Hayes' Dominion A4 brakes have garnered a strong contingent of loyal fans in the years since their introduction back in 2018, and now there's an even lighter version on the way called the T4 that uses carbon fiber lever blades, titanium hardware, and additional machining to shed as much weight as possible. All of those measures allowed Hayes to reduce the weight of each brake by 50 grams, for a total weight savings of 100 grams per set compared to the A4 version.
Hayes aren't claiming to have created the absolute lightest brakes on the market, but at 257 grams per wheel the T4's are lighter than SRAM Codes by around 40 grams, and 5 grams lighter than Shimano's XTR 4-piston brakes. Brakes aren't typically the first place most riders go to save weight, but if the power and performance remain the same it certainly doesn't hurt to knock a few extra grams off the scale.
Hayes Dominion T4 Details
• 17mm pistons
• Reach adjust, pad contact adjust
• Claimed weight: 257 grams (90cm hose + mounting hardware)
• DOT 5.1 fluid
• Price: $325 USD per brake
The spec sheet claims that the T4's reach adjust is still a tool-free affair, but that doesn't appear to be the case – the dial found on the aluminum lever blade isn't anywhere to be seen on the carbon blades, which are produced by Reynolds, Hayes' sister company. Adjusting the lever reach and pad contact is still possible, you'll just need to use an Allen key to make those tweaks.
All of the Dominion's other features are still in place – the brakes use DOT 5.1 fluid, with four 17mm pistons in each caliper. The caliper body has seen extra machining to remove any excess material, and there are little depressions on each side that are probably worth a few grams of weight savings. Thankfully the set screws that help get the caliper perfectly aligned haven't gone anywhere – that clever feature helps set the Dominions apart from other brakes on the market.
The Dominion T4's bolts, push rods, compression and banjo fittings are all titanium, and there are composite reservoir covers to lighten things up even further, along with aluminum back plates on the brake pads.
Not surprisingly, all of that carbon fiber and titanium does raise the final price – the Dominion T4 brakes are priced at $325 USD per wheel, compared to $250 for the Dominion A4. The aluminum-backed T4 pads are $38.99 USD.