Essex Designed AP Racing Big Brake Kit Installed on our 2015 WRX!


We've been busy little bees since taking delivery of our 2015 WRX last Friday! As those who already own one of these cars know, brakes are not one of its particularly strong points. We've gotten feedback from several of the shops we work with, telling us that the brakes are inadequate for track use. We're on it!

Since the '15 WRX shares the same spindle as the last generation STI, our Essex Designed AP Racing Competition Big Brake Kit for the 2004-2014 WRX STI bolts right onto the new WRX without any modifications! Our engineering department evaluated the 2015 components, and the same calipers and discs found in our last gen. STI kit work perfectly for the new WRX, maintaining appropriate brake bias and providing plenty of thermal mass.

That said, our STI kit will NOT clear the 2015 WRX OEM 17" wheels. You would need a roughly 6mm thick spacer to clear the OEM 2015 WRX 17's when running our STI kit. If you're running aftermarket wheels, you can check the wheel clearance for our STI kit here.

For the final production version of our 2015 WRX big brake kit, we're going modify the design of our caliper brackets and disc hats to push the components further inboard, and we should be able to fit them under the OEM 17's. The calipers and brake lines will remain identical to those in our current STI kit however. We expect our final production 2015 brake kit to go on sale in early August. However, if you have an upcoming track event and you're in a pinch for a solution now, our STI kit is a great option. The only thing you'll be losing is a small amount of wheel clearance, and if you're only running aftermarket wheels, that may not even matter to you.

Shave 24.4 lbs. of Unsprung Weight!

Now to the good stuff...our Essex Designed AP Racing Competition Big Brake Kit saves 24.4 lbs. from the nose of the 2015 WRX, or 12.2 lbs. of unsprung weight per front corner!

Weight in lbs.


Per side

Front Axle

Front OEM Caliper/bracket



AP Racing CP8350/bracket



Front Caliper Weight Savings



Front OEM disc (315x30mm)



Front AP Racing CP3908 (325x32mm)



Front Disc Weight Savings



Total Big Brake Kit Weight Savings



OEM 2015 WRX Brakes on scale (this one includes pads, hence the slight difference from the numbers above).

38.8 - 27 = 11.8 *2 (both sides of car) = 23.6 lbs. unsprung weight removal!

What else can it do?

Not only does our kit save a ridiculous amount of unsprung weight, it will give the following benefits over the OEM front brake system...

Caliper Benefits:

  • Incredible array of inexpensive race pad options at prices that are consistently 15-20% less expensive than the 2015 WRX front pad shape. The pads in our calipers are 20mm thick, vs. the 17mm thick OEM pads, and large enough to handle typical lapping/race session
  • Simple pad change with one bolt, and no need to remove caliper (unlike the OEM slider caliper which requires removal to change pads).
  • Very easy to see how much pad life is remaining without wheel removal
  • Stainless steel caliper pistons that keep heat out of your brake fluid to resist fluid fade during extended track sessions
  • Pistons sizes carefully selected to maintain correct factory brake bias
  • High temperature, low drag piston seals that will hold up to track temps better than OEM components= less rebuilding and longer service life
  • No dust boots to burn up and make a big mess
  • Mitigation of pad knockback due to 4lb. anti-knockback springs in the calipers
  • Less chance of damaging bleed screws or crossover tubes when changing wheels due to built-in protection
  • Anodized caliper finish that is resistant to wear and deterioration during heavy track use
  • Stainless steel caliper hardware for a long caliper service life under frequent pad change conditions
  • Extremely compact package for superior wheel fitment
  • Lifetime professional caliper rebuilding support by Essex (at a fee)- pull off your calipers, send them to us, we clean, inspect, and rebuild them

Disc Benefits:

  • High airflow, heavy duty, 70 vane AP Racing J Hook brake discs that are over 4 lbs. lighter than the OEM units, despite being considerably larger than stock (325x32mm vs. 315x30mm).
  • AP Racing J Hook slot design that gives more pad bite/feel, and distributes heat evenly throughout the disc
  • Disc metallurgy specifically designed to handle the temps typically seen on track offers a long service life
  • Spare discs available at an extremely competitive replacement price ($250 per iron disc).

Other Benefits:

  • Highest quality Spiegler stainless steel brake line with clear sheath that reduces compliance over OEM rubber design.
  • You will look way cooler than you did with the lame-ass OEM brake setup, so girls will fawn all over you!

What about the Rear Brakes?

Since our kits are designed to mimic the OEM brake torque output of the factory setup, it is completely fine to run our front-only brake kit. Due to the drivetrain layout and weight distribution of these cars, they actually use very little rear brake compared to other platforms. Therefore the greatest performance bang-for-the-buck will definitely be found in front brake upgrades. That said, we are planning to do a complete rear BBK as well, and we are currently pulling the rear brakes apart and considering our options.


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