AP Racing Radi-CAL Competition Rear Kit 340mm - Porsche 987, 981, 718

This AP Racing by Essex Radi-CAL Competition Brake Kit upgrades the rear brakes on Porsche's mid-engine Boxster and Cayman. It covers the 987 Boxster S and Cayman S, every 981 except the GT4, and 718 base, S, T and 2.5-liter GTS models, using AP Racing CP9451 Radi-CAL four-piston calipers and 340 x 28mm, 48-vane heavy duty J Hook discs. Unlike many rear big brake kits, it keeps the factory parking brake working.

Why upgrade

Mid-engine cars carry more weight over the rear axle than most, so the rear brakes do a bigger share of the work on track. The factory 299 x 24mm disc is replaced by a 340 x 28mm floating disc that adds diameter and thickness yet weighs 11.1 pounds against 13.95, and each caliper is lighter than stock at 4.85 pounds. Pistons are sized to work with the OEM master cylinder and ABS, so brake balance stays predictable, and the kit pairs naturally with a matching AP Racing front kit.

Caliper and disc construction

The CP9451 is a hard anodized Radi-CAL caliper with an asymmetric, computer-optimized body. Stainless steel pistons, anti-knockback springs and high-temperature, low-drag seals keep the pedal consistent session after session. The CP6565 heavy duty discs use 48 vanes and fully floating 6061 hard anodized aluminum hats so the iron ring can expand freely with heat.

Features

• AP Racing CP9451 Radi-CAL Pro5000R four-piston rear calipers
• 340 x 28mm, 48-vane heavy duty J Hook discs on floating hats
• Retains the OEM parking brake
• Lighter than the factory rear brakes despite the larger disc
• Pairs with AP Racing front kits for the same cars

What's Included

• One pair AP Racing CP9451 Radi-CAL Pro5000R racing calipers
• One pair 340x28mm AP Racing CP6565 heavy duty 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

Fits the 987, 981 and 718 models below; not for the GT4, 718 Spyder or 4.0-liter GTS. Clears the OEM 19 inch wheel from the 2010 Cayman S, APEX SM-10 18 x 10 ET36, OZ Alleggerita HLT 18 x 10 +40 and Volk Racing TE37 Ultra 19 x 10 ET40 without a spacer. Call us about 987 base models, the Cayman R and the Boxster Spyder.

Fitment