AP Racing Competition and Radi-cal Brake Kits by Essesparts & URGE designs
 

URGE designs has parted with Essexparts to create 2 AP Racing Brake Kits using their competition parts catalogue

We felt the market was simply chasing large rotor brake kits as most designs focus bigger heat sinks
The problem with bigger heat sinks is it take more power to accelerate them, more force to stop them and they dont turn as quickly
URGE designs focused on increasing airflow and heat transfer to reduce brake temperature, rotor/pad wear and improve brake safety

The parts from our kits are used in professional racing and designed to stop ~2800 lb cars with 500-600 HP
So why go with oversized, heavier rotors reducing performance, when you can have professional racing parts designed for S2000 weight vehicles with twice the power

Essexparts AP Racing Competition Kit spec'd by URGE designs, $2800

• AP Racing CP8350 calipers and CP3862 rotors come from AP Racing catalogue and used on ARCA/SCA and rally car racing series
• CP3862 rotors have 60 vanes (OEM rotors have 24 vanes) dramatically flowing more air and have more surface area for heat transfer
• CP8350 4 piston calipers significantly stiffer than the single piston sliding OEM
• Calipers use steel pistons which have 15X lower heat transfer than OEM pistons, reducing heat transfer into the brake fluid
• ~14 lbs system reduction; 2 piece rotors, weigh ~1.5 lbs less than OEM each, Calipers weigh ~5.5 lbs less than OEM
• Lowest BBK maintenance cost; Low cost 2 piece replacement rings, longest lasting 20mm thick pads
• Spiegler Stainless brake lines improving brake modulation and feel
• Read full story on our website including wheel fitment and template

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Essexparts AP Racing Radi-Cal Kit spec'd by URGE designs, $4600

• Radical Pro 5000R series, CP9441 4 piston caliper up to 30% stiffer than non Radical-Cal calipers improving brake modulation and feel
• Stainless Steel caliper pistons reducing heat transfer between rotors and brake fluid as steel has 15X less thermally conductive than aluminum
• Scalloped pistons vent gases between the pistons and pads
• 4.85 lbs caliper >50% lighter than OEM caliper and 20-30% lighter than aftermarket 6 piston calipers
• AP Radical CP7472 rotors with 72 vanes (OEM has 24 vanes) significantly increasing air flow and surface area for heat transfer
• 338 x 26mm rotors weigh about the same of OEM despite triple the vane count
• Spiegler Stainless brake lines improving brake modulation and feel
• With in 1% of OEM brake bias, limiting ABS intervention. Most other aftermarket kits have 5-10% change in brake bias reducing brake balance and overall braking capability
• Please read our Radi-Cal story here

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email urgedesigns(at)gmail.com for quotes or post questions below

How do these match up size wise with the stop tech 328 for wheel fitment? I have a set of Volk CE28n on order size 17x9.5x50.

Clearance Template..

Just curious, why wasn't a rotor like the CP3908 used? 26mm seems to be on the skinnier side... is it just for the lighter weight (but at the cost of decreased thermal capacity)? What kind of guarantee can you give to show that these have sufficient thermal capacity?

Also, why the CP9441 over the CP9440? Seems like a smaller piston area on the 41 over the 40? Not to mention the piston sizes seem to be mismatched to our application on the 41

Great question.

Its all about right sizing the rotor for the application based upon vehicle weight and typical power levels.
First we look at our experience with our current non radical kit (still has the lowest replacement costs for pad and discs) that uses a 299x32 rotor and weighs 10.7 lbs. When we first worked with Essex to select a rotor out of the vast AP Racing catalogue, we searched for racing applications that had similar weight and power goals as the S2000. Those rotors were typically used on lower level stock cars that weigh 2800 lbs and make 500 hp around short track ovals. One of the harshest braking environments in the racing world.
Same S2000 weight, stops 500 HP cars and figured that was a great match for the S2000. After 77 kits sold with no fading issues, I feel our design choice was spot on. FYI, we have had these rotors on 24 hour endurance S2000 with no issues.

So lets think about the CP3908, bigger rotor, holds more heat, great. Do you need it? We have proven you dont. So why put more weight and cost into your car? That is 10 more lbs of total rotational weight or 40 lb static weight equivalent.
Would you swap your Aluminum wheels out for Steel? The Steel wheels are stronger, more resistant to dents, less deflection? You wouldn't, aluminum wheels provide the strength and durability needed to support your car and they weigh a lot less.
Also, If bigger rotors was better, then why the CP3908, why not the CP6572, its 380x34mm and weighs 22 lbs. At some point you cover the braking needs of the car and anything bigger starts to become a weight penalty. The CP3908 is more of a weight penalty than braking need in our opinion.

So its about right sizing and not oversizing.
The new rotors are thinner, but have more radial depth and thus similar weight to our current proven rotors, plus they have 20% more vanes to improved airflow and cooling. The same amount of vanes as the CP3908 as a mater of fact, with 4 lbs less weight.

As far as the Caliper, we want to match he brake force of the OEM system to not over trigger ABS. Brake force is radius times brake pressure. Since we have a larger rotor, we dont need to have as much caliper surface area.
By our math, this new system is closer to the stock total brake force than our current kit, which means less ABS engagement and more modulation.

I hope this answers your questions.

the template says its for the CP9441
but on your website it lists CP9448 as the caliper used

same template?

Same template.
Calipers are the exact same size. Just different piston sizes.
Great catch and questions.

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can you share what wheels and size/offset? Have the kit and have been able to find a suitable wheel to fit, leaving to advan rsii 17x10 right now

They're ce28s in the evasive spec. 17x9.5x50. There's a decent amount of room between the caliper and wheel. I compared the stoptech template and this one and this one has more clearance than the stoptech. Any wheels known to fit with the stoptechs should work with this set.