How to Identify AP Racing Brake Components

By Jeff Ritter

As the long-time exclusive North American importer and distributor for AP Racing brakes, Essex Parts Services has become an essential resource for information on AP products. We constantly receive emails, instant messages, and phone calls from customers around the world asking for spare parts and information about the AP Racing components they have in their possession. That conversation frequently begins with, “I bought some AP calipers on Alibaba. They’re red. I think they were on a Skoda at one point. I’m installing them on my WRX. I need piston seals, pads, and discs. Here’s a pic I took on my cell phone (the pic is blurry, upside down, and contains no part numbers). Oh…and I need everything for a track event this weekend!” :p

Calipers

They all look the same!

Calipers are one of the AP Racing’s most complicated products. AP has designed and manufactured an extraordinarily diverse range of both street and racing calipers over the years. Just because two calipers look the same at first glance, there’s a good chance they could have quite a few differences between them.

AP typically breaks their calipers down into ‘families’ or ‘ranges’ of related calipers. For example, AP’s Pro5000+ range of calipers were a staple in racing for a couple decades. The Pro5000+ range included several six, four, and two piston variants. Although there were only a few core caliper castings (the basic caliper body), AP used the same castings to produce a variety of calipers that had different widths, pad thicknesses, pad radial depths, piston sizes, some were leading (front side of the disc), some were trailing (back side of the disc), etc. When you combine all those variables, there is a lengthy list of potential part numbers to contend with.

If you wanted spare piston seals and pads for a caliper in your possession, you’d need to know the piston bore sizes, pad thickness, and pad radial depth to ensure you received the correct parts. That’s where the caliper part numbers come into play, and they are irreplaceable for communicating specific product data. Only the complete caliper part number contains all the relevant information for proper identification.

So what am I working with?

AP typically uses two caliper locations for complete part numbers. The first is on the underside of the caliper body: Flip the caliper over, and on the bottom of the piston bores will be an etching of the caliper’s complete part number, followed by that specific caliper’s serial number. The arrow near the part number denotes the direction the disc should be spinning when the caliper is installed, which can help ensure you’re installing the caliper on the correct side of the car.

Let’s look at an example to ensure clarity. The complete part number for the caliper in the image below is CP5060-23S4L. Below the caliper part number is this specific caliper’s serial number. If you look near the pistons in the top of the pic, there’s another number starting with CP5060. That is the casting or forging number for the caliper body, but it is NOT this specific caliper’s complete part number. Please note that the caliper body’s broader casting or forging number could be in other locations on the caliper body, such as near the inlet port.

Here’s another example, this time on a caliper from AP’s latest World Radi-CAL II road caliper range.

On AP’s latest Pro5000R Radi-CAL calipers, the caliper’s specific part number and serial number is now located on the inner half of the caliper near the inlet port (where the caliper connects to the brake line).

Again, the important takeaway is that only the number above the caliper serial number is the complete part number, and it will follow the CPXXXX-XXXXX alphanumeric format

Okay, but what does the part number mean?

If you’re the particularly curious type, an explanation of the AP Racing caliper part number system can be found in the image below. Applying the numbering system to the Pro5000R caliper in the image above (CP9660-3S4L), we can decode the caliper as:

1. From the CP9660 caliper family
2. Left hand caliper
3. Side feed inlet port
4. 4 lbs. anti-knockback springs behind the pistons
5. Stainless steel pistons

Iron Disc Rings

As with calipers, AP Racing has manufactured a tremendous array of brake discs over the years in varying sizes, shapes, slot patterns, etc. While some can be found in their current print catalog or on their website, many of the part numbers are no longer sold, and there are no longer references to them anywhere. To compound the problem, some companies have offered their own line of discs manufactured by someone other than AP Racing, but then applied AP's numbering convention to them! As a result, figuring out what exactly that hunk of iron in your hand actually is, may be more challenging than one would expect.

To identify a genuine AP Racing iron disc, you need to examine the outer radius of the disc. The part number will be stamped into the disc wall somewhere around its circumference. Please see the pic below as a reference. If it doesn’t have a CP part number stamped on the outer edge of the disc wall, it most likely isn’t a disc manufactured by AP Racing.

AP Racing Disc part numbers use the same basic naming convention as calipers: CPXXXX-XXXX. The graphic below explains how to decipher disc part numbers.

Caliper Brackets and Disc Hats (aka Bells)

While AP Racing has produced thousands of calipers and discs over the years, they’ve produced relatively few ‘complete brake kits’. The typical enthusiast views a ‘brake kit’ as including everything required to adapt and apply calipers and discs to their specific car (custom caliper adapter brackets, custom disc hats, and brake lines). AP has focused more on the manufacture of individual components, and relied on their distributors such as Essex to apply those components to specific vehicle chassis in their respective market. Therefore, if you’re looking for replacement components to apply AP Racing calipers and discs to a certain vehicle, you’ll likely be dealing with components manufactured by some entity other than AP Racing.

In complete brake kits produced and sold by Essex Parts Services, we include components that we design and manufacture in the USA. Below are examples of our billet aluminum caliper brackets and disc hats. Our Essex part numbers use a slightly longer alphanumeric system that denotes a product category, product type, and specific chassis code. Please see the pics below for examples. If the bracket or bell you have has a part number that differs dramatically from what you see below, it wasn’t manufactured by Essex. As such, it’s going to be either incredibly difficult or impossible for us to provide a replacement. Doing so would be akin to calling Dell Computers and asking them to sell you a part for your MacBook. We would have no idea how the part was made, the materials used, the dimensions involved, etc. In such cases our suggestion will be for you to either track down the original manufacturer of the chassis adaptation components in your brake kit, or you'll have to find a machine shop to fabricate one for you. The only other option would be retiring your current adaptation components and installing those of Essex design (if we offer them for your chassis).

Summary

Hopefully this article has armed you with enough knowledge to quickly identify the components related to your AP Racing brakes. If you could please take a few minutes to collect and prepare the information above prior to contacting Essex, we'll be able to give you the prompt service you deserve!