TRP Evo X and Evo Pro Brakes

The PAD adjusts the amount of free stroke in the lever by moving the cam that sits between the lever blade and the pushrod for the master cylinder, effectively moving the starting point of the master cylinder piston closer to or farther from the timing port inside the lever. That varies how much dead stroke there is before the piston passes the timing port and starts to push fluid down the line, actuating the pistons.

[If some more background on what I’m talking about in that last paragraph would help, here’s how I described the concept in our review of the Hayes Dominion A4 brakes a while back:

Modern hydraulic disc brakes for bikes operate on a semi-open system, meaning that the lever features a reservoir of “extra” hydraulic fluid that’s connected to the brake line when the lever isn’t being squeezed. This allows them, in part, to compensate for things like pad wear and thermal expansion of the brake fluid, as well as having a greater volume of brake fluid available to better transfer heat out of the system. When you squeeze the brake lever, the lever piston moves past the hole connecting this reservoir to the brake line (called the “timing port”) and closes it off. Only once the timing port is closed does the brake start to move fluid through the hose to the caliper, and build pressure to provide braking force.

The adjustable free stroke can be helpful for making both levers feel more similar if there’s a slight difference in piston rollback between the two calipers, a little extra hose expansion in the longer rear line, or whatever else. It’s also possible to make the free stroke significantly longer than it is with the PAD adjuster turned all the way in, though I don’t imagine that most people will want to do so on what is a pretty high-power, high-leverage gravity brake with a not especially short free stroke to begin with.

The Evo Pro lever still features a tool-free reach adjuster, but it now sits on the front side of the lever blade rather than being tucked behind it as on the DH-R Evo. And speaking of the lever blade, TRP has moved the pivot point quite a bit closer to the bar, and along the way, given the Evo Pro a much more usable range of reach adjustment. It’s now possible to run the lever much, much closer to the bar than it was on the DH-R Evo, and the main face of the lever blade sits much more parallel to the bar with the reach set at the shorter end of the range. I wasn’t able to get the reach as short as I wanted with the DH-R Evos (at least not without resorting to aftermarket lever blades); I have no such issues on the Evo Pro.

Another more subtle but also important ergonomic upgrade with the new lever is the inclusion of a cam between the lever blade and the master cylinder pushrod. TRP says that maintaining the smooth, linear power delivery of the DH-R Evo was an important consideration with the new brakes, and rather than changing the Evo Pro lever’s leverage curve, the new cam aims to help maintain a consistent feel across different reach settings. With the DH-R Evo, the lever blade was tied directly to the master cylinder pushrod, which meant that adjusting the reach also changed the brake’s leverage curve as a side effect. In practice, that meant that running the brake levers closer to the bar on that brake resulted in a softer bite point. That’s gone on the new lever, with the lever blade free to adjust in and out on its own.