Hayes Dominion A4 disc brake comparison: The pads ruined everything

Conclusion on the Hayes Dominion A4

Despite the laboratory debacle, we would like to recommend the Hayes Dominion A4 to anyone who places great value on reliability, fine modulation and plenty of fine-tuning potential. With the right pads, the power is completely sufficient in practice, but at the limit you can feel a clear difference compared to the most powerful systems on the market. - Max Fuchs, BIKE Editor

The laboratory test of the Hayes Dominion was unfortunate. For a clean comparison, all brakes were tested with the pair of pads that are also supplied to the end customer. In almost all cases, the manufacturers rely on organic compounds. They work particularly well in dry conditions, deliver a powerful initial bite even with little heat in the system and work pleasantly quietly - in short: the ideal all-round pad. Many riders accept the fact that most organic rubbers deteriorate in the wet. After all, in practice, dry rides predominate.

Technical data: Hayes Dominion A4

Incorrect brake pad for the Hayes Dominion A4

Hayes includes two pairs of pads: an organic all-rounder and a metallic specialist. Metallic rubbers only really feel at home at high temperatures and really come into their own under extreme conditions. The metal fibres in the compound also perfect the wet performance. The downside: less deceleration during "cold starts", lower dry braking performance and a significantly higher noise level. Nevertheless, Hayes advised us to use the metallic compound. According to the manufacturer's recommendation, it allows you to get the most out of the brakes.

A topsy-turvy world on the brake test bench

Unfortunately, the exact opposite happened. During dry braking, the Dominion A4 ended up in the bottom third of the test field. The Hayes only reaches the practice-relevant maximum braking power of around 600 newtons - above which there is a risk of rollover - at 120 newtons of manual force. The majority of the test field already reaches this value at 80 newtons. In other words: the power is there, but it is difficult to call up. In wet braking, on the other hand, the Dominion A4 shines with its metallic brake pad and achieves the highest value. To show how strongly the pad influences the braking effect, it is also worth comparing the wet and dry braking of the Hayes itself: In the wet, it delivers even more braking power at 80 newtons of force than in the dry.

The Dominion A4 is still worth a recommendation

With the right pads, the Dominion A4 has no power problems in practice. What's more, the lever geometry and response behaviour are impressive across the board. No other brake offers such precise lever travel. Breakaway torque? Not a thing. The initial bite can be felt with surgical precision. The candidate only reacts with real bite at medium hand forces - perfect for loose and slippery surfaces. The rounded lever with perforated surface turns out to be a real hand flatterer. The lever reach adjustment covers a very wide range. Good for anyone who wants to bleed their brakes perfectly: There is a bleed screw on the left and right side of the brake calliper. One grub screw per slotted hole on the brake calliper helps to adjust the brake one hundred per cent without dragging.

The BIKE rating

How BIKE tests disc brakes

Our impressions of the character, modulation and handling come from practical tests. We determined the maximum braking power and thermal stability in accordance with the DIN standard on the roller test bench of the brake manufacturer Magura.

• Braking force test in the laboratory: To ensure that the brakes can deliver their maximum performance on the test bench, the test standard prescribes a defined braking procedure. All models must maintain a constant braking force of 200 newtons over 20 braking intervals in order to come up to temperature and rule out pad fading during the brake force test. Only then does the actual test of strength begin. It consists of three brake applications per force applied to the lever. It starts with 40 newtons of manual force. The test stand increases the force on the lever in 20 Newton increments until the brake reaches its maximum lever travel. Each brake undergoes this procedure twice: once in the dry and once in the wet. During wet running, the disc is continuously wetted throughout the entire measurement. For an optimum comparison, all models run with 180 mm discs. The pad compounds always correspond to the standard equipment. The manufacturers were allowed to select the discs themselves - if several options are available in their own range - in favour of braking performance. For uniform comparative values, we carry out the braking force test and the heat resistance test with a fresh pair of pads and a new brake disc. For the evaluation of braking performance in the laboratory, we only use the results at 80 N manual force. In this range, all models still deliver practice-relevant values below the 600 N threshold, especially during dry braking. Above this level, there is a risk of rollover under ideal grip conditions.
  
• Heat resistance: As a second hurdle in the laboratory, all brakes have to pass a standardised heat resistance test twice. After all, the candidates should decelerate reliably even under high thermal loads. The programme includes three endurance braking sessions of five minutes each. Shortly after each interval, an abrupt control brake application follows, which shows whether the brakes still decelerate perfectly despite the heat. Finally, the test bench calls up the required minimum braking force three times. All brakes passed this test.
  
• Practical test: No test bench can measure how a brake develops its power off-road, how it reacts to low manual forces, how finely it can be metered and how it feels in the hand. This is where experience counts. And our testers have plenty of it: over 100 complete bikes go through our test procedure every year. Our editors therefore know most of the brakes inside out. In addition, two testers rode all the brakes in this test in direct comparison on standardised bikes with identical setups.

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