BMW i4 Big Brake Kit Upgrade / TTSPORT Classic 8657S
The BMW i4 pairs a coupe-like silhouette with instant EV torque, but that extra weight and quick-off-the-line acceleration put real strain on the factory brakes. One i4 owner ran into exactly that problem and swapped the stock front setup for a TTSPORT Classic Series 8657S six-piston big brake kit.
Several i4 owners have flagged the same two complaints with the factory binders: a rattle or squeal at low speed and light pedal pressure, and noticeable fade — softer pedal, less bite — after hard or repeated stops. Neither is unusual for an OEM caliper asked to manage a heavier EV chassis, but both get old fast if you actually drive the car.
The owner landed on TTSPORT, a domestic performance brake brand with more than 20 years in both racing and street applications, and picked the Classic Series 8657S — a forged six-piston caliper built for exactly this kind of mid-size, high-output application.
Vehicle & Kit Specs
| Item | Specification |
|---|---|
| Vehicle | BMW i4, 19-inch wheels |
| Front caliper | TTSPORT 8657S forged six-piston fixed caliper |
| Front rotor | TTSPORT 380mm high-carbon rotor |
| Bracket | Vehicle-specific caliper bracket |
| Pads / lines | TTSPORT high-performance pads, stainless steel brake lines |
| Hardware | Brake fluid, mounting bolts and hardware |
Here are the full manufacturer specs for the 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 |
Why It Works
- The 8657S body is forged in two pieces and finish-machined with a hollowed-out design, so it stays rigid under load instead of flexing — that rigidity is what gives the pedal a firmer, more linear feel compared to a stock sliding caliper.
- The progressive six-piston layout (two pairs of increasing diameter) spreads clamping force more evenly across the pad, which helps deliver a controllable, predictable bite rather than an on/off grab.
- Two-piece heat-insulated pistons with dust boots and high-temperature seals keep heat from migrating into the brake fluid during repeated hard stops, directly addressing the fade the owner had been dealing with.
- Stepping up to a 380mm rotor adds swept area and thermal mass over the factory disc, giving the system more capacity to absorb and shed heat before fade sets in.
Installation Gallery
What brake problems did this BMW i4 have before the upgrade?
What TTSPORT kit was installed on the i4, and what does it include?
Does the 8657S kit fit behind the i4's factory wheels?
Need fitment confirmation? Choose the closest TTSPORT series or send your vehicle, wheel size, and intended use before ordering.