Hayes Dominion A4 Hydraulic Disc Brake

For a long time, the US American cult brand Hayes did not have any news regarding high-end disc brakes for trail, enduro, downhill and e-MTB riding. With the Dominion A4, the brake specialists from Milwaukee fight their way back into the game for the best high-performance brakes.
The extremely robust four-piston brake caliper made of cold-forged aluminium, the massive sensor unit with bearing-mounted lever blades, the high-performance K2 Kevlar brake hoses and last but not least the brake’s name clearly show what the Hayes developers have designed the Dominion A4 for: They wanted to challenge the established top dogs for the control over the disc brake market!

For this ambitious task, they’ve completely revised the 4-piston brake caliper and fitted it with a motorsports-inspired 2-Stroke Dual Port Bleed System. Put more simply – the caliper has two separate bleed ports to guarantee no air bubbles hanging about anywhere in the system. In addition, the pad retention bolt is integrated into the design and has an additional task. As a third bolt, it increases stiffness at the brake caliper and is called “KingPin”. High-quality aluminium pistons guarantee constant braking performance under high loads as well as effective heat management.
The CrossHair alignment system by Hayes is of course a must-have for the Dominion A4. Two little grub screws at both caliper ends allow you to easily and quickly adjust the caliper position. A simple but genius design feature.

Just like the large reservoir of the lever body. After all, Hayes has designed the Dominion A4 to offer not only outstanding braking power but also perfect modulation. The bearing-mounted brake lever impresses with smooth running and excellent ergonomics. A large and comfortable tool-free reach adjust dial allows you to precisely adjust the lever reach, even when wearing gloves. Besides, there’s a tiny hidden grub screw to set the dead stroke.
Every single Dominion brake lever is factory tuned for minimum dead stroke possible to produce immediate pad contact (this can be changed to produce more movement). Thus, the actual “dead stroke” is reduced to the distance between brake pad and disc rotor. The result is a crisp bite point and a linear increase in braking power through to maximum deceleration.

A space-saving split handlebar clamp allows for easy installation on the bar. There is the option to fix SRAM Matchmaker or SHIMANO I-Spec 2 compatible shifters directly on the lever blades of your Dominion A4 using the Hayes Peacemaker clamps – for a neat cockpit and a clean look.

Details:
• Hydraulic high-performance 4-piston disc brake for trail, enduro, downhill and e-mountain bikes
• Compatible with Hayes Peacemaker
• Laser etch graphics
• CrossHair Alignment: alignment system for perfect brake caliper adjustment
• Bearing-mounted brake lever for an improved feeling
• LoFi Technology: “LoFi” stands for Low Input force and High Fidelity Output Force and ensures increased braking power with less hand force
• King Pin Technology: pad retention bolt that additionally serves as a third bolt for increased stiffness at the caliper
• 2-Stroke Dual Port Bleed System: Two separate bleed ports on the brake caliper for safe bleeding

Tip:
For a video on how to cut the brake hoses and how to bleed the Hayes Dominion A4, please visit the product page of the Hayes DOT 5.1 Pro bleed kit (product code: 2289161).

Specs:
Material:
• Brake levers: aluminium
• Brake caliper: cold-forged aluminium
• Brake piston: aluminium
• Brake hose: K2 Kevlar

Adjustments:
• External lever reach adjustment (tool free)
• Pad contact adjustment (hex)

Others:
• Brake levers: flip flop design (for installation on the right and left side of the bar)
• For handlebar Ø: 22.2 mm
• Brake caliper: post mount
• Brake fluid: Hayes DOT 5.1
• Brake pads: semi-metallic or metallic
• Recommended disc rotor (optional): Hayes D Series (product code: 2289162)
• Weight: approx. 310 g (incl. 900mm brake hose and mounting material)

Available in:
• Front wheel (hose length approx. 1000 mm)
or
• Rear wheel (hose length approx. 1800 mm)
Please make your choice.

In the box:
• 1x Hayes Dominion A4 disc brake (front OR rear wheel), filled and bled ready for installation
• 1 pair of semi-metallic brake pads
• 1 pair of sintered brake pads (metallic)
• Mounting material
Note:
Delivered WITHOUT disc rotor and WITHOUT adapter!

• Optional accessories:
• Hayes D Series disc rotor 6-bolt (product code: 2289162)
• Hayes Peacemaker handlebar clamp for SRAM Matchmaker (product code: 2289164)
• Hayes Peacemaker handlebar clamp for SHIMANO I-Spec 2 (product code: 2289163)
• Hayes disc brake adapter PM6 (160mm) to PM8 (203 mm) (product code: 2289166)
• Hayes disc brake adapter PM7 (180mm) to PM8 (203 mm) (product code: 2289167)
• Hayes DOT 5.1 Pro bleed kit (product code: 2289161)

Manufacturer: Hayes Performance Systems, 5800 W Donges Bay Rd, Mequon WI 53092, USA, hayesbicycle.com/
Responsible person: MERIDA & CENTURION Germany GmbH, Blumenstraße 49-51, 71106 Magstadt, Germany, www.mcg-parts.de