Girodisc 390x32 Rear Brake Discs for Porsche 911 (991) GT3, GT3 RS, and GT2 RS (2013–2019) with CCB

The Girodisc A2-154 rear brake discs, measuring 390 × 32 mm, enhance braking endurance during sustained use on the Porsche 911 (991) GT3, GT3 RS, and GT2 RS models equipped with carbon-ceramic rotors (2013–2019), Porsche 911 (992) GT3 and GT3 RS models with carbon-ceramic rotors (2021+), and the Porsche 718 (982) Cayman GT4 RS with carbon-ceramic rotors (2021+). Their cast-iron tracks and aluminum bowls form a floating assembly designed to handle thermal stresses and facilitate the replacement of tracks subjected to wear. Sold in pairs, with one left and one right disc.

These rotors are intended for the rear axle of compatible vehicles in the configuration listed below. They retain the compatible caliper mounting; any required spacers and brake pad specifications must be followed.

The curved internal cooling fins channel air through the rotor to dissipate heat during repeated braking. The floating mounting minimizes stresses caused by thermal expansion differences between the rotor and the housing and helps the rotor center itself between the brake pads, maintaining consistent contact under heat.

The hub is made of 6061-T6 aluminum. The high-strength steel drive pins are cadmium-plated to resist corrosion. They are secured by Class 12.9 bolts and hardened washers. Spring washers minimize cold-mounting noise while allowing the necessary compression for the floating mount.

New pads must be installed with new rotors or brake tracks. Their shape and compound must match the mounting, cast iron, and intended use; adhere to the specific requirements of this part number and perform the prescribed break-in procedure.

On compatible vehicles originally equipped with carbon-ceramic rotors, this pair provides a conversion solution to high-quality cast-iron rotors. It allows you to remove and store the expensive original carbon-ceramic rotors to preserve them during heavy-duty use, while reusing compatible calipers. Use new brake pads suitable for cast iron and adhere to the pad shapes and any spacers specified by the part number. Replaceable brake pads reduce the cost of replacing braking surfaces in heavy-duty applications and offer a choice of linings to tailor bite and pedal reaction to the intended use.

Specifications for Girodisc A2-154 rotors for compatible vehicles

• Brand: Girodisc
• PartNumber: A2-154
• Position: rear
• Sizes (diameter × thickness): 390 × 32 mm
• Vehicles and models: Porsche 911 (991) GT3, GT3 RS, and GT2 RS with carbon-ceramic rotors (2013–2019); Porsche 911 (992) GT3 and GT3 RS with carbon-ceramic rotors (2021+); Porsche 718 (982) Cayman GT4 RS with carbon-ceramic rotors (2021+)
• Braking surface: high-resistance cast steel
• Packaging: pair of complete rotors, one left and one right with disc bells.
• Housing: 6061-T6 aluminum
• Construction: two-piece floating mounting design
• Catalog part number: D2-154. Verify compatibility with the caliper generation before replacement.
• Internal ventilation: directional curved fins
• Minimum thickness: 30 mm
• Original rotor diameter: 390 mm
• Manufacturing of main components: United States

Vehicles compatible with Girodisc part number A2-154

• Porsche 911 (991) GT3, GT3 RS, and GT2 RS with carbon-ceramic rotors (2013–2019)
• Porsche 911 (992) GT3, GT3 RS with carbon-ceramic rotors (2021+)
• Porsche 718 (982) Cayman GT4 RS with carbon-ceramic rotors (2021+)

• Porsche 911 (991) GT3, GT3 RS, and GT2 RS with carbon-ceramic rotors (2013–2019): For factory PCCB; at the front, use the pad shape designed for cast-iron rotors.
• Porsche 911 (992) GT3, GT3 RS with carbon-ceramic rotors (2021+): For vehicles equipped with factory PCCB rotors.
• Porsche 718 (982) Cayman GT4 RS with carbon-ceramic rotors (2021+): For factory PCCB; at the front, use the pad shape for the cast-iron rotor version.

Each application is subject to its specific brake system configuration, calipers, and any requirements for brake pads or spacers. Please verify these requirements before ordering.

Girodisc A2-154 Mounting Requirements

• Porsche 911 (991) GT3, GT3 RS, and GT2 RS with carbon-ceramic rotors (2013–2019): For factory PCCB; at the front, use the pad shape designed for the cast-iron rotor version.
• Porsche 911 (992) GT3, GT3 RS with carbon-ceramic rotors (2021+): For vehicles equipped with factory PCCB rotors.
• Porsche 718 (982) Cayman GT4 RS with carbon-ceramic rotors (2021+): For factory PCCB; at the front, use the pad shape for the cast-iron rotor version.

Brake Pads and Brake Systems for Compatible Vehicles

Select brake pads whose shape is compatible with the calipers, track, and/or A2-154 rotors, and whose compound is suitable for sport driving or track use. The Endless, pagid Racing, or Ferodo Racing ranges may be considered after verifying the appropriate part number.

For intensive use, we recommend compatible aviation-grade hoses and a high-performance brake fluid that meets the vehicle’s specifications, along with proper bleeding and fluid replacement. This recommendation complements a mounting compatible with the original hydraulic system.

Maintenance of the Girodisc mounting on compatible vehicles

Replacing only the pads helps keep the calipers in good condition. Reusing a caliper for up to three pad replacements is subject to inspection of its condition, its mounting components, and the mounting instructions; this number does not constitute a guaranteed service life. Use a new mounting component each time you replace the pads.

FAQ — Girodisc A2-154 for Compatible Vehicles

What are the sizes of the A2-154 discs for my vehicle? The part number shown measures 390 × 32 mm and is mounted on the rear axle. The diameter alone is not sufficient: also check the brake system type and mounting requirements.

Is the product sold in pairs? Yes. It includes a left and a right disc for the same axle. Both discs come with their disc bells.

Do I need to replace the brake pads on my vehicle?Yes. Always install new brake pads with new rotors or new braking surfaces. Their shape and compound must be compatible with the A2-154 track and/or rotor and with the calipers. Then break in the rotors and pads according to the prescribed procedures.

How do I identify the left and right sides? Girodisc rotors come with a label attached to each rotor: LEFT for the left side and RIGHT for the right side, as viewed from the direction of travel. On a left-hand-drive vehicle, “LEFT” corresponds to the driver’s side and “RIGHT” to the passenger side. Follow these labels and the instructions. On models with curved internal fins, the rolling direction depends on this internal ventilation; the surface grooves alone are not sufficient to determine the side.

How do I break in this mounting on my vehicle? Follow the Girodisc procedure and the brake pad manufacturer’s instructions to build up an even transfer ply. The PDF documents below detail installation and break-in.

PDF Documents for Mounting and Break-in

We have included two PDF documents below: an instruction manual for installing and breaking in the discs, and an instruction manual for installing new tracks on existing bowls. Consult the document that applies to your specific task before you begin.

Key Features of the Girodisc A2-154

• 390 × 32 mm size for rear braking on compatible vehicles.
• 6061-T6 aluminum rotor and floating mount to manage thermal stresses.
• Internal ventilation via curved fins to dissipate heat.
• Replaceable pads to maintain a two-piece mounting.
• Left/right pair identified for mounting.
• Aluminum housings to control the unsprung mass and rotating mass of the conversion kit.