A brief history of the radial master cyclinder

4/27/2017

The secret to the impressive response linearity found in the radial master cylinder that substantially improves braking performance.

​In 1985 Brembo registered the first patent for an idea destined to revolutionise braking systems: the radial master cylinder. The idea first took shape in racing, where the problem of limited space on competition bikes spurred intense research into more compact solutions.

This new concept significantly improved rider ergonomics, making the action of the rider on the brake lever even more effective while reducing the size of the system.

 

 

What set this new solution apart was a configuration that transmitted the force exerted by the rider's hand to the piston directly and in the same direction, without friction losses caused by diverting the force into multiple components.

The radial design puts the piston axis parallel to the lever pull direction and perpendicular to the handlebar.

One of the many advantages of this approach was that the brake master cylinder could be designed to optimise the hydraulic and mechanical ratios in order to improve the product's performance.


 

​In 1986 the radial master cylinder was already on the track, on the Yamaha YZR OW of the famous GP racer Eddie Lawson, who would win that season's 500 cc class of the Motorcycle Grand Prix.

The American was immediately impressed by the extraordinarily linear response of the new component, convincing Brembo to develop the idea further to resolve a few shortcomings that the new solution had brought to light.


 

 

​Two further evolutions of the initial concept were patented in 1988, resulting in a radial master cylinder very similar to what we see today.
It was only in 2002, fourteen years later, that the first radial master cylinder would appear on a production motorcycle: the Aprilia RSV 1000. In 2007 Brembo presented the new 19RCS Brembo brake master cylinder, a product bristling with innovative technology.

This radial master cylinder introduced yet another world first. Patented by Brembo and derived from MotoGP, it featured an innovative adjustment system allowing even the most exacting rider to configure the performance of the master cylinder to cater for specific situations.

 

 
 

Up until then, there had been just two aftermarket brake master cylinder choices, with riders having to opt for either a racing product or a road-going component.

Riders using their bikes predominantly on the road generally chose a 19x20 road-going master cylinder, which offers softer, more progressive braking action and a smoother response in less than ideal road conditions.

Those seeking the exhilaration of shaving hundredths of a second from their lap times during track sessions, on the other hand, opted for a 19x18 Racing master cylinder, which delivers strong braking power as soon as the rider touches the lever.

As a guideline, a 19x18 master cylinder is recommended for bikes with calipers fitted with 4 pistons measuring 32/36, 34/34 and 30/34 in diameter, while 19x20 master cylinders are suitable for other calipers.


 
 

Brembo has succeeded in catering for these two seemingly irreconcilable worlds with a single product, which lets the rider switch between configurations with a simple turn of a screwdriver.

The RCS (Ratio Click System) system on the 19RCS Brembo radial brake master cylinder introduces the unprecedented capability to change a fundamental characteristic of the master cylinder, letting the rider adjust the feel of the bike perfectly to their personal preferences.

The system lets the rider adjust the leverage of the brake lever and tailor the characteristics of the braking system to suit different situations, such as dry or wet road conditions and tarmac with poor or good grip, as well as different riding styles.

The 19 mm master cylinder can be installed on any motorcycle with dual brake discs, and offers the advantages of having two different brake master cylinders to choose from: a 19x18 mm unit offering more progressively controllable braking power in exchange for a slightly longer lever travel; and a 19x20 mm unit, giving the rider a more street bike brake lever feel.


 

​The innovative characteristics of this two-in-one master cylinder let the rider switch between configurations in a matter of seconds, selecting a fulcrum-to-piston distance of 18 or 20 mm by simply turning the adjuster screw on the front of the guide lever by 180° with a screwdriver. The system uses a cam (red when set to 18 mm, black when set to 20 mm), which adjusts the distance between the fulcrum point and the contact point with the master cylinder push rod by 2 millimeters: this changes the distribution of the braking force without altering the performance of the system in terms of pure power.

 

 

The Brembo 19RCS is now joined by the all-new Brembo 19RCS CORSA CORTA brake master cylinder, a product destined to become the new benchmark for motorcycle enthusiasts.


 

Brembo S.p.A. | P.IVA 00222620163

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