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Subaru STI on Lift with parts in front of car.

The Best Brake Upgrades for your 2018-2021 Subaru STI!

Written by: The Modfather

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Time to read 6 min

Our recent inaugural enthusiast profile featuring Ron's beautiful, World Rally Blue, 2021 Subaru WRX STi should prompt inspiration within our community. The article outlines a long list of STI Brake Upgrade that contributed to the vehicle’s upgrade. This aligned with his desire for optimum street performance and his dream to participate in light track and autocross events like those he briefly experienced at the 2023 Staggered. A strong and reliable engine is great, but responsive brakes are critical. If his car doesn’t stop, this beautiful Subaru will become a pile of metal in a salvage yard. This article will focus on the details of his upgraded braking system.

The Challenge: When Should I Do My Brakes?

There are many situations in the world of Subaru Performance that would call for a brake system upgrade, repair, or replacement. This phase of the modification should make sense to those who want to move from one level of performance to another, but it is important for every owner and enthusiast to first grasp the importance of an upgrade when specific signs appear. It is important to state that a vehicle experiencing brake problems will exhibit unusual noises, vibrations felt through the brake pedal or also through the steering wheel. Depending on the brake pad you may also hear an audible persistant squeak coming from the brake system when the pedal is depressed, this is the wear indicator on the pad telling you it is time!

Whether you are pursuing performance or daily driving, when your vehicle’s braking doesn’t feel stable it is very important to investigate the issue. Ignoring the warning signs may cause rotors to prematurely wear or the brake system as a whole to become less reliable. Since a driver of a sports model like the STi does not always observe the practices of the average daily driver, many manufacturers recommend that both front and rear brakes should be reviewed at least once every 15,000 miles or 12 months and replaced as need. In his modification, Ron’s choice of components did not only satisfy his plans for future track performance, but also ensures his safety in all conditions.

Step 1: Removing Your Stock Brake Pads

The STI Brake Calipers by Brembo make pad swaps super easy! You will find one pin in the center of the caliper secured by a nut on the rear of the caliper, remove that nut and you will be able to remove the center pin. The remaining two pins can be removed by utilizing a small punch to press the pins out towards the strut.  Once those pins have been removed you can pull the pads out from the top of the caliper itself. 

Step 2: Removing Your Brake Caliper

The next step in the process once the brake pads have been removed is to remove the brake caliper! You will need to remove this piece to be able to access and remove the stock rotor in the next step. Start by removing the two bolts which hold the caliper to the hub and then finally if you are doing brake lines you can disconnect that line now and ensure you have something ready to drain the fluid from the line into. 

Step 3: Remove Your Stock Rotors

With the caliper removed or tucked away you need to get your factory rotors removed. Depending on how long the factory rotors have been installed on the vehicle, you may notice the rotors themselves may feel stuck to the hub. You can take a mallet to the corners of the rotor itself or use a punch from the rear side of the disc to help separate the rotor from the hub itself. Pro tip, most brake rotors have a threaded hole that you can utilize to pass a bolt through and lift the rotor from the hub. 

Step 4: Installing Your New Rotors

First you'll want to make sure that the hub is clean and clear of any debris to ensure the best mating surface possible for the new rotor. Any debris left behind could cause the rotor to sit unevenly on the hub leading to brake pulsation. Once you have the hub clean you can proceed with installing the rotor on the hub. Be sure to use a brake parts cleaner to remove any oil present on the rotor disc. 

DBA was the brand chosen to upgrade to high performance rotors. The DBA 4000 Series XD Drilled Rotors are designed with a surface finish that provides added cooling benefits - called Thermal Stability Profiling - above the HD specifications. This drilled and slotted rotor design allows all gasses trapped between the pad and the rotor to escape during use ensuring consistent, positive contact. The design is innovative but also aesthetically agreeable to the STi style. Again, another component that is perfect for a driver like Ron who wants performance and stability both on and off the track. 

Step 5: Re Install Caliper and New Brake Pads

Ceramic Front and Rear brake pads from Hawk Performance. As we all know, the primary complaint of many drivers is the issue of excessive dust. These pads are manufactured with a unique ceramic composite material to maintain ultra-low dust and low noise while sustaining high friction levels and improved stopping power. Hawk Performance was chosen because of its tested performance as a premium disc brake pad that will ensure the complete brake system will work more effectively on the road or track. The Hawk pads come with the Gearhead Grease Pak which includes specially designed high temperature brake part lubricant ready for application during the assembly process

To install your new Brake Pads into the factory caliper be sure that the pistons inside the caliper itself are compressed to allow the pad to slide freely into the body. If the pistons are extended we recommend using a caliper piston compressor to safely push the pistons back into the body. Many manufacturers will include grease to apply to the rear of the pad which meets the pistons, this grease can be used on slide pins as well if need be! Once the pads are loaded into the caliper you can place the retaining clip which secures the pad and install the the pins in the order they were removed. 

Step 6: Install New Brake Lines and Bleed The System

The Front and Rear brake lines were provided by Rotora, one of the premiere manufacturers of brake components. Rotora’s Stainless Steel Braided Brake Lines are incredibly stable and secure under extreme threshold braking. Ron’s research found that the stainless steel lines provide precision brake performance in all conditions, prevent brake hose expansion under pressure, and most importantly, provide a stiffer pedal feel by maintaining consistent brake pressure. 
 

Installing new brake lines is a easy yet tedious process. It is best to purchase a set of brake line wrenches to ensure proper contact with bleeders and fittings. Normal wrenches only contact two sides, and can cause the fittings to strip. It is best to remove a line, and then reinstall the new line to prevent fluid loss. Be sure to verify that the mounting tab on the line is secured to the hub and both the chassis and caliper side fittings are secure before proceeding onto another corner of the vehicle. Good brake lines are nothing without a performance brake fluid, Motul RBF600 is a great choice for street cars that will see some high performance driving on track!

Step 7: Don't Forget Your Accessories!

While finalizing the details of his modification, Ron realized that most issues typically arise when brakes are put to the test under extreme conditions, such as on a race track. Excessive heat can lead to brake fade after only a few laps, but often its not the brake pads that are to blame. Brake fluids have a "non-compressible" characteristic enabling them to effectively transmit motion from the brake pedal to the brake pads and discs of the vehicle. 

The Radium Master Cylinder Brace for the 15+ WRX/STI is an additional way to improve brake feel in the VA Chassis. This Master Cylinder brace helps prevent firewall flex from heavy braking. This brace useless factory mounting holes on your drivers side strut tower and applies pressure to your master cylinder, opposing your brake petal force. The Boomba Racing Brake Cooling Deflector Kit for the Subaru WRX/STI helps to channel air towards your caliper and rotor when driving. The cooling deflector mounts securely to the A-arm using a hole that is already pre-made for a completely reversible installation. Ground clearance is not compromised and there is no need to remove your fog lights or drill any holes. This kit can be installed easily in your driveway using a jack and jackstands.

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