The Audi RS4 Avant and RS5 Coupe/Sportback (B9 generation) represent the pinnacle of the RennSport brand’s compact executive performance. For owners seeking maximum thermal stability and reduced unsprung mass, the factory carbon ceramic brake (CCB) package is a critical upgrade. Understanding the exact technical specifications of these rotors is essential for maintenance, replacement, and ensuring compatibility across the B9 platform.
Contents
- Key Context
- Structured Analysis
- Practical Checklist
- CTA
- FAQ
- Source Notes
- Professional Disclaimer
Key Context
The B9 generation of the Audi RS4 and RS5 introduced a significant departure in braking architecture compared to the previous B8 chassis. While earlier models often shared components with the Audi R8, the B9 platform uses a specific offset and hat design.
In most global markets, the B9 RS4 and RS5 "Ceramic Brake" package (often identified by factory option codes) applies exclusively to the front axle. The rear axle typically retains high-performance steel discs, even when the front is equipped with 400mm ceramic rotors. This configuration prioritizes heat management where the vehicle's weight bias demands it most during heavy deceleration.
Structured Analysis
1. Front Rotor Dimensions and Construction
The primary specification for the Audi RS4 and RS5 (B9) front carbon ceramic rotor is 400mm in diameter with a 38mm thickness. These rotors are a two-piece design, featuring a carbon-fiber reinforced silicon carbide (C/SiC) friction ring floating on a machined aluminum hat (bell). This floating design allows for radial expansion under extreme heat, preventing the warping commonly associated with steel discs.
2. Weight Comparison vs. Steel Counterparts
A defining characteristic of the B9 CCB rotor is the weight reduction. A standard 375mm RS steel rotor weighs approximately 12.5kg to 13.5kg. In contrast, the larger 400mm carbon ceramic rotor weighs roughly 7.5kg to 8.0kg. This reduction of nearly 5kg per corner significantly improves suspension response and steering feel by lowering the unsprung mass.
3. Caliper Integration and Fitment
The 400mm rotors are paired with a 6-piston fixed monoblock caliper, usually manufactured by Akebono for Audi. Because of the massive diameter of the rotor and the profile of the 6-piston caliper, wheel clearance is a primary concern. Most B9 RS models require a minimum of a 19-inch wheel, though some 19-inch designs may still interfere with the caliper weight or barrel clearance; 20-inch wheels are the standard fitment for CCB-equipped vehicles.
4. Platform-Specific Offset (B9 vs. B8)
It is important to note that B9 rotors are not interchangeable with B8 RS4/RS5 rotors. The B9 chassis utilizes a different hub offset and hat depth. Owners attempting to retrofit or source used parts must ensure the rotors are specifically designated for the B9 chassis (approx. 2017–present) to avoid alignment issues with the caliper carrier.
5. Rear Axle Specifications
While the front uses 400mm ceramic discs, the rear of the B9 RS4 and RS5 typically utilizes a 330mm or 350mm ventilated steel rotor. Currently, there is no factory-offered carbon ceramic rear rotor for the B9 RS4/RS5 platform. Owners looking for a "four-corner" ceramic setup must look to the aftermarket, as Audi's engineering focus for this platform remained on front-axle thermal management.
Practical Checklist
- Minimum Wheel Size: 19-inch (recommended 20-inch for guaranteed barrel clearance).
- Rotor Diameter: 400mm (Front).
- Rotor Thickness: 38mm New / 37mm Service Limit (approximate).
- Torque Specs: Ensure hat-to-hub mounting bolts are torqued to factory RS specifications (typically 120Nm to 140Nm depending on bolt type).
- Pad Compatibility: Only use pads specifically formulated for ceramic friction surfaces; steel-rotor pads will destroy the ceramic coating.
- Visual Inspection: Check for "oxidization" (a darkened, rough texture) or "pitting" rather than just thickness, as CCB rotors wear by losing mass rather than width.
Recommended Next Step
Looking to plan the right brake package for Audi RS4? Browse our Audi Collection to compare vehicle-specific carbon ceramic rotor and upgrade options.
FAQ
Can I install B9 CCB rotors on an Audi S5?
While the hub bolt pattern is the same (5x112), you would need the RS-specific 6-piston calipers, carriers, and potentially modified brake lines and master cylinder coding to ensure proper bias and clearance.
How long do the B9 RS4/RS5 ceramic rotors last?
Under street driving, they can last over 100,000 miles. However, heavy track use significantly accelerates carbon oxidation. They should be weighed to determine their remaining service life.
Why is my rear brake rotor still steel?
Audi designed the B9 RS platform with a front-biased CCB package to balance cost and performance. The front brakes perform the vast majority of the work, and the rear steel rotors are sufficient for the vehicle’s weight distribution.
Are the rotors directional?
Yes. Carbon ceramic rotors feature internal cooling vanes designed to pull air from the center and exhaust it outwards. They are side-specific (Left and Right).
Explore fitment-focused options here: Audi Collection.
Source Notes
- Source: https://en.wikipedia.org/wiki/Audi_RS_4
- Source: https://forums.audirevolution.net/t/new-carbon-ceramic-brake-disc-option/17028
Professional Disclaimer
All third-party trademarks, brand names, and model names are the property of their respective owners. References are for identification only and do not imply affiliation or endorsement. Carbon ceramic brake components are safety-critical; all installations and specifications should be verified by a certified technician according to the official vehicle service manual.