Brakes

Quick Summary

Carbon ceramic brakes produce different sounds than iron brakes, and understanding which noises are normal versus which warrant investigation is essential knowledge for every owner. The higher stiffness and lower damping of the C/SiC composite, combined with the hard SiC surface coating on AME Motorsport's CCB rotors, create a unique acoustic signature that includes cold morning squeal, low-speed hiss, occasional clicking, and other sounds that are entirely benign. This guide from AME Motorsport covers every noise type you may encounter, explains the physics behind each one, and provides clear diagnostic guidance so you can distinguish routine sounds from genuine concerns. The Technology for Everyone philosophy means equipping owners with the knowledge to maintain confidence in their braking system.

Understanding Why Carbon Ceramic Brakes Sound Different

Before examining specific noise types, it helps to understand why carbon ceramic brakes produce different sounds than conventional iron systems. Every disc brake system is a vibrating mechanical assembly. When the pad contacts the rotor, friction forces create microscopic vibrations at the interface. These vibrations propagate through the rotor, caliper, and suspension components, and some fall within the audible frequency range.

The frequency, amplitude, and character of these vibrations depend on material properties. Carbon ceramic (C/SiC) is significantly stiffer than cast iron, so it vibrates at higher frequencies, producing higher-pitched sounds. Cast iron naturally damps vibrations well, absorbing energy within its microstructure, while carbon ceramic composites have lower damping characteristics, meaning vibrations persist longer and are more readily transmitted as audible sound. The SiC coating on AME Motorsport's CCB rotors creates a hard-on-hard contact with the brake pad compound, generating different vibration modes than the softer contact of pads on iron. Additionally, carbon ceramic's very low coefficient of thermal expansion means components expand and contract at different rates relative to metallic caliper and hub components, creating relative movement that can produce sounds.

These material differences mean that a perfectly functioning carbon ceramic brake system will produce sounds that an iron brake system would not, and vice versa. This is not a defect. It is a direct consequence of fundamentally different materials interacting at the friction interface. For a broader overview of the technology, see the complete guide to carbon ceramic brakes.

The Role of Temperature

Temperature profoundly affects carbon ceramic brake noise. Most normal sounds occur when the brakes are cold and diminish or disappear as the system reaches operating temperature. Pad compounds are formulated to work optimally within a specific temperature range, and below that range the friction characteristics change, generating more vibration. Thermal expansion closes small gaps between components as the system warms up, eliminating sources of rattling or clicking. Moisture from dew or condensation on cold rotors creates temporary friction changes that disappear once the surface dries.

Type 1: Cold Morning Squeal

What It Sounds Like

A high-pitched squeal or screech during the first few brake applications of the day, particularly on cold mornings. It can be quite loud and attention-getting, typically lasting for the first two to five brake applications before diminishing significantly or disappearing entirely.

Why It Happens

Cold morning squeal is the most common carbon ceramic brake noise and is completely normal. Overnight condensation or morning dew creates a thin film of water on the rotor friction surface. When the pad first contacts this wet surface, the water briefly alters the friction coefficient, creating conditions for high-frequency vibration. Meanwhile, the brake pad compound sits below its optimal temperature range, making it stiffer and less conformal. The harder, cooler compound concentrates contact pressure at high points on the rotor surface, generating vibration. The first few stops also create localised heating at the pad-rotor interface while the rest of the system remains cold, and this temperature gradient contributes to differential expansion and vibration.

This noise is normal when it occurs on the first two to five applications, disappears after warm-up, is more pronounced in cold or humid weather, and does not affect braking performance or produce pedal vibration. Investigate if squeal persists after ten or more minutes of driving, is accompanied by pedal vibration, is intensifying over time, or is significantly louder at one corner than the others. For more on cold-start characteristics, see the carbon ceramic brake squeak guide.

Type 2: Light Hiss or Swish at Low Speed

What It Sounds Like

A gentle hissing, swishing, or light brushing sound audible at low speeds, typically below 30 km/h, when the brakes are not applied. It sounds like continuous, very light contact between pad and rotor.

