BRZ / FR-S / 86 Front Big Brake Kits: PA055 4-Piston vs PA015/PA035 6-Piston

The Paragon PA055 4-piston kit is the sharper value for drivers on stock or near-stock 17-inch wheels who want a proven, endurance-tested front brake upgrade with a 330 mm floating rotor. The Paragon PA015/PA035 6-piston kit steps up to three staggered-bore pistons per side, rotor choices up to 370 mm, and greater thermal mass; the right choice for builders running 18-inch or larger wheels who want the most headroom on repeated hard laps. Both bolt on without touching the OEM ABS or rear brakes.

Spec Comparison

Piston diameters for the PA055 are sourced from Paragon rebuild kit PCS.06.JK.PK.01; confirm your exact bore layout with Paragon for the BRZ application. Piston diameters for the PA015/PA035 are sourced from rebuild kit PCS.02.CEJ.PK.01.

PA055 4-Piston: Track-Proven, 17-Inch Friendly

The PA055 is built around a single, purpose-matched rotor size for the BRZ/FR-S/86 platform: 330 mm in diameter by 28 mm thick. That is a meaningful step up from the OEM 1-piece 293 mm vented rotor, adding both swept area and thermal mass without demanding a wheel upgrade. Paragon's catalog notes that the same PA055 calipers are used by Team Honda Research West in their 25 Hours of Thunderhill 11th-gen Civic Si endurance cars, which tells you something about how the caliper holds up under sustained abuse.

Each caliper weighs 5.4 lbs. The two staggered piston bores (38.1 mm and 41.3 mm) are sized to work with the OEM master cylinder and ABS without adjustment. The fully-floating 2-piece rotor uses Paragon's CM-250 high carbon alloy cast iron friction ring on a hard-anodized 6061-T6 hat with stainless steel bobbins and anti-rattle clips. Goodridge DOT-approved stainless braided lines and a caliper mounting bracket pair are included; the Paragon P3 Street/Track semi-metallic pads (made by Winmax Japan) come standard, with other compounds available at additional cost.

Who it's for: Drivers on 17-inch wheels who want a no-compromise track kit without buying new wheels. Also a strong pick for HPDE regulars, autocross competitors, or anyone who wants the visual and functional upgrade without stepping into a larger rotor package. If your car still runs OEM wheels, this is likely your direct path to a bolt-on, tested front brake upgrade.

Honest trade-offs: The 330 mm rotor is the only option for this fitment. There is no larger rotor configuration published for the PA055 on this platform, so if your build evolves toward time attack and you later want 355 mm or more, you would be looking at a caliper change. The kit is also listed as made to order, so plan lead time into your schedule.

PA015/PA035 6-Piston: More Rotor, More Options, More Wheel Required

The PA015/PA035 kit centers on the same billet 6061-T6 aluminum caliper body, but with three staggered piston bores per side: 27 mm, 31.8 mm, and 38.1 mm. The PA015 and PA035 are the same physical caliper; the PA035 designation accommodates the larger 370 mm rotor. Three rotor configurations are offered: 343 mm x 32 mm (48-vane), 355 mm x 32 mm (72-vane), and 370 mm x 36 mm (72-vane). Every step up in rotor size adds more swept area, more thermal mass, and more vane count for heat rejection on long, aggressive sessions.

Each caliper comes in at 6.5 lbs. The same fully-floating 2-piece rotor construction applies here: CM-250 high carbon iron ring, hard-anodized aluminum hat, stainless bobbins. Goodridge DOT SS braided lines and mounting brackets are included. The kit ships with the same Paragon P3 Street/Track pads, and the PA015/PA035 caliper family supports a wider named compound range including R5 and R7 competition-grade options.

Paragon publishes a 6-piston kit for the BRZ/GR86/86 specifically (the same SKU base as the WRX fitment listed here), and the 343 mm entry-level configuration clears 17-inch wheels. Move to the 355 mm or 370 mm rotor and you need 18 inches or larger. On the WRX fitment page, Paragon confirms fitment of the 343 mm rotor with Apex SM-10RS 17x10 +45 wheels as a real-world reference point.

Who it's for: Builders who already run or plan to run 18-inch track wheels, drivers doing repeated hot sessions where the 330 mm rotor's smaller thermal mass could be a limiting factor, and anyone who wants the visual presence of a 6-piston setup with the flexibility to scale up rotor size as the build grows. The step from the 343 mm entry option to the 355 mm or 370 mm configurations is a genuine performance upgrade path, not just a cosmetic one.

Honest trade-offs: The 355 mm and 370 mm configurations require 18-inch or larger wheels, so if you run the OEM 17-inch setup, your only 6-piston entry point is the 343 mm kit. The caliper is 1.1 lbs heavier per side than the PA055. If you are on stock wheels and doing occasional track days rather than sustained competitive sessions, the added complexity and cost over the PA055 may not return a noticeable difference in braking performance on the BRZ platform.

How to Choose

Start with your wheels. If you are on 17-inch wheels and plan to stay there, the PA055 4-piston kit is the clear fit: it was engineered specifically for this platform, clears OEM-size wheels, and brings a meaningful rotor size increase from the stock 293 mm to 330 mm. If you are already running 18-inch or larger track wheels, the 6-piston kit opens up rotor options up to 370 mm x 36 mm and gives you more surface area and thermal capacity to work with.

Next, consider how hard you push the car. For HPDE days, autocross, and occasional sprint sessions, the PA055 is more than capable. For time attack, endurance laps, or repeated hard sessions where sustained heat management matters, the larger rotor options in the 6-piston kit earn their place.

Either way, both kits retain OEM ABS function, work alongside the stock rear brakes, and include Goodridge braided lines and a caliper mounting bracket. Neither requires a master cylinder change. The decision comes down to what your wheels permit and how deep into competition driving your build is headed.

For more on how this PA055 vs. PA015/PA035 decision plays out on another platform, see our EVO X front big brake kit comparison. For GR86-specific brake context, the GR86 mid-cycle refresh brake overview is worth a read before you finalize your setup.