A quality brake with tons of power and modulation from Hayes.
In a world of rising prices everywhere you turn, it’s pleasing to see that the Dominon A4 costs the same as it did the last time we tested it, two years ago and it’s still one of the best MTB disc brakes. The A4 is still sold without rotors and adapters, so adding a D-Series rotor and adapter is going to add about £55 a wheel, but it’s still great value and top quality. In terms of weight, the Dominion A4 lever/caliper is heavier than the SRAM G2 Ultimate, but Hayes claws some of that back by using a lighter stainless-steel rotor. The standard D-Series steel rotor is a bit pricey but it was straight and didn’t show any signs of warping during testing.
One of the unique features on the Dominion A4 is the Crosshair caliper centring, which is essentially two tiny grub screws on the caliper tabs that push against the fixing bolts, allowing you to precisely fine-tune the caliper position and eliminate rubbing. This is a clever feature, but we never really needed to use it because the brake has really good pad clearance that makes drag-free set-up a doddle. The Dominion A4 uses standard 1.95mm thick rotors, but the lever pulls in quite far before the pads actually bite. The knock-on effect of that is it also renders the reach adjustment less than useful – if we brought the lever really close in, it’d bottom out on the grip before the brake fully activated.
To match different hand sizes, the lever gets a dialled reach adjustment, which is also indexed, so it won’t work loose or migrate. Hidden behind the lever is a contact point adjuster, but it’s set to be as close as possible out of the box, and we never really wanted the brake to pull further, so we left it there. The lever has a broad, comfortable shape for one-finger braking, but it is a little bit short, and during testing we had to move the shifter farther outboard to reach it – for this reason we’d recommend Hayes matchmaker style mount to stop the shifter getting in the way. If you’re coming off a SRAM brake you will notice the difference
The Dominion did bed in really quickly, and with cartridge pivot bearings, it has a light lever action. The power delivery is good too and, when you really need it, there’s plenty in the tank. Compared to previous Hayes brakes, which always a bit on/off the Dominion is really well modulated, with a lightweight lever action and a smooth build-up of power.
Compared to the Dominion A2, there’s barely any difference in weight or price, so you could run the A4 with a smaller rotor to end up with lighter, more powerful system for an extra £20.
Some of the adjustment features are a little superfluous, but they are there if you need them. Overall, it’s a top stopper; solid, reliable and still great value.