Why It Happens

In all disc brake systems, the brake pads sit very close to the rotor surface even when the brakes are not applied. With iron rotors, very light pad-rotor contact produces minimal sound because the softer iron surface absorbs the vibration. With the hard SiC surface of carbon ceramic rotors, even the lightest contact produces a faint sound that becomes audible in quiet environments such as parking garages, residential streets, and drive-throughs. At higher speeds, road noise, wind noise, and tyre noise mask this gentle sound completely.

This noise is normal when it occurs at low speeds only, disappears or becomes inaudible above 30 to 40 km/h, is consistent and unchanging in character, and has no effect on braking performance. Investigate if the sound is harsh rather than gentle, changes in character or intensity over time, or has a rhythmic pattern corresponding to wheel rotation that could indicate rotor runout or uneven pad contact.

Type 3: Grinding

What It Sounds Like

A harsh, grating, metallic grinding sound during braking. This is distinctly different from the light hiss described above. Grinding is aggressive, rough, and immediately noticeable, and may be continuous during braking or intermittent.

Why It Happens

Unlike the previous two sounds, grinding is potentially a concern and warrants investigation. The most likely cause is the pad wear indicator contacting the rotor surface, a small metal tab designed to make a scraping noise when the pad friction material has worn to its minimum thickness. Other causes include small stones, grit, or road debris trapped between the pad and rotor, pad contamination from oil, grease, or road chemicals that alter friction characteristics, and glazed pad surfaces from overheating without proper bedding that create a hardened layer interacting poorly with the rotor.

Brief, one-time grinding that does not repeat is likely debris passing through and being expelled, which is normal. Very light grinding in the first few stops after driving through gravel or construction zones is also expected. Investigate consistent, repeatable grinding during braking, grinding that increases with pedal pressure, grinding accompanied by reduced braking performance, and grinding that persists beyond a few brake applications.

What to Do About Grinding

First, check pad thickness, as this is the most likely cause. If pads are at or near their wear indicator, replace them immediately with a compound designed for carbon ceramic rotors. Second, inspect for debris trapped between the pad and rotor. Third, examine pad surfaces for contamination, glazing, or uneven wear. Fourth, inspect rotor surfaces for scoring, embedded material, or surface damage. For pad selection guidance, see best brake pads for carbon ceramic rotors.

Type 4: Clicking or Ticking

What It Sounds Like

A rhythmic clicking, ticking, or light tapping sound that corresponds to wheel rotation. It may be present during braking, while rolling freely, or both, and the click rate changes with vehicle speed.

Why It Happens

Clicking sounds from carbon ceramic brakes are almost always related to thermal expansion and are completely normal. Carbon ceramic rotors have a very low coefficient of thermal expansion compared to the metallic components they mount to, including aluminium or cast iron hubs and steel mounting hardware. As the system heats up during driving, these different materials expand at different rates, and the relative movement between components produces clicking or ticking, particularly at the rotor-to-bell interface.

Caliper mounting hardware, pad retaining springs, and anti-rattle clips can also produce clicking as they shift slightly during thermal expansion and contraction. This occurs with both iron and carbon ceramic brakes, but it is more audible with carbon ceramic due to the system's lower overall noise floor. Brake pads also have a small amount of designed clearance within the caliper bracket to allow for thermal expansion, and as the vehicle accelerates, brakes, or traverses bumps, pads can shift within this clearance and produce a light click.

This noise is normal when it corresponds to thermal changes, matches wheel rotation speed, has no effect on braking performance, and is consistent. Investigate clicking that is very loud or getting louder, is accompanied by brake drag or uneven braking, occurs at the same point in every wheel rotation, or starts suddenly after a service event.

Type 5: Deep Vibration or Hum

What It Sounds Like

A low-frequency humming, droning, or vibration felt as much as heard. It typically occurs during braking and may be accompanied by pulsation through the brake pedal. The sound has a deep, resonant quality that is distinctly different from high-pitched squeal.

Why It Happens

Deep vibration during braking is the noise type most likely to indicate a genuine issue. Rotor surface irregularity from thickness variation, localised pad deposit buildup, or thermal effects causes the pad to ride over variations during braking, creating low-frequency vibration transmitted through the caliper and suspension. Disc Thickness Variation (DTV) is often caused not by physical warping but by uneven transfer of pad material onto the rotor surface. Carbon ceramic rotors are extremely resistant to actual warping due to their very low thermal expansion. Improper or incomplete bedding is another common cause, leaving the pad transfer layer uneven.

