The crazy idea of the caliper with radial mounts

1972 - Two-piece aluminium fixed caliper. This was the first bike caliper designed by Brembo, used as OEM equipment on street bikes.

The story of the radial mount caliper began back in the early 90s. Like all revolutionary ideas destined to overturn the traditional way of thinking, it was strewn with a myriad of difficulties, mistrust and minor defeats.

At that time, all motorbikes (including those used in the major racing competitions) were equipped with brake calipers fixed perpendicularly in relation to the fork joint.
It was the most natural solution, the most logical, and also the simplest to implement from the construction viewpoint, especially with traditional forks that just need 2 ears on the cast leg.
For this reason, the axial caliper was the standard model for all motorbikes until the 90s. It just wasn’t possible to imagine anything else. In the keen minds of the Brembo technicians though, the idea of a seemingly revolutionary motorbike brake caliper began to take shape.

The company was actively involved in Formula 1, where radial brake calipers had been introduced on the single-seaters back in 1982, with excellent results.
Thanks to their experience and an awareness of the advantages of the radial system over the axial one, the Brembo men started toying with the idea of adapting the radial connection and applying it in the motorcycling world.

In the early 90s, conscious of how daring the idea actually was, they decided to put off the production of a prototype until they’d shown some technical drawings to the man seen as a true guru in the field of motorbikes, a man of great charisma and experience: the Japanese technical manager of the Honda Racing Team.

Unfortunately, the presentation of the drawings turned out to be a bitter disappointment. After looking through the sheaf of drawings laid before him, the Japanese Honda Racing manager pushed them away with a puzzled, bewildered expression. Not only convinced that the solution was infeasible, he even felt it to be heretic for that period, as if someone had suggested fitting a car steering wheel on a motorbike.
A defeat pronounced by one of the major experts in this field would have put anyone off, and in fact the idea was temporarily set aside in Brembo.

But in truth it was just a pause for reflection.
the Brembo engineers still believed in their revolutionary solution. They were firmly convinced that by exploiting the connection on the fork joint, the radial caliper could stiffen not only the caliper itself but the whole braking system, producing definite improvements in overall performance.
In mechanical terms, radial coupling provides greater stiffness for the caliper which, together with a positioning of the brake pads that’s better defined in relation to the disc, gives the rider improved braking sensitivity. Another advantage of axial fixing is the possibility to easily increase the diameter of the brake disc.

Some years went by but then the idea cropped up again, put forward this time to Aprilia. It was precisely in those years that Aprilia was up against the Japanese giants in the 250cc world championship, and was constantly on the lookout for technical solutions that could give it a head start.

The renewed enthusiasm and new energy lavished on the project took the practical form of new drawings and in-depth testing.
At last, the time was right. Aprilia believed in the project and decided to have its test driver Marcellino Lucchi try out the product during some private trials on the Jerez De la Frontera circuit on 28th February 1998. Lucchi’s verdict was positive, so the new Brembo caliper was then tried out over the next few days by the other Aprilia riders too (Testuya Harada, Loris Capirossi and Valentino Rossi). The tests went on throughout the winter.

At the first race of the 1997 World Championship season, the radial caliper appeared on the Aprilia 250. The new technical solution stirred up some perplexity amongst the staff, and there was no shortage of sceptics in the paddock.

Despite this, the radial caliper proved to be an immediate success.

Even though his bike wasn’t particularly competitive overall, Harada won 3 GPs and fought right to the end for the world title.
From then on, the radial caliper came to be used more and more on the track. All the teams, including Honda, quickly turned to the new, more effective Brembo solution. And, with immense style and elegance, the technical manager of Honda Racing admitted his mistake and apologised to the Brembo technicians for his harsh reaction just a few years earlier.

It was a short step from the track to standard production, and it only took a few years before the radial brake caliper appeared on a street bike. It was 2002, and once again the Noale company showed it was the first to believe in the radial caliper, launching the first street motorbike with this solution: the Aprilia 1000.
The rest is recent history. It’s taken over 10 years to see the full success of this product.

Today, the radial caliper is an indispensable technical solution, not only for the supersport and naked bikes but even for the touring models.