Quote:
Originally Posted by 8k3
If this was covered please ignore. There are various AP setups for the E92, Radi-Cal being what seems to be the latest. How is this setup an improvement or at least compare?
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I didn't miss or forget about this question...just didn't have time to address it properly! So here it is...
Essex and AP Racing Relationship- How it works
I’ve had a number of customer questions regarding our relationship to AP Racing, to Stillen, and how our kits compare to other options on the market generally labeled “AP Racing.” Hopefully this post clears everything up!
Essex is AP's exclusive importer and distributor for competition parts in North America. Stillen is AP's exclusive importer and distributor road car parts in North America. Essex and Stillen are completely different entities. Stillen buys AP Racing brake fluid from Essex, and we refer customers to each other based on the customer’s needs. There are no other ties between the two companies.
Essex has been in the racing business for roughly 30 years. You can read about our history here. We service ALMS, IndyCar, NASCAR Sprint Cup...from the pinnacle of pro racing all the way to club racers and track day enthusiasts. We have twenty+ people on our staff (including our own engineering department).
Our chief engineer was the director of engineering at Tilton for 14 years prior to coming to essex. He has immense brake and clutch knowledge and design experience. We also have a full-time AP Racing engineer who works from our office (he's been with AP for 35 years). We have a brake dyno, disc burnishing cell, and we are AP's only authorized caliper reconditioning center in North America. You can
see more about our services here.
In England, AP Racing sells their own brake kits for various platforms, including the M3, which are listed in their catalog and on their website under "Factory Big Brake Kits." They create both road and competition systems under the “Factory Big Brake Kit” banner. Their Factory Competition Big Brake Kits would be most similar to what Essex sells in North America. AP puts fantastic complete kits together, but they aren’t always the ideal kit for our local North American market. Customer needs in various regions tend to differ, sometimes greatly. Both where and how the drivers in different regions use the brakes may be different. In many cases, the actual cars being used are quite different! As we all know, euro-spec cars aren’t always the same as USDM cars. Also, you don’t typically see many Caterhams at Road America, and there aren’t that many Corvettes tearing up Silverstone on most days!
As AP’s representative in the racing market, it is our job to assess customer needs and fulfill them with the appropriate AP Racing products. What we do is buy the calipers, iron discs, and attachment hardware from AP Racing. Our engineers work with our in-house AP engineer to design complete kits geared towards the North American market. We share data with AP depending on who has the car, when they have access to it, etc. For example, we bought a C7 Stingray long before AP ever had the chance to look at one in England. We then build the required parts to adapt the AP components to the USDM cars (caliper brackets and disc hats). Many of our kits, such as our e92 kit, have custom features such as the machined, ventilated, domed-back pistons. These specs are unique to the Essex components, and aren't available elsewhere in the world.
The AP Racing Radi-CAL
The racing Radi-CAL was introduced in 2007 and is considered by most to be the pinnacle of brake caliper design. They’ve now won countless races at all levels of motorsport. “Radi-CAL” is a blanket term used to describe AP Racing’s patented asymmetrical caliper design and process. The Radi-Cal technology is based on Computer Aided Design. The process allows for stiffness and weight optimization far beyond what was previously thought possible in a brake caliper. Compared to a more traditional design, caliper material is redistributed based on dynamic, rather than static, loads placed on the caliper. In other words, the caliper is not designed to be a stiff box to hold pads while sitting on a table. It’s designed to be an incredibly stiff box to press pads against a disc on a car doing 200mph and decelerating at 4 G’s. AP’s brilliant engineers figured out how to assess the dynamic real-world stresses placed on the calipers under race conditions. They then altered the fundamental structure of the caliper to accommodate those loads. The resulting designs were dubbed “Radi-CAL” because of their radical departure from conventional caliper design.
The result is a very alien looking design. The mass of the caliper is located on a diagonal, rather than a square box. Radi-CAL designs contain many voids/empty spaces. That is because any unnecessary mass is either removed from the caliper, or relocated to where it is actually needed to accept a dynamic load. Many racing Radi-CAL’s also incorporate a provision for an air bridge. A channel is cut into the top of the caliper that allows for air to travel from a brake duct, across the top of the caliper, and through the outside caliper pistons to the outer disc face. The air bridge itself is constructed of carbon fiber to keep the weight down. These intricate calipers are usually machined from proprietary aluminum alloy billets. As one can imagine, machining away all of that material to achieve the final form is both time-consuming and costly. As a result, the price of these calipers is prohibitive for the average club racer or time-trialer. AP has introduced, and continues to work on, some new forged Radi-Cal’s, which are less costly to produce, and do show some promise for use in amateur motorsports.
Below are some pics of the racing Radi-Cals that we sell to our professional racing customers. You can see all of the design elements that I mentioned above.
Originally designed for German Touring Car (DTM)
Aussie V8 Supercar
NASCAR Caliper
Formula 1 Caliper hanging out on my desk on a sheet of paper.
Can you buy these racing Radi-Cal’s for your car at this time? The answer is a qualified yes. As mentioned above, the racing Radi-Cal calipers are extremely expensive. In many cases one caliper costs as much or more than our complete standard front six piston kit. Again, that’s just one caliper…nothing else. The other issue is packaging. The asymmetric design makes the calipers wide, which makes wheel fitment difficult on many platforms.
Last year AP Racing decided to take the Radi-Cal concept and apply it to road calipers. The result is what AP calls their “World Radi-Cal”. In a similar fashion to what we do for our Essex Designed AP Racing Competition Big Brake Kits, Stillen puts together their own road car brake kits using these calipers. They’ve been doing so for many years, and in the past they’ve used conventional AP Racing road calipers.
The CP5060 racing caliper we use in our Competition Kit weighs 6.2 lbs , and the six piston World Radi-Cal weighs 10.25 lbs. Our rear CP5040 caliper weighs 5.8 lbs. vs. 7.4 for the World Radi-Cal four pistons. The calipers in our kit have ventilated, domed back, stainless steel pistons with anti-knockback springs and no dust boots. The calipers we use have been around a long time, and as such, have a huge range of available pad compounds from all of the major pad manufacturers. The World Radi-Cal’s have aluminum pistons with dust boots and no springs, and have a painted finish. The AP Racing discs we use in our front kit are a 355x32mm, 72 vane, heavy duty endurance design that has won championships in pro racing. With the hat installed they weigh 17.6 lbs. Stillen is using 370-380mm x36mm, 48 vane discs, which are a few lbs. heavier.
Overall our Essex Competition Kit shaves roughly 40 lbs. of unsprung weight from the car, whereas the World Radi-Cal road system is very close to the stock weight. They’re both outstanding designs, but they’re designed with different goals in mind. Whichever option is right for you will depend completely on how and where you will be driving your car.