American brake giant Hayes has been conspicuous by its absence in the bike industry of late. But this is all about to change thanks to the arrival of a brand new brake that it thinks will boost it straight back to the top of the brake tree.

Called the Dominion A4, it has been developed from scratch with zero parts from any of Hayes’ existing brake sets. It’s a four piston brake aimed at trail, enduro and downhill riders. To keep up with today’s fashions Hayes also recommend it for eMTB use.

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The lever not only features tool-free reach adjust but pad contact can also be adjusted.

Dominion A4 Need to Know

Lever –

• New lever design and master cylinder use Hayes’ LoFi system – Low lever input produces High output force. Hayes claim the Dominion A4 is one of the most powerful brakes on the market.
• Each lever/master cylinder is individually calibrated to produce immediate pad contact – this can be changed to produce more movement.
• Lever features tool free adjustment and tooled pad contact adjustment. It runs on cartridge bearings and has an aluminium piston that runs on glide rings (technology pioneered in suspension forks) for super smooth movement.

Glide rings (the white bits) make piston movement super smooth. Cartridge bearings keep lever feel consistent.

Caliper –

• The Dominion A4 caliper is Hayes’ stiffest yet.
• Dual bleed ports for totally reliable bleeding.
• Kingpin structurally integral pad retention bolt
• Four 17mm diameter pistons
• Crosshair alignment screws make setup a doddle.

Four 17mm diameter pistons sit in a super stiff calliper body. Dual bleed ports stop any pesky air bubbles from sitting behind the pistons.

System –

• Weights: Dominion A4 – 310g (90cm front system, hose, caliper, T106 pads, and caliper mount bolts). D-Series Rotor – 160g (180mm), 200g (203mm) including fasteners
• Price: Dominion A4 – (front or rear) £199.99 RRP. D-Series rotor – (180mm or 203mm) £49.99 RRP
• Availability: Autumn 2018

Whilst Hayes has been missing from the MTB scene, it hasn’t been missing from the brake scene. In fact Hayes is predominately a brake manufacturer for our motorised brethren and as such has not stopped developing and improving its knowledge and brake technology while it’s been away.  When Hayes decided to step back into the MTB world with the Dominion its developers went back to basics and really thought about how modern riders use their brakes. You see, riding styles have moved on from five years ago with more and more riders pushing into longer travel and more aggressive riding. These changes require a different approach to how brakes are used; and ultimately which designs work and which do not.

Years of data acquisition and working with a team of test riders saw Hayes go through multiple prototypes. Changing everything from lever materials and shape, hose types, pad materials and rotor designs before settling for the system you see before you.

The new D-Series rotor is shaped to cancel out the resonance frequency of the brake pads. Hopefully this will make the Dominion noise free.

Noise free rotors

Apart from the key characteristics of the lever and caliper, the most interesting feature is probably the new D-Series rotor. Using something called Modal Resonance Cancellation, it has been shaped in such a way that the design’s resonance frequency effectively opposes the resonance frequency of the pads. In doing so this theoretically should cancel out noise and vibration and make your brakes work more consistently. Rotor thickness is 1.95mm, so a touch thinner than most common types.

Hayes has sent us a full set of the Dominion A4 to test, so look out for our first impressions soon.