AP Racing Radi-CAL Competition Rear Kit 355mm - C8 Corvette Z51

The AP Racing by Essex Radi-CAL Competition Brake Kit is a rear brake upgrade for the 2020-2025 C8 Corvette Stingray with Z51. It pairs AP Racing CP9661 Radi-CAL Pro5000R racing six-piston calipers with 355 x 32mm, 72-vane AP Racing J Hook discs on fully floating aluminum hats, built for track days and competition driving. Clears Z51 OEM 20 inch Trident rear wheels without a spacer.

Why upgrade

The kit removes about 12 lb of unsprung weight from the rear of the car compared with the OEM Z51 brakes, despite more pistons and larger discs. Each caliper weighs 6.2 lb without pads, against 7.0 lb for the factory 4-piston opposed caliper. Each two-piece disc weighs 17.6 lb, compared with 22.6 lb for the original 350mm disc. The 18mm pad is thicker than the 15.3mm factory pad, so it lasts longer and absorbs more heat between changes. Every component is designed to resist the heat of extended track sessions.

Caliper and disc construction

On the C8 Corvette Z51, the CP9661 caliper mounts radially on a dedicated bracket at 180mm centers with a 42mm offset, with an M10x1.0 inlet thread. Stainless steel caliper hardware gives a long service life even with frequent pad changes. There are no dust boots to burn up at track temperatures. The championship-winning 72-vane AP Racing J Hook discs are fully floating. The discs use anti-knockback, anti-rattle attachment hardware. The disc metallurgy is designed for the temperatures seen on track, for a long service life. Spiegler stainless steel brake lines with a clear sheath reduce compliance compared with the OEM rubber lines. The caliper uses a commonly available 18mm thick pad shape.

Features

• AP Racing CP9661 six-piston calipers
• 355 x 32mm, 72-vane J Hook discs on floating hats
• About 12 lb less unsprung weight
• 18mm thick brake pads
• Pistons sized for the OEM master cylinder and ABS

What's Included

• One pair AP Racing CP9661 Radi-CAL Pro5000R racing six piston calipers
• One pair 355x32mm AP Racing CP7177, 72 vane, J Hook racing discs, with fully floating 6061 hard anodized aluminum hats and attachment hardware
• One pair caliper mounting brackets and hardware
• One pair Spiegler Stainless Steel Brake Lines with abrasion resistant coating
• Detailed installation instructions

Brake pads are not included.

Specifications

Video

Fitment notes

This rear kit fits the vehicles in the table below, which we confirmed against two sources using US model years. Essex has confirmed clearance with OEM Trident 20 inch wheel, Forgeline GS1R 18x12 inch ET57, Forgeline GA1R 18x12 inch, 19x12 inch, 20x11.5 inch, Forgeline VX1R 18x12 inch, 19x12 inch, 20x11.5 inch and Forgeline GT1-5 18x12 inch, 19x12 inch, 20x11.5 inch. Check your wheel with the Essex wheel fitment template before ordering.

Fitment