Hayes Dominion A4 Brakeset Review

Hayes Dominion A4 Review

Words & Photos by Rob Dunnet

There was a time in mountain bike history when Hayes was at the leading edge of hydraulic mountain bike brakes. The Hayes Mag brakes were arguably the best hydraulic brakes on the market, and it was hard to imagine Hayes making a brake that didn’t work well. Then in the late 2000’s Hayes started making products that were less than well received by the mountain bike community and there is an entire generation of riders who have not only never ridden Hayes brakes, but they’ve probably never even heard of Hayes.

Fast forward over two decades later and Hayes has a new brake that they are marketing as the return to their old ways. Can the Hayes Dominion A4 bring the brand back to its former glory? It’s going to take a lot more work than just producing a good brake, but since we’re reviewers and not marketing or advertising experts, let’s just see how they perform.

Hayes Dominion A4 Brakeset Review


The Hayes Dominion A4 brakes are designed from the ground up. Hayes looked at what worked for them in the past and more importantly, what didn’t work. From there they dug their heals in and started from scratch. Everything from pistons, leverage rates, to rotors and pad materials. Instead of pushing the Dominion through development and into production they took their time and made sure they got it right.

The Dominion A4 master cylinder features Hayes’ Dead Stroke. Each master cylinder is set at the factory to have the lowest possible dead stroke, which is really impressive. This is done by aligning the reservoir return port right at the end of the cup seal at the end of the piston. Their goal is to ensure consistent engagement and a crisp bite point. Pad contact can be adjusted by a small screw under the lever blade.

Hayes Dominion A4 Brakeset Review

Something that Hayes discovered in their research is that modern day riders don’t like to pull levers nearly as hard their forefathers. Turns out our fingers have gotten weaker over time and we expect speed-scrubbing power at the tip of one finger. Gone are the days of hamfisted two-finger grabbers. To reduce friction and increase efficiency Hayes now uses ball bearings at the pivot point for a smooth lever feel. The master cylinder pistons are made from aluminum instead of plastic to avoid any deformation or swelling with changes in pressure or temperature. Hayes also utilized a glide ring on their pistons to reduce any friction and provide a consistent light lever feel when applying pressure.

Caliper construction on the Hayes Dominion A4 utilizes a two piece aluminum body and four pistons to grip onto their D-Series Rotor. The caliper also features Hayes’ two port bleeding system that they call Two-Stroke. Hayes claims that having a bleed port on both sides of the caliper allows more air bubble to be removed easier. The pistons in the Dominion A4 are also unique to Hayes. The caliper bore is very tight to the piston in front of the seal, but behind the seal the bore is larger. This allows the piston to be able to rotate within the bore. Allowing the piston to rotate in the caliper allows for consistent pad pressure against the rotor and limits brake fade and uneven pad or rotor wear.

Even the D-Series Rotor was designed to increase braking performance. The rotors are intentionally designed to oppose the resonant frequency of both the Semi-Met T106 and Sintered T100 pads that the brakes are shipped with. What does this mean? It means that the brakes were designed to cancel out noises and vibrations caused while braking, translating to more consistent braking.

Hayes Dominion A4 Brakeset Review


Decades ago, my first hydraulic disc brakes were the legendary Hayes Mags. I can remember how much better they worked than the V-brakes on my previous bike. I can also remember thinking I was going to need a heat guard similar to what motocross bikes run. My three next bikes all had Hayes Mag brakes and I was hooked.

After those first few Hayes-equipped bikes I ended up on some bikes with Hayes Stroker Ace brakes in the late 2000’s. If you rode those brakes too you probably understand why I immediately took them off my bikes and switched to another brand for good.

Those memories were in the back of my mind while installing the Dominion A4 brakes on my new bike. I was excited, hopeful and honestly, a bit skeptical too. I wanted them to work and reignite my nostalgic love for Hayes. The time was now.

Installation is straight forward. Hayes included everything I needed to bleed the brakes after cutting the hoses to match the other cables on my bike. Hayes has loads of information online to make cutting and bleeding easy for even the novice bike mechanic.

Hayes Dominion A4 Brakeset Review

The Dominion A4 lever is comfortable with or without gloves and has incredibly smooth operation. As stated above, the lever rolls on ball bearings and it really makes for smooth actuation. The lever also includes an integrated reach adjustment dial that is tucked into the lever to protect it in the event of a crash. The lever adjustment is easy to use with or without gloves.

Hayes did a really great job with the Dead Stroke, lever feel and the lever action. The brakes start to engage as soon as there is pressure on the lever and modulation is great. Increased pressure means more braking power until the brakes lock up. As soon as the lever is released the brakes release and there is an audible click that can be heard when the lever returns to its original position.

What really surprised me about the Hayes Dominion A4 brakes during the course of my review is that the brakes feel the same today as they did on my first ride. The lever contact point and modulation has remained the same time and time again. Every time I have pulled these brakes they feel the same: Same lever contact point, same pad contact point, same pressure, same braking power… This makes the Dominion A4 extremely predictable brake, which is something that I really enjoy in a brake, and as a rider over 200lbs who likes riding steep trails in the woods of British Columbia, that is not something I find in all brakes.

Hayes Dominion A4 Brakeset Review

The Wolf’s Last Word

Hayes took their time when designing and testing the Dominion A4 and it shows, and quite honestly they needed to. It was smart of them to take the extra time and unveil a product that would really catch the attention of riders who’d either never heard of Hayes or had dismissed them 20 years ago. Now the hard part of keeping their brand visible becomes the challenge, because they’ve clearly tackled the hurtle of creating a high quality brake.

The small details Hayes thought of like the reach adjustment location on the lever, the dead stroke adjustment hidden in the lever’s push rod and the Crosshair Caliper Alignment System shows the amount of time that they put into these brakes. And the consistent and reliable performance over the last several months has proven to me that the updates are more than superficial.

It is time for mountain bikers to give Hayes brakes a second…or third chance? I was pleasantly surprised by the Dominion A4 brake and I think most riders will be as well.

Price: $183.99 each
$39.99 – Rotor;
Weight: 316g (front brake only, no rotor);
Website: Hayesbicycle.com

We Dig

Stopping Power
Lever Feel
Crosshair Caliper Alignment
Instant Engagement

We Don’t

Nothing Yet


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