Very mild vibration under specific conditions that does not affect stopping performance may be within acceptable limits, but any noticeable pedal pulsation during normal braking, worsening vibration, vibration accompanied by steering wheel shake (front rotor issue), vibration felt through the seat (rear rotor issue), or vibration that appeared after a specific event warrants investigation. The first corrective action should always be re-bedding the brakes using AME Motorsport's recommended bedding procedure, as many vibration issues resolve by redistributing the pad transfer layer. If this does not resolve the vibration, inspect pads and check rotor runout with a dial indicator.

How Brake Pad Compound Affects Noise

The brake pad compound is the single most controllable factor affecting carbon ceramic brake noise. Pads specifically formulated for carbon ceramic rotors are engineered to minimise noise, vibration, and harshness while delivering appropriate friction characteristics. These purpose-designed compounds address surface conformity at various temperatures, transfer layer characteristics that affect friction consistency and noise, internal damping that absorbs vibration before it propagates to the caliper, and operating temperature range optimisation.

Using pads designed for iron rotors on carbon ceramic surfaces is a common cause of excessive noise and should always be avoided. AME Motorsport tests its CCB rotors with recommended pad compounds to ensure the friction couple delivers optimal NVH performance across the complete temperature range.

The Importance of Proper Bedding

Even the best pad compound will produce excessive noise if not properly bedded. The bedding procedure establishes a thin, even deposit of pad material on the rotor surface that is essential for consistent friction and low noise. An improperly bedded system may exhibit squeal at all temperatures, inconsistent friction with a grabby or spongy feel, vibration from uneven pad deposits, and accelerated wear on both pads and rotor coating.

CCB vs CCM: Noise Differences

AME Motorsport's two product lines have different noise characteristics due to their surface engineering differences. CCB and CCM serve different applications.

The CCB (SiC Coated) line, designed for combined street and track use, produces slightly higher-pitched sounds during cold operation due to the hard-on-hard pad-rotor interface. Once at operating temperature, the SiC surface promotes even pad deposit formation, generating less noise. The coating surface is smoother and more uniform than uncoated C/SiC, reducing low-speed swishing. Overall, CCB rotors have more predictable and consistent noise characteristics throughout their service life.

The CCM (Uncoated) line, designed for dedicated track applications, has different friction characteristics at low temperatures that can produce different cold noise profiles. CCM rotors may produce more initial noise during the first few track sessions as the surface breaks in, but they reach optimal operating characteristics more quickly under aggressive track braking and are more tolerant of aggressive high-temperature pad compounds. For track-focused applications, noise is generally a lower priority than outright performance.

Noise Reduction Strategies

While many carbon ceramic brake noises are normal, several steps can minimise noise within the system's inherent characteristics. Proper bedding is the most effective strategy: follow AME Motorsport's recommended procedure precisely after any pad change or new rotor installation. Correct pad selection using compounds specifically designed for carbon ceramic rotors is critical. Caliper hardware maintenance ensures all retaining clips, anti-rattle springs, and guide pin boots are in good condition. Avoiding contamination by keeping rotor and pad surfaces free from oil, grease, and chemical residue prevents altered friction characteristics. And in cold conditions, a brief warm-up routine applying the brakes gently several times during the first few minutes of driving brings the system to temperature gradually, minimising cold squeal duration.

AME Motorsport offers carbon ceramic solutions for a wide range of vehicles, from the Porsche 992 GT3 and BMW M2/M3/M4 F/G Series to the Mercedes-AMG G63 and Lamborghini Huracan. Every application uses long fibre C/SiC construction, and CCB products feature the SiC coating exceeding 0.8mm that delivers five times wear resistance and predictable acoustic behaviour.

