Hayes Dominion A2 brake review

The Dominion A2 from Hayes is a downsized, two-piston version of the A4. It comes with a handful of very useful features that you won't find on competing brakes. They offer a lovely lever feel and plenty of power for general trail riding though they’re prone to fade during prolonged, extra speedy descents and they can squeal a little. Although they're not without a couple of niggles, they could be some of the best mountain bike brakes you can buy.

Hayes Dominion A2 – Technical details

The Dominion takes everything we know and love about the well-received four-piston A4 brake, including the lever, but pares it down into a lightweight package with only two pistons. Hayes says that this brake is ideal for cross-country through to trail riding.

> Buy now: Hayes Dominion A2 Mountain Bike Disc Brake from Chain Reaction Cycles for £114.99

Coming with a very easy-to-use tool-free reach adjust, the Dominion A2 runs on the readily available DOT 5.1 brake fluid, and the lever rolls around a cartridge bearing to offer a super lightweight feel. Handily, the lever uses Flip-Flop orientation - meaning it’s not side-specific.

What's extra cool about the Dominion A2 is that Hayes has designed a number of proprietary features, namely the Crosshair caliper adjustment and the Two-Stroke Dual Port bleed system. Starting off with the former, it’s a simple pair of grub screws found at each of the caliper’s mounts that allow for very precise caliper/rotor alignment.

The latter then serves as a method of achieving an incredibly thorough bleed. On the caliper, there are two bleed ports where you can bleed the caliper independently of the lever.

There are also two sets of pads in the box, as well as olives and such. Hayes claims the brake weighs in at 303g with a 100cm hose and mounting hardware. I weighed the lever at 117g, and the caliper at 138g which overall, is nearly a full 50g lighter than claimed. The Dominion Is also available with a lever designed for little fingers, which is very cool.

Hayes Dominion A2 – Installation and bleeding

Thanks to the Dominion’s unique features, it’s easy to precisely align the caliper and simple to bleed thoroughly, although there is a little more faff involved.

Bleeding the brake is done using the same method as with SRAM’s brakes without the Bleeding Edge tech. Simply fill a couple of syringes with DOT fluid, screw them onto the open bleed ports and compress the syringes alternately until there are no bubbles floating about. However, the Two Stroke Dual Port bleed system adds another step to the process.

Once your traditional bleed is complete and the lever is sealed, you unscrew both ports at the caliper and do the very same method. It’s a bit more work than usual but this makes a very thorough bleed incredibly easy to achieve.

As for the Crosshair mechanism, again it adds a little more work to the installation but it’s time very well spent. Here, you push the caliper with the grub screws wound flush to the inside of the mounts, then you nip up the mounting bolts. Once that’s done, you wind the grub screws in bit by bit to centre the rotor between the brake pads.

It’s much easier and much more accurate than just eyeballing alignment, or squeezing the lever and tightening the bolts but if you wind the grub screws in too much, there’s no going back. You’ll have to start this process again from the start. While I definitely value the ability to bleed the caliper separately, Crosshair is something I don’t want to live without.

Hayes Dominion A2 – Performance

An aspect of the Dominion A2 that I was immediately impressed with was its lever feel. Thanks to that cartridge bearing that the lever rotates around, the lever moves with very little resistance. It’s luxurious and quick to get to the bite point.

Second to the bearing, the shape of the lever is rather nice. It’s not far off from the shape of the lever found on Shimano’s brakes but it's narrower. I can imagine some people not gelling with this shape as it can feel as if it's digging into the finger when hard on the brakes over long distances but it furthers the lever’s overall light feel.

On the subject of the lever, I’m really happy with the tool-free adjuster on this brake. It’s a pleasure to use thanks to its dialled design and certain clicks as it's wound. The Dominion A2 comes with a bite point adjustment too, though I didn’t find this as useful or effective.

The brake’s power is respectable, too. During my usual trail rides, I rarely found myself wanting more. Although, if the trail was particularly steep, or just generally long and demanding on the brakes, I found that they began to fade. This of course made me squeeze harder on the brakes, which introduced a bit of arm pump. This only happened during especially testing tracks that were either particularly fast or required a lot of consistent braking.

A clearer downside is that I found the Dominion A2 to be a little noisy. The noise isn’t anything ear-shattering but more of a light squeal each time the pads met the rotor. I didn’t find this to be a problem but if you like your brakes as silent as possible, the Dominion A2 might not be for you.

Hayes Dominion A2 – Verdict

With a price tag of £180, it’s reaching the mid to upper end of the segment. There are close competitors such as Shimano XT BR-M8100/BL-M8100 and SRAM Level TLM brake. While performance is comparable and maybe a little weightier than others, the features the Dominion packs make it a force to be reckoned with and well worth the asking price.

If you’re looking for a set of brakes that are easy to live with thanks to some unique but almost indispensable features the Hayes Dominion A2 does a cracking job, offering up usable power in a sleek but understated package. Though If your trail riding errs more towards the gravity side, you may find that the Dominion is prone to a bit of fade and generally, they’re a touch noisy but that's where the A4 model steps in.