The Girodisc A1-322 front brake discs, measuring 400 × 38 mm, improve thermal management during repeated braking on BMW M2, M3, and M4 (G8X) models equipped with carbon-ceramic rotors (2021+). Their cast-iron rotors and aluminum hubs form a floating assembly designed to manage thermal stresses and facilitate rotor replacement due to wear. Sold in pairs, with one left-hand rotor and one right-hand rotor.
These rotors are intended for the front axle of compatible vehicles in the configuration shown below. They retain the compatible caliper mounting; any required spacers and brake pad specifications must be observed.
The curved internal cooling fins channel air through the rotor to dissipate heat during repeated braking. The floating mounting limits 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. Spring washers minimize cold-mounting noise while allowing the necessary compression for the floating mount.
New brake pads must be installed with new rotors or brake discs. Their shape and compound must match the mounting, cast iron, and intended use; follow the specific requirements for 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 track 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.
Each application is subject to its specific brake system configuration, calipers, and any requirements for brake pads or spacers. Please verify these conditions before ordering.
Select brake pads whose shape is compatible with the calipers, track, and/or A1-322 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 the mounting, which is compatible with the original hydraulic system.
Replacing the pads alone helps keep the controlled rotors in good condition. Reusing a rotor 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.
What are the sizes of the A1-322 discs for my vehicle? The part number shown measures 400 × 38 mm and is mounted on the front 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 are shipped with their hubs.
Do I need to replace the brake pads on my vehicle?Yes. Always install new brake pads with new rotors or new braking surfaces. Use a compound suitable for cast iron and your use. Use the original BMW pad shape for cast-iron rotors in carbon-ceramic calipers.
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.
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.
