2015-2021 Subaru WRX Front vs Rear Brakes: What Wears First and What to Replace

By Core Brake Parts Tech Team — Circleville, OH warehouse

On a 2015-2021 Subaru WRX, the front brakes almost always wear out first. The fronts carry most of the stopping load because weight shifts forward every time you brake, and on the WRX the front brakes also do extra work for the Active Torque Vectoring system in corners. Plan on replacing front pads and rotors more often than rears, but measure both axles every time, because the rears can still surprise you.

How the 2015-2021 WRX Brake System Is Laid Out

The non-STI WRX uses disc brakes at all four corners. When Subaru introduced this generation for 2015, it called out larger front discs, now 12.4 inches in diameter (up from 11.6 inches on the previous WRX), for more swept area and better fade resistance. The front discs are ventilated, and the rears are a disc design as well. Subaru also fitted a new master cylinder for this generation.

This is a different system from the WRX STI. The STI of the same era uses a Brembo package with 13.0-inch front discs and 4-piston calipers, and 12.4-inch rear discs with 2-piston calipers. STI pads, rotors and calipers do not interchange with the standard WRX, so always shop by the exact model. Our 2015-2021 Subaru WRX (non-STI) front and rear brake kit is built for the standard car only.

Why the Front Brakes Wear First on a WRX

Three things push the WRX's wear toward the front axle:

• Weight transfer. When you brake, the car's mass pitches forward and loads the front tires. More grip at the front means the system is designed to have the front brakes produce most of the stopping force, so the front pads and rotors absorb most of the heat and wear.
• Active Torque Vectoring. Subaru describes this as a yaw-control system that uses the front brakes. When you corner, it applies slight pressure to the inside front brake to reduce understeer. That is a small amount of front-only brake use you never feel, repeated on every spirited corner, on-ramp and roundabout.
• Driving style. The WRX is built to be driven with some enthusiasm. Its 2.0-liter turbo engine makes 268 horsepower and 258 lb-ft of torque, and every burst of speed has to be scrubbed off by the brakes, mostly the fronts.

The rears are not immune. On an all-wheel-drive car with stability control, the system can brake individual wheels, and rear calipers that sit lightly used for long stretches in wet or salted climates are prone to sticking slide pins, which wears the inner rear pad quickly. That is why you measure all four corners, not just the fronts.

Symptoms and How to Tell Which End Needs Work

Most WRX brake complaints can be pinned to one axle with a short test drive and a look through the wheels.

• Squeal or scraping when braking: Subaru disc brakes use audible pad wear indicators, a metal tab that contacts the rotor and makes noise as the pad nears its service limit. Note which corner the sound comes from.
• Steering wheel shake under braking: almost always front rotors with uneven thickness or pad deposits. Rear rotor problems tend to show up as a pulse in the seat or pedal rather than the wheel.
• Pedal feels soft or goes lower than it used to: check the fluid level and condition first. The brake warning light on the dash is not a pad-wear light; it reports conditions such as low fluid or an applied parking brake.
• One wheel much dirtier than the others, or a hot smell from one corner: a dragging caliper. Pull that wheel and check the slide pins and pad movement.
• Grooved or lipped rotor face: run a fingernail across the rotor. A heavy lip or deep grooves mean the rotor should be replaced, not just the pads.

For a proper inspection, pull the wheels and look at the inner and outer pad on each caliper. Compare remaining lining thickness side to side and front to rear, and measure rotor thickness against the minimum stamped on the rotor.

What to Replace, and When

Front brakes

Most owners will do front pads at least once for every rear pad change. When you replace front pads, the rotors usually go with them on this car. The 12.4-inch fronts work hard and take heat from torque vectoring, and a fresh pad on a worn or glazed rotor is the most common cause of a new-brake shudder. Browse brake pads and brake rotors, or choose low-dust ceramic brake pads for a daily-driven WRX.

Rear brakes

Rear pads typically last longer, but check them every time the fronts are done. If the rears are near half their lining, a complete front and rear job now saves pulling the car apart again later. The WRX front and rear brake kit covers both axles in one order.

What to replace at the same time

• Hardware: new abutment clips and fresh caliper grease on the slide pins. Tired clips cause noise and uneven pad wear. See brake hardware kits.
• Brake fluid: brake fluid absorbs moisture over time. Flush it if it is dark or at the interval in your maintenance schedule, using only the fluid type shown on the reservoir cap and in the owner's manual.
• Calipers: replace a caliper that has a torn boot, a seized piston or a slide that will not free up with cleaning. Replace them in axle pairs. See brake calipers.

How Hard Is the Job?

A pad and rotor job on the WRX is a reasonable driveway project for someone with a floor jack, jack stands, a torque wrench and basic hand tools. The process is familiar: remove the caliper, hang it so the hose is not stretched, remove the bracket and rotor, clean the hub face, and reassemble with new parts. Torque every caliper, bracket and wheel fastener to the values in the factory service manual, and pump the pedal to seat the pistons before you drive.

After installation, bed the new pads before normal driving. Power Stop, for example, specifies a sequence of repeated stops from moderate speeds without cooling in between, followed by a cooling drive of about 5 minutes, and notes that proper bedding helps prevent rotor problems. Follow the procedure supplied with your pads.

A note on recalls: checking NHTSA's recall database for 2015 and 2016 WRX models, we found no recall for the friction brakes themselves (pads, rotors, calipers or hydraulics). One campaign covering some 2016 WRX cars did involve EyeSight: if the brake light switch failed, the automatic pre-collision braking would not function, and dealers reprogrammed the system. If your car has EyeSight, enter your VIN at nhtsa.gov to confirm that work is done.

Frequently Asked Questions

Do WRX front brakes really wear faster than the rears?

Yes. Forward weight transfer puts most of the braking load on the fronts, and the WRX's Active Torque Vectoring applies the inside front brake in corners. Expect to replace front pads more often than rear pads.

Can I use STI brake pads on my regular WRX?

No. The STI uses Brembo calipers with different rotor sizes and pad shapes. Buy parts listed for the non-STI 2015-2021 WRX.

Should I replace rotors every time I replace pads?

On the front of a WRX it is usually the right call, because the rotors see heavy heat. At the rear, reuse rotors only if they are above minimum thickness, flat, and free of heavy grooves or a lip.

Why does my WRX squeal from one corner only?

That is often the audible wear indicator on a pad nearing its limit. It can also be a sticking caliper slide making one pad wear faster. Pull the wheel and measure.

Does the brake warning light mean my pads are worn?

No. That light reports low fluid, a hydraulic issue or an applied parking brake. Pad wear is signaled by the audible indicator, so check the fluid first and have the system inspected if the light stays on.

Sources

1. Subaru U.S. Media Center - 2015 Subaru WRX debuts new level of performance - 12.4 in front discs, new master cylinder, Active Torque Vectoring uses front brakes, engine output
2. Subaru U.S. Media Center - 2015 Subaru WRX STI - STI Brembo system, 13.0 in fronts with 4-piston calipers, 12.4 in rears with 2-piston calipers
3. NHTSA recalls - 2015 Subaru WRX - no friction brake recall listed
4. NHTSA recalls - 2016 Subaru WRX - campaign 15V366000, EyeSight pre-collision braking and brake light switch
5. Power Stop - Z23 Evolution Sport brake kit - kit contents and pad bedding procedure