Hayes Brake Bounces Back with the Dominion A4 3

Once the go-to disc brake for mountain bikers, Hayes re-emerges from near silence with data acquisition on their side.

Hayes Brake Bounces Back with the Dominion A4

Following several years of silence, Hayes is back in a big way with the introduction of their new Dominion A4 disc brake. Hayes has a long history in the mountain bike world and is responsible for bringing disc brakes to the scene many years ago. New for 2019 they’re introducing the all-new 4-piston brake design that is the result of extensive real-world data acquisition in an effort to bring their brakes up to date. Through the use of various data acquisition systems, they determined that a drop in the ultimate power of a brake would help increase the useable power range for riders.

The lever uses what they call LoFi, which essentially combines low effort on the part of your fingers with a high clamp force at the caliper. They describe their brakes as feeling detectable but manageable. The lever features a tool-free reach adjust, a tooled pad contact adjustment, cartridge bearings for smooth actuation, and aluminum piston.

Another interesting feature is that the caliper has two bleed ports, which Hayes refers to as Two Stroke. They’ve used this dual bleed port design to allow you to get air from behind all calipers which Hayes sites as a common issue in the mountain bike world.

This is their stiffest caliper to date and it features Hayes’ Crosshair Alignment system which are essentially set-screws on the side of the disc brake near the mounting tabs. These allow you to precisely align the brake so your rotor doesn’t rub.

Hayes did a fair amount of research and development in regards to brake noise and claim that the natural resonance of the rotors and the pads cancel one other out providing a quite ride. The brakes use DOT 5.1 fluid and have 17mm pistons. Retail is $230 per brake, $50 per rotor.



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sspomer 7/8/2018 4:37 PM

3 comments newest first

Honestly, this brake sounds freaking sweet. Hayes have brought some innovation here and if it delivers how they promise then it could be a serious contender.

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They definitely did a good job realizing the short-comings and rider complaints of other brakes. I really like the dual bleed port on the caliper, Having all four pistons function evenly shouldn't be hard to achieve with these.

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