The AP Racing Pro5000R CP9660 has become one of the most useful six-piston caliper platforms for track-focused BMW brake conversions. It combines a motorsport-developed caliper with a widely supported pad shape and can be paired with several disc packages, making it particularly relevant to BMW F8X and E9X M3 builds.
This guide explains the key CP9660 dimensions, the difference between our 356 x 32 mm and 368 x 36 mm BMW conversion routes, pad choice and the fitment checks that matter before ordering.
What is the AP Racing CP9660?
CP9660 is a six-piston AP Racing Pro5000R caliper. In the BMW packages offered by Nineteen72 Performance, the handed pair is based around CP9660-2S4L and CP9660-3S4L calipers. The caliper uses an 18 mm-thick pad in the AP Racing CP3905D54 pad family.
The platform is designed for iron brake discs in the region of 356 to 380 mm diameter and 32 to 36 mm thickness, which is why it works well with both the 356 x 32 mm and larger 368 x 36 mm conversions used on our BMW kits.
CP9660 for BMW F87 M2, F80 M3 and F82/F83 M4
For F8X cars, our configurable AP Racing CP9660 front big brake kit allows a choice between two disc-side packages.
356 x 32 mm Yellow Speed Racing route
The 356 x 32 mm package is the smaller and lighter route. It uses two-piece slotted front discs, aluminium bells, vehicle-specific mounting brackets and braided lines. For many fast-road and track-day cars, it offers a substantial upgrade without moving to the largest disc package available for the caliper.
368 x 36 mm XC3 Engineering BTCC route
The larger option uses 368 x 36 mm floating ex-BTCC rotors with XC3 Engineering F8X aluminium bells and CP9660 carriers. The larger rotor requires its own matching bells and carriers rather than sharing the 356 mm hardware.
Important: the XC3 368 x 36 mm rotors are used motorsport components. Cosmetic condition and remaining service life can vary. The vehicle-specific bells and conversion hardware are separate components of the package.
You can also view the dedicated XC3 AP Racing CP9660 F8X BTCC conversion.
CP9660 for BMW E9X M3
The same caliper platform is also used in our BMW E9X M3 CP9660 BTCC big brake conversion, where XC3 vehicle-specific bells and carriers adapt the 368 x 36 mm rotor package to compatible E9X M3 applications.
As with the F8X XC3 package, any ex-BTCC discs or pads included with the kit are previously used motorsport components and should be treated accordingly.
Choosing brake pads for CP9660
The CP3905D54 pad shape gives access to a broad range of performance compounds. Depending on availability and intended use, options can include ENDLESS, Pagid, Ferodo, EBC Racing, Raybestos and other motorsport compounds.
Do not choose a pad simply because it has the highest friction figure. Road temperature, track temperature, disc compatibility, pedal preference, wear rate and noise all matter. A dedicated track compound can be a poor choice for a car that spends most of its life cold on the road.
356 mm or 368 mm?
The larger disc can provide additional thermal mass and leverage, but it also requires more wheel clearance and uses different mounting hardware. A well-matched 356 mm setup can be entirely appropriate for many cars. The right choice depends on vehicle weight, tyre grip, track duration, cooling and wheel package.
Wheel clearance is mandatory
Wheel diameter alone does not prove that a CP9660 kit will fit. Spoke profile, barrel shape, offset and the exact disc/carrier combination all affect caliper clearance. The 368 mm package requires more radial clearance than the 356 mm package.
Always check wheel-to-caliper clearance before ordering or fitting a large brake conversion.
Build the brake system as a package
A big brake kit should be considered alongside pad compound, brake fluid, cooling, rear brake condition and tyre grip. Browse the AP Racing range, BMW F87 M2 braking, BMW F80 M3 braking and BMW F82/F83 M4 braking collections for compatible supporting parts.
Brake conversions are safety-critical. Professional installation, correct bedding procedure and regular inspection are recommended for any road or track car.
