BMW 3 Series (G28) Big Brake Kit Upgrade / TTSPORT Slim SL6
There's a common assumption that a narrow, "slim" caliper can't be a serious brake caliper — that it's just a cosmetic compromise for people who don't want to run spacers. This BMW 3 Series (G28) build is a good counterpoint: a TTSPORT Slim SL6 six-piston kit, installed with zero clearance drama behind the car's stock 18-inch wheels, delivering a firmer, more linear pedal than the factory setup ever offered.
The goal behind the Slim SL6 design was straightforward: give owners who don't want to change wheels or add flange adapters a way to upgrade braking performance without the usual big-brake-kit compromises. No flange spacers, direct fitment on the original wheels, strong stopping power, a reasonable price, and a caliper that still fills out the wheel visually — that's the brief this kit was built to answer.
Vehicle & Kit Specs
Here's the hardware breakdown for this specific G28 3 Series install:
| Item | Specification |
|---|---|
| Vehicle | BMW 3 Series (G28), factory 18-inch wheels |
| Front caliper | TTSPORT Slim SL6 six-piston forged caliper |
| Front rotor | TTSPORT 355mm high-carbon, heat-treated rotor |
| Bracket | Custom vehicle-specific caliper bracket (steel) |
| Pads / lines | TTSPORT high-performance street pads, TTSPORT stainless brake lines |
| Hardware | Brake fluid, mounting bolts, and fixing hardware |
The table below is TTSPORT's official spec sheet for the SL6 caliper used in this kit:
| Brake Caliper | |
|---|---|
| Series | Slim Series |
| Model / Application | SL6 |
| Axle Position | Front |
| Piston Count | 6-piston |
| Piston Type | One-piece heat-insulated pistons |
| Piston Diameter | 28 mm × 2 / 30 mm × 2 / 36 mm × 2 |
| Caliper Dimensions | L 350 mm × W 135 mm × H 120 mm |
| Total Piston Area | 46.8 cm² per caliper, all pistons combined |
| Manufacturing Process | Two-piece forged aluminum body |
| Net Weight | 3.60 kg per caliper, without pads |
| Surface Finish | High-temperature gloss coating |
| Recommended Wheel Size | 17 in or larger |
| Recommended Rotor Size | Ø330–355 mm × 28 mm |
| Fitment & Installation | |
| Minimum Spoke Clearance (mm) | 82 |
| 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 SL6 is a two-piece forged caliper with a through-bolt tie rod connecting the two halves, which stiffens the body and cuts down the flex you get in a thin-walled factory caliper under hard braking. That rigidity is what turns pedal travel into actual clamping force instead of caliper deflection — it's the difference between a mushy pedal and one that feels planted.
- Direct fitment on 17-18 inch wheels — no flange adapters or spacers needed, so ride geometry stays stock.
- Differential-bore six-piston layout applies clamping force more evenly across the pad, giving a more linear, controllable brake feel.
- Extensive lightening cutouts in the caliper body improve airflow around the pistons, helping manage heat buildup and reduce fade on repeated stops.
- The 355mm high-carbon, heat-treated rotor adds thermal capacity and wear resistance over the factory disc, which should help the whole system hold up better over time.
At 350mm long, 135mm wide, and 120mm tall, the SL6 also fills the wheel opening noticeably better than the stock caliper — the fitment upgrade doesn't come at the cost of looking undersized behind the spokes.
Installation Gallery
Frequently Asked Questions
Does the TTSPORT SL6 kit fit BMW 3 Series (G28) factory wheels without spacers?
What rotor size does this BMW 3 Series kit use?
What's included in the TTSPORT SL6 kit besides the caliper and rotor?
Need fitment confirmation? Choose the closest TTSPORT series or send your vehicle, wheel size, and intended use before ordering.