It’s been a while since Project WRX has seen a racetrack, but there’s a good reason for that. At its last outing on the high-speed Big Willow Racetrack in Willow Springs, CA, I was scared out of my mind. Not because of the near-triple-digit corners or the fifth-gear straightaways — those were all exhilarating, actually. It was when it came time to slow the WRX down from those high speeds where I got a taste of the butt-puckering, oh-shit-I’m-going-to-fly-off-the-track! sensation.
After a mere two laps, it became inherently clear that the stock WRX braking system, even equipped with HAWK HP PLUS brake pads and Project Mu brake fluid, wasn’t up to the task of handling the rigors of the track, producing extreme brake fade and a pedal that saw the ground more than a couple times.
Having an inadequate brake system can not only kill the fun out of a track day, it can also kill you. At a track like Big Willow, going off track at speeds of 80–100 mph can end with dire consequences, and nobody ever wants to face that situation. That’s why I decided an upgraded brake system was a must before the WRX saw any track time again.
At first, I thought an OE-style big brake upgrade using STI Brembo 4-piston caliper fronts and 2-piston caliper rears with bigger rotors would be the hot ticket, but the more I researched, the more complex I found that route to be. The STI brake system doesn’t bolt up to the WRX, so you’ll need to replace hubs or look at alternative adapter plates that will hold the calipers in place, but there are still issues with the rear parking brake, matching the proper brake master cylinder and so on. Bottom line, I wanted a WRX-specific brake upgrade and this wasn’t going to cut it for me.
Digging around on the Internet, I found that Stillen.com had a complete AP Racing big brake solution for the WRX. This very kit reminded me of when we had a Nissan G35 project car that suffered from the same braking issues at the track, and after an AP Racing big brake upgrade, the problems were nonexistent and we recorded faster lap times.
AP Racing is synonymous with being a leader in the performance braking world, with more than 50 years of racing experience in F1, NASCAR, Grand Am and World Rally Championship. Its equipment is built to withstand some of the most grueling race conditions out there, and through its racing lineage the latest in materials, coatings and design have been developed, tested and trickled down to production units for street cars. While other manufacturers use aluminum mono-block calipers, AP Racing chooses to use a lightweight aluminum two-piece design with high-strength bolts because the company feels that the two-piece design has greater stiffness qualities that results in consistent, firm brake pedal feel. The hard-anodized and painted calipers also come with dust seals on all its pistons and anti-rattle clips to ensure durable, long-lasting and quiet operation while being maintenance free unlike most hardcore race kits that need to be serviced often.
The Subaru WRX kit comes with 6-piston front and 4-piston rear calipers with 14-inch front and 13-inch rear rotors. The two-piece rotors employ aluminum top hats to reduce weight, while the directional vanes aid in cooling the cast-iron discs that are slotted to provide an aggressive pad bite and have been proven to work effectively on the track.
The AP kit leaves nothing unattended, providing all the necessary hardware like stainless steel brake lines, AP Racing brake fluid, Stillen high performance brake pads, brackets and clips for a quick and easy bolt-on. More importantly, knowing that this system has been properly developed for the WRX brings great piece of mind. Once installed, there’s little worry of anything going wrong. Confidence in your brakes is a great thing to have both on and off the track, and it comes naturally and easily with a big brake kit like this.
So just how well does the AP Racing kit perform and feel on the WRX? The difference is night and day. With the stock system, the brake pedal was inconsistent in feel, and, despite several brake bleeding attempts, would feel tall one day and short the next. With the AP kit, the brake pedal instantly came up and settled into one spot.
There’s no sign of the instant jerky reaction that’s common when upgrading to bigger calipers; the pedal transitions smoothly from low to high braking force as more force is applied. That’s why on the street it’s hard to notice the 6-piston calipers up front and 4-pistons in the rear until you need to stop in a hurry. That’s what I love best about the setup — it performs like a firm, OEM brake system, but with much more clamping power.
Even with my seat-of-the-pants testing providing a very noticeable difference, I wanted to get some hard numbers to further prove the point that big brakes are worth their weight in gold, even when it’s a whole lot of it. The problem was, I had not gotten lap times when I ran at Big Willow, so that meant I needed a different testing environment.
Even though the track would show the biggest difference, I turned to a simple straight-line braking test to see if there would be any improvement in braking distances. I’ll admit that in theory this seemed like a great idea, but once the actual testing began, I realized the small variables in the driving, outside temperature and how much tires and ABS play a role in stopping the car were all variables that would be hard to control and repeat.
Despite the variances, I still ran the test and with the help of the Motor Trend staff, who let me sneak into their testing session, I was able to get some 100–0 mph braking distances. I wanted to test the high-speed braking because it would best represent the speed seen at a track.
Even with the OEM brakes having aggressive Hawk HP Plus pads and high-temp brake fluid — a worthy brake setup — the AP Racing kit managed to better the stock system by a solid 9 feet. It may not seem like much, but in real life that’s a significant amount. There’s more to the story, though; what the numbers don’t tell is how mushy the brake pedal felt after 10 runs with the stock brakes.
They were also smoking quite profusely, and the rotors were so scored and pitted that they were scrap. That’s only after 10 runs — I can’t imagine what they would have looked like after 10 more. The exact opposite occurred with the AP Racing kit: the pedal feel didn’t change, the rotors didn’t score and the system performed true to its nature.
Project WRX is finally ready for another track outing, but this time I’m not going to have to worry about the brakes being the shortcoming. Instead, I can attack the track with complete confidence.
AP Racing Big Brake Upgrade