Complete rear AP Racing by Essex Road Brake Kit for the BMW E90/E92/E93 M3 & 1M Coupe:

• Retains full function of OEM parking brake
• Removes 10 lbs. unsprung weight vs. OEM, despite being far larger
• Painted calipers with dust boots add durability in inclement weather conditions
• Low noise, vibration, and harshness for a very OE-like experience during daily driving
• Features the game-changing AP Racing Radi-CAL caliper technology with a red, black, or silver painted finish
• Huge 380mm AP Racing J Hook, fully-floating 2-piece discs
• Pistons sized properly to maintain proper brake bias and work with the OEM master cylinder and ABS system
• Designed to mate with our front AP Racing Road Brake Kit

WHAT’S IN THE BOX?

• One pair AP Racing CP9541 World Radi-CAL II four piston calipers
• One pair 380x28mm AP Racing CP5914, 72 vane, J Hook 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
• One set of Ferodo DS2500 Brake Pads
• Detailed installation instructions

CALIPERS

RADI-CAL

“Radi-CAL” is a blanket term used to describe AP Racing’s patented asymmetrical brake caliper design. Radi-Cal technology is grounded in Computer Aided Design (CAD) and Finite Element Analysis (FEA), and allows for organic, alien-looking designs that are a radical departure from conventional caliper designs of the past. Radi-CAL’s are widely considered the pinnacle of current brake caliper technology. Since their inception in 2007, these revolutionary calipers have amassed a lengthy string of race victories at all levels of professional motorsport, while redefining brake performance expectations. For more details on the design concept and what these calipers have achieved in professional racing, please visit our blog and read The AP Racing Radi-CAL Story.

The key benefits of the Radi-CAL design:

• Massive Stiffness Increase– A 30+ % increase in both static and dynamic stiffness vs. conventional calipers allows for far less deflection under load, which means superior pedal feel & modulation, more even pad wear, and longer caliper service life.
• Considerable Mass Reduction– Removing all extraneous caliper mass lowers the caliper weight, despite the huge stiffness increases.
• Optimized Airflow– Air moves around and through the caliper more efficiently, providing superior heat evacuation and cooling.
• Efficient Packaging– The asymmetric caliper profile allows the caliper to fit into tighter spaces.

CP954X WORLD RADI-CAL II (WRII)

It took eight years, numerous generations of the design concept, and advancements in manufacturing techniques, but the Radi-CAL finally evolved into a viable solution for enthusiasts of all levels and budgets. While many products are supposedly born in racing, there can be no doubt about the Radi-CAL pedigree. These calipers are direct descendants of the current crop of F1 and NASCAR Cup calipers. They don’t look ordinary, because they’re not ordinary. They’re the epitome of racing design: elegant, sparse, and brutally effective. And while they embody and employ the Radi-CAL design philosophy of the past, they also add some outstanding new features that enhance their practicality, convenience, and appeal. Quite simply, they are the most technologically advanced brake calipers that have ever been within the common enthusiast’s grasp.

Radi-CAL = Massive Dynamic Stiffness Increase

Over the years, many different strategies have been employed to shrink the brake caliper footprint while maintaining adequate stiffness: More robust caliper bridge designs, two-piece calipers with steel through-bolts, exotic materials (i.e. Beryllium, MMC), forging rather than casting, monobloc design, etc. All of these innovations pushed calipers towards becoming lighter, smaller, and stiffer. However, until the advent of the Radi-CAL, the same basic rectangular, boxy shape remained the accepted standard.

Is a rectangular box really the most appropriate and efficient shape for a brake caliper? AP Racing has now proven that it is not. As a brake caliper clamps brake pads against a spinning disc, a tremendous tangential friction force occurs between the pads and the spinning disc. In other words, the caliper is pulled strongly in the direction of the spinning disc, as represented by the downward pointing arrow on the right side in Figure 1 below. The caliper resists that force via the spindle hard mounting points, depicted by the upward arrow on the left. The dynamic load placed on the caliper twists or pulls the caliper into a parallelogram shape.

DISCS- AP RACING J HOOK 

AP Racing J Hook discs have achieved near-legendary status in both professional and amateur racing for their durability and crack resistance. They have been proven time and again, winning many races and championships (ALMS, Rolex, Grand Am, etc. While the discs we’re employing in our Road Kits have an impeccable racing pedigree, we’ve also added some features that will keep them composed and well-mannered on the street).

Two-piece Floating Design with Aluminum Hat 

As is the case with most metal, iron brake discs grow substantially when heated. As it is heated, a disc expands radially, increasing in diameter and circumference. One-piece disc designs run into problems when this occurs. Look at the picture below and imagine the disc is being heated on the track. As the disc expands, the outer edges of the disc are pulling away from the center of the disc, but there are no built-in provisions to allow for that expansion. The edges of the disc therefore pull, lift, and distort, which is called coning. Now imagine that disc vertical on the car, running in your caliper. Coning directly impacts the brake pads’ contact with the disc, leading to uneven wear and tapering, and even a long brake pedal. Two-piece discs on the other hand, compensate for the expansion of the disc as it heats. This is accomplished by building ‘float’ into either the disc itself, or the disc hat/bell. In this case, the float is in the hat. As the disc heats and expands, the hat bobbins slide in the channels and eliminate stress on the iron disc ring, leading to less distortion and fewer cracks.