The Mercedes-Benz A45S AMG (W177) is the definitive hyper-hatch, extracting over 415 hp from its 2.0L engine. However, with the powertrain mass concentrated over the front axle, the factory braking system is under immense thermal load during spirited track sessions or fast canyon runs, leading to heat-soak and Brake Fade.
The Struggle
Managing the kinetic energy of a 1,600 kg (≈ 3,527 lb) compact car with supercar levels of acceleration creates significant engineering hurdles for traditional iron systems:
- Front-End Bias: The A45S performs over 75% of its braking at the front corners, causing iron rotors to reach their heat-sink capacity rapidly.
- Unsprung Mass: Standard 19 or 20-inch setups suffer from high rotating inertia, which blunts turn-in response and steering agility.
- Dust Contamination: Aggressive street pads blackened the 20-inch AMG wheels within days and flash-rust after moisture exposure.
Technical Specification
This "Performance-Hybrid" setup maximizes efficiency by placing Carbon-Ceramic (LCCB) technology on the front axle where heat is most critical, while upgrading the rear with High-Carbon steel for balanced durability.
| Vehicle | Mercedes-Benz A45S AMG (W177) |
|---|---|
| Wheel Size | 20-inch Performance Package |
| Front Rotors | StopFlex 350 mm (13.8 in) Carbon-Ceramic |
| Rear Rotors | TTSPORT 330 mm (13.0 in) High-Carbon Steel |
| Weight Saving | ≈ 55% Reduction (Front Corner) |
| Pad Material | StopFlex CCB-Optimized Ceramic Compound |
Compatibility Redline
A rotor-only swap is strictly applicable for vehicles already running OEM fixed multi-piston calipers (such as the AMG 6-pot front). If your A-Class uses floating/sliding calipers, a Full Kit conversion including calipers and brackets is required to manage the CCB friction profile.
Engineering & Surface Treatment
1. Proprietary Bright & Glossy Coating
Unlike standard carbon ceramic discs that can look dull or porous, StopFlex uses a proprietary ceramic top coat. This ensures the rotor surface remains bright and glossy behind the wheel, prevents oxidation, and ensures zero surface rust, maintaining a premium AMG aesthetic even after washing.
2. Stable Friction Coefficient (**μ**)
Standard iron setups experience friction drop-off as heat builds. StopFlex LCCB rotors maintain a stable 0.44–0.52 μ operating window. Even at extreme temperatures of 900 °C (≈ 1,650 °F), the friction coefficient **μ** remains above 0.40, where iron would suffer catastrophic fade.
3. Front Axle Agility
By shedding ≈5-6 kg (≈ 11-13 lbs) of unsprung mass per front corner, the A45S AMG gains significantly sharper turn-in. This reduction in rotating inertia allows the suspension to track road imperfections faster, improving both mechanical grip and steering "telepathy."
4. 3D Continuous Long-Fiber Skeleton
StopFlex utilizes a 3D Continuous Long-Fiber skeleton with a density of 1.6 g/cm³ and a tensile strength of 140 MPa. This is nearly double the strength of "chopped fiber" OEM discs, ensuring a street service life of up to 300,000 km (≈ 186,000 mi).
Installation Gallery
In-Depth A45S AMG FAQ
Q: Why use CCB in the front and High-Carbon Steel in the rear?
The A45S AMG is front-biased under braking (≈75-80%). Installing LCCB in the front solves 90% of the fade and weight issues. This "Performance-Hybrid" approach is a cost-effective way to achieve massive front-end agility and heat resistance while maintaining the rear axle's cost-efficiency for street driving.
Q: Will these carbon ceramic brakes perform poorly in cold morning traffic?
No. StopFlex C/SiC rotors are designed for immediate Cold Bite. Unlike race-spec carbon brakes, our material provides a stable friction coefficient **μ** from the very first pedal application, making them safe for daily driving and winter conditions.
Q: Can the 350 mm StopFlex kit fit under factory 19-inch wheels?
Yes. While this build uses 20-inch wheels, the 350 mm (13.8 in) rotor is designed to fit most factory 19-inch AMG wheels. However, the fixed 6-piston caliper requires adequate spoke clearance; we recommend verifying the wheel's internal barrel profile.
Q: What is the maintenance benefit of the proprietary coating?
Traditional CCB rotors can develop a "dry" or dull look over time. StopFlex's proprietary coating keeps the surface sealed and bright. This not only looks better but also makes cleaning brake dust (which is already minimal) even easier as it cannot bond to the glossy surface.
Q: Do these rotors require a "bedding-in" procedure?
Yes. To achieve maximum service life and a silent operation, a thermal bedding cycle is required to transfer a thin layer of pad material onto the rotor surface. This prevents glazing and ensures a stable friction coefficient **μ**.
