CP9449 Radi-CAL 4-Piston Caliper Kit

The AP Racing by Essex Radi-CAL Competition Brake Kit provides a high-performance rear braking solution for track-focused vehicles like the G87 M2, G80 M3, and G82 M4. This kit eliminates the parking brake function to save approximately 20 unsprung pounds over the stock setup, significantly improving handling dynamics. At its core are the AP Racing CP9449 Radi-CAL 4-piston calipers, paired with 365x30mm AP Racing J Hook discs featuring 72 vanes. The pistons are precisely sized to ensure seamless integration with the OEM master cylinder and ABS system, maintaining crucial factory functionality. The calipers are constructed with a hard anodized finish, chosen for its superior abrasion resistance and heat tolerance compared to paint or powder coating, which are prone to color shift and chipping under track conditions. Inside, the calipers utilize ventilated, domed-back stainless steel pistons. Stainless steel offers superior thermal barrier properties over aluminum, helping to prevent brake fluid fade on the track. The domed-back design enhances piston stiffness, leading to improved pedal feel and modulation. Anti-knockback springs are also incorporated to mitigate brake pedal drop caused by wheel and bearing deflection during hard cornering, maintaining consistent pedal engagement. Brake pads are not included, allowing the user to select their preferred compound from a wide range of manufacturers that offer the CP3215D42 pad shape. Installation instructions are included, but it's important to note that the product description mentions the car in the photos is equipped with an aftermarket wheel stud kit, which is not included with this brake kit.