after you've burned through the ones that come stock. With a solid one-piece steel rotor and some sintered metal pads, these brakes suddenly shine in all conditions, and continue to impress with their reliability.


That reliability is really why I wanted to highlight these brakes. Unlike many of the Shimano brakes I've used over the years, these work the exact same way every single time you pull the lever. No wandering bite point, no weird pump up, no need to flick the lever before that chute to make sure they're still there. I still love my set of XTR BR-M9120s that I've been using for years, but even their consistency isn't quite on par with the MT420s. With regular service and a few setup tricks, I've found ways to make the XTRs work quite consistently, but that level of upkeep can be frustrating when compared with less fussy components.

There is more power on tap with the XTRs (and the lower tiered models in that line), and I do think that hooked lever shape will be more ergonomic for a wider variety of hands, but the Servo Wave linkage is my best guess as to why Shimano brakes are still sometimes inconsistent. Obviously there are tons of theories as to what causes those issues, but in this case the lever difference in the MT420 seems to have cleared them up.



How Do They Compare?

The max power provided by these brakes is pretty close to that of Shimano's other 4-piston stoppers, but like I mentioned earlier, the feel of it is a bit different. This really does come down to the lever, the length of which provides the mechanical advantage in the system, as opposed to the clever linkage used in Servo Wave brakes. Where SLX/XT/XTR models seem to have a full-power point that you're not going to exceed no matter how hard you pull, the MT420s do seem to eke out a bit more as you reef on the lever. Again, the top-end power does seem to be greater in the fancier models, but only slightly so.

For folks who profess to liking more modulation in a brake, this might be the Shimano for you. I'm of the opinion that there isn't a lack of modulation in typical Shimano brakes, just a lack of practice in the riders that say they're too digital. Touchy brakes are a wonderful thing when you're already gripped on the bars, as they can reduce the effort it takes to hold on and squeeze on a brake lever.

Compared to SRAM's G2, I find the power and consistency of the MT420s to be better in all cases. The G2 has a tendency to overheat on longer descents, and loses power under sustained heavy braking. The lever feel between the two is fairly similar, with a linear pull and consistent bite point, but the power on tap with the long-levered Shimanos edges them ahead in my book.

I recently wrote about the Hayes Dominion T2 brakes, and they compare favorably to the MT420s. Overall power goes to Shimano, mostly thanks to the 4-piston caliper and larger pad contact, but I very much prefer the lever feel of the Hayes. That super light action is one of the nicest aspects of the Dominion series in general, and it makes feathering the brakes all the more doable when you're flying down trail. The T2 brakes (or the less expensive A2 counterpart) feel a bit more oriented towards trail riding, where the MT420 can certainly hold its own on harder, faster terrain.


It's worth noting that at the moment you can get a set of Deore MT6100 brakes for a little bit less cash than these, so they're not the all-out cheapest option in the Shimano lineup. That said, I still think there are performance advantages to the MT420 that make it a component worth considering over other lower-cost options. Plus, it has one of the better model names in the Shimano catalog, so that has to count for something.



Pinkbike's Take

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Posted In:
Reviews and Tech Reviews Brakes Shimano Shimano Mt420