Hayes Dominion A4

Overview

The award-winning Dominion A4 is Hayes most capable hydraulic mountain brake, engineered from the ground up for modern trail, enduro, and e-MTB use. A cold-forged four-piston caliper with four Ø17mm pistons sits at the heart of the system, delivering extreme-duty stopping power. The proprietary LOFI (Low Input – High Fidelity) philosophy ensures a featherlight, progressive lever feel with a crisp, factory-set bite point. Motorsports-inspired Two-Stroke dual port bleeding with DOT 5.1 fluid and Kevlar hose guarantees a rock-solid hydraulic system in all temperatures. The QuickBite² system speeds up pad break-in, while the D-Series rotor pairing applies FEA-optimized Modal Resonance Cancellation (MRC) to eliminate brake noise.

Features

• Award-winning (Design Innovation Award) Dominion platform

• Cold-forged 4-piston caliper with four Ø17mm pistons

• LOFI: progressive ramp-up with crisp factory-set bite point

• Sealed ball bearings at lever pivot for featherweight lever feel

• Stable Rate Link (SRL) — consistent lever ratio regardless of reach

• KingPin structural pad retention bolt for caliper stiffness

• Two-Stroke dual port bleed system for maximum integrity

• DOT 5.1 fluid and Kevlar hose for all-temperature performance

• QuickBite² system for rapid pad bedding

• Available with SRL Short Reach Lever option

• Compatible with D-Series MRC rotors for vibration cancellation