BMW Z4 Big Brake Kit Upgrade / TTSPORT Classic 8657S
Push a BMW Z4 hard on track days and the stock brakes start to fade fast — pedal travel grows, feedback goes soft, and stopping distances stretch out right when you need them most. This Z4, built by CSRC, addressed that with a TTSPORT Classic Series 8657S big brake kit up front and matching oversized rotors in back.
The car runs 19-inch wheels, which left enough room for a real six-piston caliper and a larger rotor without spacers or wheel changes — the goal of an OEM+ upgrade like this one.
Vehicle & Kit Specs
Here's the hardware breakdown for this Z4 build:
| Item | Specification |
|---|---|
| Vehicle | BMW Z4, 19-inch wheels |
| Front caliper | TTSPORT Classic Series 8657S six-piston caliper |
| Front rotor | TTSPORT 380mm high-carbon heat-treated rotor |
| Rear rotor | TTSPORT 355mm high-carbon oversized rotor |
| Bracket | Custom vehicle-specific caliper bracket |
| Pads / lines | TTSPORT high-performance street pads, stainless steel brake lines |
| Hardware | Brake fluid, mounting bolts, and fasteners |
Below is the official spec sheet for the TTSPORT 8657S caliper used in this build.
| Brake Caliper | |
|---|---|
| Series | Classic Series |
| Model / Application | 8657S |
| Axle Position | Front |
| Piston Count | 6-piston |
| Piston Type | Two-piece heat-insulated pistons with dust boots |
| Piston Diameter | 30 mm × 2 / 34 mm × 2 / 38 mm × 2 |
| Caliper Dimensions | L 350 mm × W 165 mm × H 92.64 mm |
| Total Piston Area | 55.0 cm² per caliper, all pistons combined |
| Manufacturing Process | Two-piece forged aluminum body |
| Net Weight | 4.05 kg per caliper, without pads |
| Surface Finish | High-temperature gloss coating |
| Recommended Wheel Size | 18 in or larger |
| Recommended Rotor Size | Ø355–405 mm × 32–34 mm |
| Fitment & Installation | |
| Minimum Spoke Clearance (mm) | 107 |
| Caliper Mounting Type | Radial mount with vehicle-specific caliper brackets |
| Brake Line Fitting Type | Vehicle-specific fittings; caliper-side and chassis-side fittings vary by application |
The 8657S is a step up from the previous-generation TT8657, revised at the piston, caliper venting, and overall size level.
Why It Works
- Two-piece forged aluminum caliper body — high strength with less mass, which cuts unsprung weight and helps keep the caliper rigid under hard braking loads instead of flexing and eating pedal travel.
- Two-piece vented pistons resist deformation and heat soak better than single-piece pistons, which keeps the caliper's clamping behavior consistent lap after lap.
- Progressive six-piston clamping delivers a linear, predictable pedal — the front pistons apply force in stages rather than all at once, so modulation stays smooth whether you're driving to the store or braking hard into a corner.
- A larger rotor — 380mm front, 355mm rear — adds swept area and thermal mass, which means more consistent stopping power and less fade as brake temperatures climb during repeated hard stops.
Installation Gallery
FAQ
What brake kit did this BMW Z4 install for track and spirited driving?
What's included in the TTSPORT 8657S big brake kit for the Z4?
What rotor sizes can be used with the TTSPORT 8657S caliper?
Need fitment confirmation? Choose the closest TTSPORT series or send your vehicle, wheel size, and intended use before ordering.