BMW 5 Series (G38) Big Brake Kit Upgrade / TTSPORT Classic 8703S
This BMW 5 Series, built on the G38 platform, came from the factory with a single-piston floating caliper up front — a setup that felt outmatched by the car's weight-reduced, high-strength chassis. To close that gap, the shop fitted a TTSPORT 8703S six-piston big brake kit, paired with 355mm high-carbon rotors, all tucked behind the car's stock 18-inch wheels.
The G38-generation 5 Series, released in spring 2017, uses carbon fiber, high-strength steel, and aluminum-magnesium alloy in its body structure — cutting up to 130kg versus the outgoing model. That lighter, stiffer chassis and the platform's healthy power output made the factory single-piston brake feel like the weak link, which is what pushed the owner toward a proper big brake kit.
Vehicle & Kit Specs
| Item | Specification |
|---|---|
| Vehicle | BMW 5 Series (G38 platform, long-wheelbase), fits behind 18-inch wheels |
| Stock brakes replaced | Factory single-piston floating caliper |
| Front caliper | TTSPORT 8703S cast six-piston caliper, one-piece cast design, yellow finish, integrated dust boots |
| Front rotor | TT 355x32mm high-carbon heat-treated slotted rotor with rust-resistant coating |
| Brake lines | TTSPORT stainless steel brake lines |
Why It Works
The 8703S is a one-piece cast caliper with six pistons clamping each rotor, replacing a single floating piston that flexes under hard braking and eats into pedal feel. More pistons spread clamping force evenly across the pad, so the pedal reads more consistent and less mushy. The dust boot design also keeps grit off the pistons and seals, which makes routine maintenance easier over time.
- Six-piston cast caliper distributes clamping force more evenly than the stock single-piston floating design.
- Larger 355x32mm rotor mass gives the system more surface area and heat capacity than the factory disc.
- Radial drilling on the TT rotor face aids heat dissipation, and the rust-resistant coating protects the areas the pads don't sweep.
- The kit clears the car's stock 18-inch wheels, so there's no wheel swap needed to run it.
- Stainless steel lines resist expansion under pressure, keeping pedal feel firm compared to stock rubber lines.
Installation Gallery
Frequently Asked Questions
What vehicle does this TTSPORT 8703S kit fit?
What's included in the TT8703S big brake kit?
What did this kit replace on the BMW 5 Series?
Need fitment confirmation? Choose the closest TTSPORT series or send your vehicle, wheel size, and intended use before ordering.