Noise during braking is one of the most common problems affecting braking systems. Noise, which normally takes the form of a high-pitched whistle, is generated by the vibration of one of more components of the system (disc, calliper and pad) closely linked with other components of the motorcycle that influence the rigidity and damping of the entire system (such as suspension, wheels and tyres).
In addition to the conventional design guidelines for producing a noise-free disc, Brembo has developed an alternative route based on the idea that interrupting the symmetry of the disc by cutting a spoke separates the critical modes of vibration.
A similar pin to the ones already used for floating discs has been added, in order to allow tangential forces still to be transmitted between the two halves of the disc spoke and contribute to the axial rigidity of the disc.
As well as meeting technical requirements, the pin also partially hides the cut in the disc spoke.
Both types of disc used, in fixed configuration but of different design, made a “mooing” sound (so called because of its resemblance to the sound made by a cow) at a frequency of about 1000 Hz. One of the two geometries in particular generated a more intense and easily repeatable noise.
Measurement of the individual modes of vibration of the disc (every disc has its own modes, which can in turn be correlated to an equally individual frequency and a corresponding deformation of the disc) highlighted the existence, at the frequency in question, of two different but linked modes: the latter, by stimulating each other, give rise to the high-intensity noise.
To separate the two critical modes, the geometric symmetry of the disc was interrupted, thus significantly modifying its structural rigidity and damping, without perceptibly altering either its mass or inertia.
The first test conducted on the vehicle, by cutting one of the disc spokes after first verifying its strength, showed evident improvements compared with the original design.
Subsequently, the single pin solution was developed (hence the name “one pin”). As well as delivering an undisputed technical advantage, the pin can also be used as an element of customisation by the customer.