On the heels of their RT8 TT hydraulic rim brake for time trial bikes, Magura this week released a converter for standard road bikes. Without a finalized name yet, it mounts to the steerer tube and is designed to be used with the company’s RT8 hydraulic rim calipers. We borrowed Magura’s Cervélo test bike at the Sea Otter Classic to test ride the setup on the rolling hills around Laguna Seca.
The system provided good modulation and strong, predictable braking. In order to stop quickly from high speed, you had to pull the lever a fair way but the hand force required was noticeably less than a standard cable-operated setup. That said, the system did feel less powerful than hydraulic disc brakes. These were just first impressions, and unfortunately we don't have a quantification of the difference.
Unlike a standard “open” hydraulic disc brake system, the Magura converter is closed, meaning there's no reservoir. “With mountain bikes, you’re dealing with a lot of heat going into the fluid,” Magura’s Tony Ballantine told BikeRadar. “A hot rotor transfers heat into the pistons, which goes into the fluid. That fluid needs to expand and that’s why you have a reservoir. Here, the fluid isn't changing temperature because all the heat is in the pad and in the rim.”
Here’s how the Magura converter works. Each brake cable runs from the lever into the converter box. Inside, the cable pulls on a pivoting lever that depresses a plunger to activate the hydraulics. On the other end, the slave cylinder presses up against the caliper arms, which each leverage on their own pivots to press a standard road caliper pad against the rim.
The converter box is made of “carbotexture”. Translation? Injection-molded carbon fiber. It’s the same process and material that Magura use for the master cylinders on their top-end mountain-bike brakes. At Sea Otter, Magura didn't yet have a weight to quote for the converter. It'll retail for $800, including the RT8 calipers.