Audi TTRS 8J brake system – Golf 5 GTI / S3 / RS3 / Big Brake Kit
Upgrading the braking performance on the VAG PQ35 platform (Golf 5 GTI, S3 8P) using the Audi TTRS 8J (4-piston Brembo) setup is one of the most popular “OEM+” modifications. It offers a significant increase in thermal capacity and clamping force without the complexity of aftermarket race kits.
The TTRS 8J Brembo Setup
The TTRS 8J front system utilizes a fixed 4-piston aluminum monoblock caliper manufactured by Brembo, paired with a massive 370mm rotor.
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Caliper Type: Brembo 4-piston Monoblock.
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Rotor Size: $370\text{mm} \times 32\text{mm}$.
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Piston Diameters: Staggered diameters to ensure even pad wear and modular pedal feel.
Compatibility & Fitment Guide
| Vehicle Model | Fitment Notes |
| Golf 5 GTI / Edition 30 | Direct bolt-on to the hub, but requires TTRS-specific brake lines. |
| Audi S3 (8P) | Direct bolt-on. Uses the same aluminum knuckles as the TTRS, making alignment perfect. |
| Audi RS3 (8P) | This is the factory setup. Upgrading usually involves moving to the 8V (newer) 370mm wavy rotors. |
1. The “Knuckle” Factor
The TTRS calipers bolt directly to the aluminum steering knuckles found on the S3, Leon Cupra R, and TTRS. If you have a standard Golf 5 GTI with cast iron knuckles, the calipers will still bolt up, but you must ensure you are using the correct carrier bolts ($M14 \times 1.5$).
2. Wheel Clearance (The Biggest Hurdle)
The 370mm rotor and the profile of the Brembo caliper are very wide.
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Minimum Diameter: 18-inch wheels are mandatory.
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Offset (ET): Most OEM 18″ wheels (like the Monza/Detroit) will not clear the face of the caliper. You will likely need 8mm to 12mm spacers or wheels with a lower offset (ET35-45) and “BBK-friendly” spoke designs.
3. Master Cylinder Considerations
Moving from a single-piston sliding caliper (GTI/S3) to a multi-piston fixed caliper changes the pedal stroke.
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The S3/TTRS 23.8mm master cylinder is usually sufficient to maintain a firm pedal.
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If installing on a standard GTI, the pedal may feel slightly “longer” or softer initially unless the system is bled perfectly using a pressure bleeder and VCDS to cycle the ABS pump.
Recommended Components for the Swap
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Rotors: * OEM TTRS: Heavy, but reliable.
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034Motorsport / RacingLine 2-Piece: Significantly reduces unsprung weight to per side) and improves cooling.
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Brake Lines: You cannot reuse GTI lines. You need TTRS-specific stainless steel braided lines with the correct banjo fitting for the Brembo caliper.
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Pads: * Street: Ferodo DS2500 (great cold bite, low noise).
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Track: Pagid RS29 or Endless ME20.
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