HayesDominion A4
€278 RRP per brake (one wheel), Hayes EU web store (eu.hayesbicycle.com), EUR; same price for SRL and Purple Hayes versions
- Pistons
- 4 x 17 mm
- Fluid
- DOT 5.1
- Hose
- Kevlar, 180 cm
- Bleed
- Two-Stroke dual port
- Lever
- Tool-free reach adjust; SRL short-reach option
- Weight
- 310 g
- Weight
- 310 gper brake, claimed
Overview
Hayes' four-piston Dominion A4 (4 x 17 mm pistons, 310 g, DOT 5.1), pitched for enduro, downhill and eMTB riding; RRP 278 EUR per brake on Hayes' EU store.
The Dominion A4 is Hayes' award-winning four-piston hydraulic disc brake for aggressive trail riding. Hayes says its heat management makes it ideal for long descents, sustained braking and the high-load conditions common in enduro, downhill and eMTB riding, and that it is built to handle heavier bikes and faster speeds without fade. The master cylinder is factory-tuned for the shortest possible dead stroke and a crisp bite point.
The cold-forged caliper uses four 17 mm pistons and a KingPin structural pad-retention bolt for stiffness, with Crosshair caliper alignment screws for setup. The hydraulic system runs DOT 5.1 fluid through a Kevlar hose with a motorsport-inspired Two-Stroke dual-port bleed, and the QuickBite² system pairs with Hayes' D-Series rotors for fast burnish and less noise. It is also sold with the SRL (Short Reach Lever) for smaller hands, and in a limited 'Purple Hayes' colourway.
- Four 17 mm pistons in a cold-forged caliper
- Hayes names eMTB, enduro and downhill as ideal uses
- DOT 5.1, Kevlar hose, Two-Stroke dual-port bleed
- Tool-free reach adjust, flip-flop lever, sealed-bearing pivot
- Semi-metallic pads fitted, sintered pads in the box
Gallery
Full specifications
Caliper
- Pistons
- 4 x Ø17 mm
- Caliper
- Cold-forged
- Pad retention
- KingPin structural bolt
- Alignment
- Crosshair caliper alignment
- Pads
- Semi-metallic installed, sintered in the box
Lever
- Reach adjust
- Tool-free
- Lever orientation
- Flip-flop
- Lever pivot
- Sealed cartridge bearings
- Lever options
- Regular; SRL (Short Reach Lever)
Hydraulics
- Fluid
- DOT 5.1
- Bleed
- 2-Stroke dual-port bleed system
- Hose
- Kevlar
- Hose length
- 180 cm (SRL: 100 cm front / 180 cm rear)
General
- Weight
- 310 g
- Colours
- Stealth Black/Grey, Bronze; limited Purple Hayes edition
- Recommended rotor
- Hayes D-Series with QuickBite²
- Intended use (Hayes)
- Trail, enduro, downhill, eMTB
- US price
- US$249.99 per brake
Manufacturer specification — Hayes. Specs and prices can change; check with the brand or your dealer.
Hayes Dominion versions compared
| Dominion A4 | Dominion T4 | Dominion A2 | Dominion T2 | |
|---|---|---|---|---|
| Price | €278 | — | €139 | — |
| Pistons | 4 x 17 mm | 4 x 17 mm | 2 x 24 mm | 2 x 24 mm |
| Fluid | DOT 5.1 | DOT 5.1 | DOT 5.1 | DOT 5.1 |
| Hose | Kevlar, 180 cm | — | Kevlar, 100 cm front / 180 cm rear | K2, 100 cm front / 180 cm rear |
| Bleed | Two-Stroke dual port | — | — | — |
| Lever | Tool-free reach adjust; SRL short-reach option | Carbon fibre, tooled reach & pad-contact adjust | Tool-free reach adjust; SRL option | Carbon fibre, tooled reach & pad-contact adjust |
| Weight | 310 g | 257 g | 303 g | 254 g |
| Rotor sizes | — | 160 / 180 / 203 mm (D-Series) | — | — |
| Weight | 310 g | 257 g | 303 g | 254 g |
| E-bike rated | Yes | — | — | — |
eMTBs that come with the Hayes Dominion
Hayes Dominion A4: FAQ
How much does the Hayes Dominion A4 cost?
€278 (RRP per brake (one wheel), Hayes EU web store (eu.hayesbicycle.com), EUR; same price for SRL and Purple Hayes versions). Prices vary by country and retailer.
How much does the Hayes Dominion A4 weigh?
Hayes quotes 310 g (per brake, claimed).
Is the Hayes Dominion A4 suitable for e-bikes?
Yes — Hayes lists it as e-bike rated or e-bike specific.
What are the key specs of the Hayes Dominion A4?
Pistons: 4 x 17 mm; Fluid: DOT 5.1; Hose: Kevlar, 180 cm; Bleed: Two-Stroke dual port; Lever: Tool-free reach adjust; SRL short-reach option; Weight: 310 g.
What other versions of the Hayes Dominion are there?
Dominion T4, Dominion A2 (€139), Dominion T2.
