For the Bentley Continental GT and GTC (First and Second Generation), the part numbers 3W0615301T (Left) and 3W0615302J (Right) refer to the massive 420mm Carbon Ceramic front brake discs. These are the largest brakes fitted to a production passenger car of their era and are a hallmark of the “Speed” and “Supersports” models.

1. Technical Specifications

Carbon ceramic brakes (CSIC) offer significant advantages over standard iron discs, particularly for a vehicle as heavy as a Bentley.

• Material: Carbon Fiber Reinforced Silicon Carbide.

• Diameter: $420\text{ mm}$ (Front).

• Thickness: $40\text{ mm}$ (New) with a wear limit typically around $39.4\text{ mm}$.

• Weight Saving: Approximately 20 kg (44 lbs) of unsprung mass is saved compared to the equivalent iron system, significantly improving steering response and suspension damping.

• Operating Temp: Virtually immune to “brake fade.” They perform best once they have some heat in them, making them ideal for high-speed continental cruising.

2. Part Number Identification

• 3W0615301T: Front Left Disc.

• 3W0615302J: Front Right Disc.

• Note on Directionality: These discs are directional. The internal cooling vanes are curved to pull air through the disc. Installing them on the wrong side will lead to overheating and potential disc failure.

3. Wear & Inspection (Important)

Unlike iron discs, you cannot measure carbon ceramic wear by thickness alone.

• Visual Inspection: Look for “pitting” or small dark spots on the surface. If the surface feels “rough” like 100-grit sandpaper rather than smooth glass, the carbon fibers are oxidizing.

• Weight Method: Each disc has a minimum weight stamped on the aluminum center hat (e.g., “Min Weight 7250g”). If the disc weighs less than this, it must be replaced, even if it looks perfect.

• Damage: Ceramic is brittle. A single stone chip or a mechanic accidentally hitting the disc with a wheel rim during a tire change can cause a crack that requires the entire disc to be scrapped.

5. Pad Compatibility

Warning: You must use specific ceramic-compatible brake pads (typically part number 3W0698151AL or similar). Using standard iron-disc pads will destroy the ceramic surface of the discs within a few hundred miles.