Recommended Brake Pads for Carbon Ceramic Rotors

When upgrading to carbon ceramic rotors, selecting the correct brake pad compound is essential. Standard metallic pads must never be used on carbon ceramic surfaces. AME Motorsport recommends these proven carbon ceramic compatible compounds:

• Pagid RSC Series — European racing heritage, three compounds (RSC1 street, RSC2 endurance, RSC3 sprint) covering every driving scenario
• Barbaro Racing — Italian motorsport lineage with compounds from whisper-quiet C-01 to RS-635 competition
• NetzschRacing — German precision engineering with Street, Race, and Carbon Ceramic Series
• Schaffen ZZ Racing — Asian touring car championship pedigree, validated in extreme heat and humidity

For detailed compound comparisons: Best Brake Pads for Carbon Ceramic Rotors

Frequently Asked Questions

Is it normal for carbon ceramic brakes to squeal when cold?

Yes. Cold morning squeal is the most common carbon ceramic brake noise and is completely normal. It occurs due to moisture on the rotor surface, cold pad compound stiffness, and thermal differentials across the system. The squeal typically disappears after two to five brake applications as the system warms up. It is more pronounced in cold and humid conditions and has no effect on braking performance. AME Motorsport's SiC-coated CCB rotors are engineered to minimise this effect through surface characteristics that promote consistent pad contact even at low temperatures.

Why do my carbon ceramic brakes make a hissing sound at low speed?

The light hiss or swish audible at low speeds is caused by minimal pad-to-rotor contact as the wheel rotates. The hard SiC surface of carbon ceramic rotors makes this light contact more audible than it would be with softer iron rotors. This sound is normal, does not indicate a problem, and is completely masked by road and wind noise at driving speeds above 30 to 40 km/h.

Should I be worried about grinding noise from my carbon ceramic brakes?

Grinding warrants investigation. The most common cause is brake pads reaching their wear indicator, so check pad thickness immediately. Other causes include trapped debris between the pad and rotor, pad contamination, or glazed pad surfaces from overheating. Brief, one-time grinding that does not repeat is likely debris passing through. Consistent, repeatable grinding during braking requires prompt attention. Replace worn pads with compounds specifically designed for carbon ceramic rotors.

Can the wrong brake pads cause carbon ceramic brake noise?

Yes. Using brake pads not designed for carbon ceramic rotors is one of the most common causes of excessive noise. Pads formulated for iron rotors have different friction characteristics, transfer layer properties, and damping qualities that are not optimised for the SiC surface of carbon ceramic rotors. Always use pads specifically designed and tested for carbon ceramic applications to ensure optimal NVH performance.

Will re-bedding my brakes fix noise issues?

Re-bedding can resolve noise caused by uneven pad deposits on the rotor surface, which is common after aggressive driving, incomplete initial bedding, or pad changes. Follow AME Motorsport's recommended bedding procedure precisely. If noise persists after proper re-bedding, the cause may be mechanical, such as worn pads, debris, or hardware issues, rather than surface-related.

How do CCB and CCM rotors differ in noise characteristics?

CCB (SiC coated) rotors generally have more predictable and consistent noise characteristics over their lifespan because the SiC coating provides a stable, uniform friction surface. CCM (uncoated) rotors may exhibit different noise profiles, particularly during initial break-in on track. CCB is designed for street and track use where noise is a consideration, while CCM is track-focused where maximum performance takes priority over acoustic refinement. Learn more in our CCB vs CCM Explained article.

My carbon ceramic brakes vibrate during braking. Is the rotor warped?

Carbon ceramic rotors are extremely resistant to warping due to their very low coefficient of thermal expansion. What feels like warping is almost always Disc Thickness Variation caused by uneven pad material deposits on the rotor surface, not physical distortion of the rotor itself. Re-bedding the brakes following the recommended procedure often resolves this. If vibration persists after re-bedding and pad inspection, have the rotor runout and thickness variation measured by a specialist familiar with carbon ceramic brake systems.

Do carbon ceramic brakes make more noise than iron brakes?

Carbon ceramic brakes produce different sounds rather than necessarily more noise. The most noticeable difference is cold morning squeal, which is more common and pronounced with carbon ceramic than with iron. At normal operating temperature, properly bedded carbon ceramic brakes with appropriate pads are generally quiet. The perception of increased noise often comes from unfamiliarity with carbon ceramic's different acoustic characteristics. Most owners report that after a few weeks of ownership, the sounds become predictable and unremarkable.