AP Racing Radi-CAL Front Kit 372mm - Subaru WRX, STI

The AP Racing by Essex Radi-CAL Competition Brake Kit is a front brake upgrade for the 2015-2021 Subaru WRX and WRX STI. It pairs AP Racing CP9668 Radi-CAL Pro5000R six-piston calipers with 372 x 34mm, 72-vane AP Racing J Hook discs on fully floating aluminum hats, built for track days and competition driving.

Why upgrade

Saves several unsprung lbs. from nose versus OEM brakes. Each caliper weighs 6.9 lb without pads, against 8.2 lb for the factory caliper. Each two-piece disc weighs 19.1 lb, compared with 21.8 lb for the original 326mm disc. The caliper takes a 25mm thick pad for long life and heat tolerance. Every component is designed to resist the heat of extended track sessions. Pistons are sized to work seamlessly with the OEM master cylinder and ABS. It works with the OEM rear brakes or a matching AP Racing rear kit.

Caliper and disc construction

On the Subaru WRX, STI, the CP9668 caliper mounts radially on a dedicated bracket at 180mm centers with a 42mm offset, with an M10x1.0 inlet thread. The caliper uses a commonly available 25mm thick pad shape. Ventilated, domed-back stainless steel pistons keep heat out of the brake fluid for a very firm pedal. Anti-knockback springs behind the caliper pistons limit pad knockback. The anodized caliper finish resists wear and deterioration at high temperatures. 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. Pads change with two bolts or a quick-change spring clip, with no caliper removal.

Features

• AP Racing CP9668 six-piston calipers
• 372 x 34mm, 72-vane J Hook discs on floating hats
• 25mm thick brake pads
• Pistons sized for the OEM master cylinder and ABS
• No caliper removal for pad changes

What's Included

• One pair AP Racing CP9668 Radi-CAL Pro5000R six piston calipers
• One pair 372x34mm 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 front kit fits the vehicles in the table below, which we confirmed against two sources using US model years. Call us about the Subaru Impreza WRX and Subaru Impreza WRX STI before ordering; we have not confirmed fitment for them yet. Check your wheel with the Essex wheel fitment template before ordering.

Fitment