Wilwood Red AERO4 Rear Disc Kit, Drilled 14-Inch Rotors and Factory Parking-Brake Interface, for Selected BMW 328i/323i/325i

The red-caliper version of this BMW rear kit uses drilled-and-slotted 14-inch Spec-37 rotor rings on the matched parking-brake hats. It changes the hydraulic service brakes while retaining the specified original mechanical parking system and factory hub arrangement. For this conversion, component matching remains essential. Its manufacturer is Wilwood Engineering, founded by Bill Wood in 1977 and based in Camarillo, California. Wilwood designs and manufactures disc brake systems for motorsport, street-performance and specialized applications; its component range includes calipers, brake rotors, master cylinders, valves, fittings and brake lines selected to work within a complete system.

Technical Details

• Rotor: 14.00 in; 355.6 mm outside diameter; 1.10 in; 27.94 mm thickness. Material: Spec-37 Iron. Construction: Vented. Friction-face style: SRP Drilled & Slotted.
• Rotor-hat material: Iron. Hat offset: 1.700 inches; this hat dimension is separate from axle offset.
• Rotor surface finish: Black Electro Coat.

• Calipers: 4 stainless pistons per caliper; radial mounting; forged aluminium bodies. Color: Red. Finish: Red Powder Coat. Inlet thread: 1/8-27 NPT.
• Caliper family: AERO4. Brake-pad compound: BP-10.

• Manufacturer: Wilwood; manufacturer part number: 140-13583-DR. Supplied quantity: Sold as a kit.
• Application category: Rear Brake Kits - Street Performance. Axle/spindle category: Rear Kits. Brake function: Disc; Parking.
• Separate wheel hubs included: No. Retain only the hub arrangement specified for this kit.
• Mounting hardware included: Yes. Spindles included: No. Master cylinder included: No. Brake booster included: No.
• Flexible brake lines included: Yes; matched line kit 220-13647, 8.00 inches nominal length.
• The rotor hats retain the specified original mechanical parking-brake shoes and assembly; a replacement parking-brake mechanism is not supplied.

• Wheel interface: 5 x 4.72 in; 5 x 119.89 mm. Rotor/hat wheel-stud clearance: 0.490 in; 12.45 mm.
• Nominal minimum wheel diameter: 18 in; 457.2 mm. Verify the full wheel-clearance drawing; diameter alone does not establish barrel or spoke clearance.
• Housing/spindle flange: OEM. Flange/axle offset: 0.00 in; 0 mm.

Fitment & Compatibility

Confirm the rear application independently of any front big-brake selection. The table lists specific 323i, 325i and 328i versions and does not establish rear compatibility for 335i or the 1 Series. Check parking-shoe fit, ABS configuration and the DS1039 wheel outline.

Manufacturer Documents

• Wilwood product specifications and wheel-clearance drawing
• Installation instructions

PMB Performance can help work through the mounting and wheel-clearance details before purchase. Our parts and fitment support is backed by over 20 years of experience; include measurements of any modified axle or spindle.