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Dominion A4 Disc Brake

5 out of 5 stars
1 Review



Dominion Disc Brake

Hayes brakes have fallen off of many rider's radars for some reason or another, however, we must remember that it was instrumental in bringing disc brake technology to mountain bikes over 20-years ago. The brand has plenty of experience in motorsports and the technology it brought to the table was truly game-changing. A lot has changed in 2 decades and in recent years, other brands have entered the fray and put Hayes on its back foot, but with the introduction of its new Dominion Disc Brake, it's slated to once again be a major player and has a brake that's packed with truly innovative features that's destined to put Hayes right back on the map.

There are plenty of brakes on the market with outright stopping power, but the key to providing confident braking is making sure plenty of modulation and feel is built-in so it isn't so much of a light switch, on, off experience. Starting at the tool-free reach adjustable lever, Hayes employs cartridge bearings at the pivots to reduce drag and provide stiff points of contact so you get a positive lever feel with zero slop. The Dominion’s master cylinder is designed with an extremely short dead stroke and with its revised cam profile when the pads contact the rotor, it comes with a crisp bite point. Joining the master cylinder to the rest of the system is a flex-free hose and high-performance DOT 5.1 brake fluid.

Moving down to the caliper, it features cold-forged construction and is engineered to be as rigid as possible and utilizes four pistons to move the pads, again contributing to that excellent power and modulation. Even the KingPin pad retention bolt is designed as a structural member to help increase stiffness. Also at the caliper are our two favorite "why hasn't anybody else thought of this" features of this brake. The first is its Two-Stroke dual port bleed system on either side of the caliper. With two bleed ports, it ensures better bleeds and improves the ability to evacuate air making sure spongy brakes are a thing of the past. The other feature is its Crosshair Caliper Alignment System which uses caliper alignment screws that allow for quick and easy alignment with no rotor rub or frustration.


  • Hayes answer for increased power and modulation in a brake
  • Stiff 4-piston caliper improves power
  • Better modulation allows for precision on technical trails
  • Dual caliper bleed ports ensure air-free bleeds
  • Revised lever pivots, piston, and stroke give a positive feel
  • Crosshair caliper adjustment makes for easy setup and adjustments
  • Package with pre-bled lever/caliper/hose assembly
  • Flex-free hose and DOT 5.1 fluid provide high-performance
  • Item #HAY0003
Lever Adjustability
Dominion A4
Caliper Adjustability
Crosshair Caliper Alignment System
Mount Type
DOT 5.1
not included
Claimed Weight
10.9oz (310g)
Manufacturer Warranty
Lifetime Leakproof

Overall Rating

5 based on 1 ratings

Review Summary

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5 Stars - 1 reviews

Fits True To Size

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5 out of 5 stars

May 16, 2024

Awesome Brakes

I've used it several times
Size Bought:

Best modulation and stopping power that I've experienced in a hydraulic braking system. Highly recommend.