GiroDisc A1-307 2-Piece Floating Front Rotors for Toyota GR Supra/BMW 348mm

Vehicle Fitment

• 2020-2026 Toyota GR Supra (A90, 3.0L I6)
• 2019-2026 BMW M340i Sedan / Touring (G20/G21, 3.0L I6)
• 2021-2026 BMW M440i Coupe / Convertible / Gran Coupe (G22/G23/G26, 3.0L I6)
• 2018-2026 BMW X3 M40i (G01, 3.0L I6)
• 2019-2026 BMW X4 M40i (G02, 3.0L I6)
• 2019-2026 BMW Z4 M40i (G29, 3.0L I6)
• BMW G-chassis models equipped with optional M Sport brakes (348mm front rotor)

Fitment Notes

• Fits all BMW G-chassis applications with a 348mm OEM front rotor -- not limited to models listed above
• Verify OEM front rotor diameter is 348mm before ordering on non-listed G-chassis models
• Compatible with OEM calipers -- no caliper upgrade required
• Replacement rings sold separately: GiroDisc D1-307
• Companion rear rotor set: GiroDisc A2-307
• OEM BMW reference: 34116860911 (left) / 34116860912 (right)

Features

• 2-piece fully floating rotor design
• 72 curved vane centrifugal cooling design
• 6061-T6 aircraft-spec aluminum hat, black anodized
• Proprietary high-carbon iron rotor ring
• Cadmium-plated high-strength steel drive pins
• Spring clips and Belleville washers for street-friendly float
• Reusable hat -- only rings need replacement
• Direct bolt-on, no modifications required
• Manufactured in USA from US-sourced materials

Specifications

• Position: Front
• Rotor diameter: 348mm
• Minimum replacement thickness: 34mm
• Hat material: 6061-T6 aluminum, black anodized
• Ring material: Proprietary high-carbon cast iron
• Drive pins: High-strength steel alloy, cadmium-plated
• Weight savings: Approx. 2 kg per rotor vs. OEM
• Vane count: 72 curved vanes

Included Components

• 2x 2-piece floating front brake rotors (assembled)
• 2x Sets of drive pins with spring clips and Belleville washers

Product Description

The GiroDisc A1-307 is a 2-piece fully floating front brake rotor set engineered for the Toyota GR Supra (A90) and BMW G-chassis models equipped with a 348mm front rotor. Each rotor consists of a reusable 6061-T6 aluminum hat joined to a proprietary high-carbon iron ring via cadmium-plated drive pins, Belleville washers, and spring clips -- providing race-proven axial float that eliminates the hot spots and warping common with solid 1-piece rotors. The 72 curved vanes function as a centrifugal pump, drawing cooling air through the rotor under hard use to dramatically reduce thermal fade on track.

Weighing approximately 2 kg less per corner than the OEM unit, the A1-307 reduces both unsprung and rotating mass, improving acceleration response and suspension feel without any sacrifice to ABS efficiency or brake bias. Installation is direct bolt-on with no modifications required, and the system works with stock calipers. When the rings reach minimum thickness (34mm), only the rings (D1-307) need to be replaced -- the aluminum hat is reused. All components are designed, cast, machined, and assembled in-house at GiroDisc's facility in Bellingham, WA using domestically sourced materials. Sold as a pair.