Better management of thermal expansion / reduction of deformations

Because the braking surface (plate) can "move" slightly relative to the bell, when the disc heats up, the expansion does not transmit unwanted pressure to the bell or the mount. This reduces the risk of the disc "warping" or developing internal stresses and cracks. 

Longer disc life, less likelihood of vibration or pulsation at the pedal/brake under intense thermal stress conditions

Reduction of rotational weight / unsprung mass

Using ergal/aluminium for the bell rather than solid material (e.g. cast iron) results in a weight saving, particularly in the part that rotates and is not directly supported (unsprung mass). 

Better dynamic response, handling, acceleration, less stress on suspension and surrounding components

Better heat dissipation / thermal capacity

The aluminum bell promotes heat conduction and dispersion away from the braking edge. Furthermore, directional ventilation helps draw cold air inward and expel hot air outward, improving overall heat dissipation. The perforations help break down the thermal insulation and remove gases/films that form under intense friction. 

Less “fading” (loss of brake effectiveness due to heat) in intensive use

Better centering / self-alignment than pads

The small controlled “play” allows the disc to self-center in its fit with respect to the brake body, promoting uniform contact of the pads, reducing vibrations and “knockback” (pushing the pads backwards under impacts). 

Smoother braking, more precise pedal/lever response, less uneven pad wear

Increased resistance to cracking and thermal fatigue

Thanks to the fact that the hot part is “insulated” from the bell, localized thermal stresses are reduced, decreasing the risk of heat cracks or permanent deformations. 

Greater reliability in intensive or competitive use

Anti-vibration effect / improved comfort

The use of different materials (cast iron for the braking area, ergal for the bell) combined with the floating structure can attenuate some high-frequency vibrations. 

Smoother braking feel, less unwanted noise/pulsation