How a Carbon-Ceramic Conversion Works on Factory Calipers

The starting point

The owner wanted carbon-ceramic brakes but not new calipers. The GranTurismo S has 6-piston calipers on the front and 4-piston calipers on the rear. Both are good calipers, and keeping them keeps the factory hydraulics, pedal ratio and piston areas.

A few years earlier he had fitted two-piece iron rotors. At the front, caliper spacers moved the calipers outward so a 380 mm rotor could replace the 350 mm original. The rear stayed at the factory 330 mm.

Sizing and brake balance

We specified 380 × 32 mm carbon-ceramic rotors for the front and 355 × 28 mm for the rear. Each decision follows from the caliper.

Thickness stays at factory size

Rotor thickness sets where the pads sit and how far the pistons travel. Keeping 32 mm front and 28 mm rear means the factory calipers work within their designed piston stroke and the pads seat squarely. Only the diameter changes.

Larger diameter needs a radial spacer

A fixed caliper has to follow the outer edge of the rotor. The spacer moves it outward by half the diameter increase:

• Front: (380 − 350) ÷ 2 = 15 mm
• Rear: (355 − 330) ÷ 2 = 12.5 mm

The front diameter is unchanged from the iron upgrade, and the owner’s wheels already cleared it. The rear is new, so its spacer and wheel clearance were checked in a test fit before installation.

More brake torque for the same pedal pressure

For each rotor face, brake torque is:

T = μ × p × A × r_eff

μ is pad friction, p line pressure, A total piston area on that side, and r_eff the effective radius: roughly the rotor radius minus half the pad’s radial height h. The pistons and hydraulics are unchanged, so clamp force at a given pedal pressure is unchanged. Torque grows in proportion to r_eff.

The spacer moves the pad outward by exactly the offset above, so:

Swept area per face is 2π × mean radius × h. With pad height fixed by the caliper, it grows by the same proportion as the effective radius. The result holds across 40–60 mm pad heights, so the exact pad dimension is not needed.

Why the rear grows too: brake balance

The earlier iron upgrade added about 10% torque at the front and none at the rear, which shifted braking toward the front axle. The 355 mm rear adds about 9%, restoring the balance:

Front-to-rear torque ratio versus factory:
Iron upgrade: 1.10 ÷ 1.00 = +10% toward the front
CCB kit: 1.10 ÷ 1.09 ≈ +1%, close to the factory balance

These ratios assume pad friction changes by the same factor on both axles. Pad compound, tyre grip and weight transfer still govern the final result on the road.

Heat

The energy of a stop is set by the car’s mass and speed, not by the brakes. With balance unchanged, each axle absorbs its usual share, spread over about 9–10% more swept area. That is roughly 8–9% less energy per square centimetre of friction surface.

Carbon-ceramic stores less heat than iron because a ring of the same size weighs far less, so it runs hotter. It is designed to: silicon carbide keeps its strength and friction at temperatures where iron fades and distorts. The larger diameter adds swept area and exposed ring surface to shed that heat into the airflow.

Rotor construction

Each rotor is a two-piece assembly with three parts, and none of them contains iron:

• Friction ring: long-fibre carbon-ceramic (C/SiC), with a silicon carbide coated friction surface.
• Centre bell (hat): 7075-T6 aluminium alloy with a black finish.
• Ring screws: Grade 5 titanium, Ti-6Al-4V.

Rust is iron oxide. Carbon-ceramic, aluminium and titanium contain no iron. Stainless steel does, which is why stainless hardware can still stain in road salt.

Titanium screws

We weighed complete screws: 0.029 kg for titanium against 0.048 kg for stainless steel, 39.6% lighter. The kit uses 40 screws, 10 per rotor:

40 × (0.048 − 0.029) kg = 0.76 kg, about 0.8 kg (1.7 lb) across all four rotors.

That mass is both unsprung and rotating, but weight is not the main reason to use titanium. Grade 5 titanium is stronger than common stainless screws and highly resistant to corrosion. With a carbon-ceramic ring and an aluminium hat, it makes a rotor with no corroded ring, no corroded hat and no rusted hardware.

Titanium and aluminium are a galvanic pair. Keep the screws at their specified torque and inspect the hat seats at each pad change, especially in winter-salt climates.

Test fit and installation

The kit

• 2 × 380 × 32 mm front two-piece rotors, ring fixed to the hat with screws
• 2 × 355 × 28 mm rear two-piece rotors, ring fixed to the hat with screws
• 1 set of CCB-compatible street pads for both axles, with new wear-sensor wires and stainless steel noise-reduction shims
• Caliper spacers for the front and rear axles

Carbon-ceramic needs its own pads. Pads made for iron rotors are formulated for a different friction surface and can wear the silicon carbide layer. The shims damp pad vibration to reduce squeal.

The finished kit before shipping.

Test fit

Before final installation, the owner mounted the rotors and calipers and filmed each corner. A test fit confirms three things: pad alignment on the friction ring, clearance between the hat and the caliper body, and clearance between the caliper and the wheel. The rear 355 mm rotor needed the most careful check because it is a new size on that axle.

The owner’s test-fit video.

Installed

With clearance confirmed, the kit went on as a bolt-on installation: no changes to the calipers, hubs or brake lines.

The installed kit behind the wheels.

What changes

• Lower unsprung and rotating mass. Carbon-ceramic is about one-third the density of cast iron, and the titanium screws save a further 0.8 kg. Lower unsprung mass helps the dampers keep the tyres in contact over bumps. This car already had two-piece iron rotors, so most of the saving here comes from the rings.
• Consistent braking under heat. Repeated hard stops fade far less. A single emergency stop is limited by the tyres, so the gain is in how the brakes behave on the fifth stop, not the first.
• Brake balance close to factory, with about 10% more torque at the front and 9% at the rear for the same pedal pressure.
• Very little brake dust. The dust carbon-ceramic produces is not iron-based, so it does not bake onto wheels as rust-coloured deposits.
• No corrosion. No rust bloom on the rings after rain or washing, and no corroded hats or hardware.
• Appearance. Larger rotors fill large-diameter wheels, and the grey ring, black hat and titanium screws suit a car with red calipers.

Things to know

• Bed in the pads before hard use, following the supplied procedure.
• Use CCB-compatible pads only.
• Carbon-ceramic is hard but can chip if struck on the edge. Take care when removing or fitting wheels.
• A larger rotor needs wheel clearance. Check spoke and barrel clearance, as the owner did with his test fit.

Going further: magnesium wheels

The wheel and tyre are the largest unsprung and rotating mass at each corner. As a wheel manufacturer within Forza Performance Group, we also make forged magnesium custom wheels. Magnesium has about two-thirds the density of aluminium (≈ 1.8 against 2.7 g/cm³).

Combined as one corner package:

• Forged magnesium custom wheels with titanium lug nuts
• Carbon-ceramic rotors with Ti-6Al-4V screws and 7075-T6 hats

Cutting mass from wheel, lug nuts and rotor together sharpens steering response and damping control more than any one change alone. Ask about wheels when you send your vehicle details.

Plan a conversion for your car

Send us:

• Make, model, year and factory brake option.
• Current rotor sizes front and rear, and details of any earlier brake upgrade.
• Photos of each caliper and rotor, and your wheel size and offset.

Email forzaccb@forzaaa.com. We’ll confirm the sizes, spacers and pads for your car.

No fitment data for your rotors? Our reverse engineering guide shows how to measure them. GranTurismo owners can start from our GranTurismo M145 (2011–2019) rotors.