A1-156SL – GiroDisc 2-Piece Rotor Assembly; Left

Girodisc is an American manufacturer of two-piece floating brake rotors founded and based in the United States. The company specialises in high-performance replacement rotor systems designed as direct-fit upgrades to OEM or aftermarket brake calipers, without requiring a complete big brake kit conversion.

Their rotors use an aluminium hat (bell) paired with a separate iron rotor ring, with the two components connected via floating bobbins. This floating design allows the ring to expand thermally without transferring stress to the hat, reducing warping and cracking under sustained track use. The lighter aluminium hat also reduces unsprung weight compared to a solid OEM rotor.

Girodisc rotors are widely used in endurance racing, time attack, and serious track day driving where repeated hard braking cycles generate heat that OEM solid rotors cannot manage reliably. They are a popular choice for drivers who want the thermal performance of a motorsport rotor in a package that bolts directly to their existing caliper.