Girodisc 340x30 Front Brake Discs for Subaru WRX STI (2018+)

The Girodisc A1-185 front brake discs, measuring 340 × 30 mm, enhance braking endurance during sustained use on the Subaru WRX STI (2018+). Their cast-iron rotors and aluminum hubs form a floating assembly designed to manage thermal stresses and facilitate rotor replacement due to wear. Sold as a pair, including one left-hand 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 followed.

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 discs or rotors. Their shape and compound must be compatible with the mounting, casting, and intended use; follow the specific requirements for this part number and perform the prescribed break-in procedure.

Specifications for Girodisc A1-185 discs for compatible vehicles

• Brand: Girodisc
• PartNumber: A1-185
• Position: front
• Sizes (diameter × thickness): 340 × 30 mm
• Vehicles and models: Subaru WRX STI (2018+)
• Braking surface material: 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: D1-185. Verify compatibility with the caliper generation before replacement.
• Internal ventilation: directional curved fins
• Minimum thickness: 28 mm
• Overall height: 52.7 mm
• Original rotor diameter: 340 mm
• Manufacturing of main components: United States

Vehicles compatible with Girodisc part number A1-185

• Subaru WRX STI (2018+)

• Subaru WRX STI (2018+): Rear pad brackets must be adapted.

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

Girodisc A1-185 Mounting Requirements

• Subaru WRX STI (2018+): Rear brake pad brackets must be modified.

Brake Pads and Brake Systems for Compatible Vehicles

Choose brake pads whose shape is compatible with the calipers, track, and/or the A1-185 rotor, 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 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.

Maintenance of the Girodisc mounting on compatible vehicles

Replacing the pads alone 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 with each pad replacement.

FAQ — Girodisc A1-185 for Compatible Vehicles

What are the sizes of the A1-185 discs for my vehicle? The part number shown measures 340 × 30 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 brake pads. Their shape and compound must be compatible with the A1-185 rotor and/or braking surfaces and 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 in 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 rotors, and an instruction manual for installing new tracks on existing rotors. Consult the document that applies to your specific task before you begin.

Key Features of Girodisc A1-185 Bowl Brake Discs

• 340 × 30 mm size for front 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 rotors help reduce unsprung and rotating masses compared to a comparable one-piece cast iron disc.