Promising excellent air penetration – when mounted to a suitable cycle – thanks to aerodynamics by Cervelo, Magura’s new RT8 TT brakeset is also said to be, at 495g, the lightest complete rim brake assembly on the market. Add to these highly-desirable features the precision, low maintenance requirements and efficient force transfer of hydraulic operation and the German firm’s latest offering looks set to be one of the big hits of 2012.
Featuring brake levers designed for installation on “aero”-style handlebars, it is aimed squarely at the time trial and triathlon market. The caliper’s standard dimensions mean that it will fit a road bike’s frame and forks, but the near-universal use of dual-control brake and gear shift levers on such machines means that Magura will have to design some sort of adaptor or suitable lever before hydraulics makes it to the world of the dropped handlebar.
The basics of hydraulic operation are simple – pressure within the fluid chamber is equally distributed and applied independently of its shape. This means the hose can be curved to fit through tight internal spaces inside handlebars with no effect on braking performance. The equal pressure applied on all internal surfaces makes it easy to engineer any desired brake force ratio between the lever and the brake blocks, while the incompressibility of the fluid ensures there is no loss of force as the brake is applied.
Housed in forged aluminium bodies with patented expander mount, the all-carbon-fibre levers each feature a quick-release function, ergonomically-shaped contact points, reach adjustment and twin “airfoil” arms. Superficially similar to designs such as Campagnolo’s Delta and even Shimano’s Parapull, the caliper silhouette minimises frontal area. The operation of the internals is, of course, somewhat different, with a piston and rod applying pressure in place of a cable acting in tension. At the tip of the rod is a prism-shaped wedge with angled faces that push against rollers on the tips of the caliper arms, forcing them apart as the rod moves upwards. Imagine “centrepush” instead of “centrepull”. The arms pivot at their middle on ball-bearings and locate “universal” Shimano/SRAM-type cartridge shoes and pads in adjustment slots. Attachment to the fork or stay is via a conventional top-hat nut while a hairpin spring provides the return function.
Careful attention to master and slave cylinder ratios, caliper arm length and rod wedge angles dials what Magura says is the best braking performance available. Expect both power and modulation to be appreciably superior to the best cable operated dual-pivot calipers thanks to the advantages conferred by hydraulic operation, which in this case acts through the medium of Magura’s Royal Blood mineral oil. Each caliper has a bleed port for easy refill, although Magura says that, unlike regular DOT brake fluid, the oil does not need frequent replacement. In any case, the firm offers a five-year warranty against fluid loss from the hose.
Price for the RT8 TT will be based on €599, with the less expensive RT6 version, which has aluminium lever arms, going for €499. Cervelo has a one year manufacturer exclusive on the new brake, which has received UCI approval. More on availability soon.
