Smart #3 Big Brake Kit Upgrade / TTSPORT Slim SL8
Smart's #3 isn't the city runabout the badge used to mean. With dual-motor versions pushing well past 400 horsepower and 0-60 in the mid-3-second range, the platform has more mass and more speed to shed than the stock brakes were ever designed for. This case covers a full front-and-rear TTSPORT big brake kit built to catch up with that performance.
EVs like the #3 carry a heavier curb weight than comparable gas cars, often by 400-plus pounds, once the battery pack is factored in. That extra mass doesn't matter much in daily commuting, but it shows up fast on a long downhill, a series of hard highway stops, or a track day — the stock brakes lose pedal firmness and stopping consistency as they heat up. Brakes are typically the first thing worth upgrading on a car like this, before touching the powertrain at all.
Vehicle & Kit Specs
The build runs a front TTSPORT SL8 eight-piston caliper with a 405mm rotor, paired with a TTSPORT EP4 electronic parking brake caliper and 380mm rotor at the rear — a front-eight, rear-four layout matched to the car's factory 20-inch wheels.
| Item | Specification |
|---|---|
| Vehicle | Smart #3, 20-inch wheels |
| Front caliper | TTSPORT SL8 forged eight-piston caliper |
| Front rotor | TTSPORT 405mm two-piece rotor |
| Rear caliper | TTSPORT EP4 electromechanical (EPB) caliper |
| Rear rotor | TTSPORT 380mm two-piece rotor |
| Bracket | Vehicle-specific caliper brackets, front and rear |
| Pads / lines | TTSPORT high-performance brake pads, stainless steel brake lines |
| Hardware | Brake fluid, mounting bolts, and fitting hardware |
The front caliper in this kit is the TTSPORT SL8 from the Slim Series; the full spec sheet is below.
| Brake Caliper | |
|---|---|
| Series | Slim Series |
| Model / Application | SL8 |
| Axle Position | Front |
| Piston Count | 8-piston |
| Piston Type | One-piece heat-insulated pistons with dust boots |
| Piston Diameter | 28 mm × 4 / 32 mm × 4 |
| Caliper Dimensions | L 391 mm × W 128 mm × H 144 mm |
| Total Piston Area | 56.8 cm² per caliper, all pistons combined |
| Manufacturing Process | Two-piece forged aluminum body |
| Net Weight | 5.20 kg per caliper, without pads |
| Surface Finish | High-temperature gloss coating |
| Recommended Wheel Size | 19 in or larger |
| Recommended Rotor Size | Ø380–405 mm × 34 mm |
| Fitment & Installation | |
| Minimum Spoke Clearance (mm) | 90 |
| 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
Front-eight, rear-four is a well-proven layout for cars in this weight and power class. The front axle does most of the braking work under load, so it gets the larger caliper and rotor; the rear stays lighter and simpler. Spreading clamping force across eight pistons instead of one or two sliding pins means more even pad contact and a caliper body stiff enough to resist flex under heat and repeated hard stops — that's what keeps the pedal feeling consistent instead of going soft after a few hard applications.
- Forged two-piece SL8 body resists flex for a firmer pedal under repeated hard braking
- 405mm front rotor adds mass and swept area to absorb heat on long descents or track sessions
- Vehicle-specific brackets clear the factory 20-inch wheel with no spacers required
The rear EP4 matters just as much on an EV like this. Because it's built as an electromechanical caliper, it works directly with the Smart #3's factory electronic parking brake rather than replacing it with an aftermarket workaround — the stock ECU logic and safety functions stay intact after the swap.
Installation Gallery
FAQ
Does the TTSPORT EP4 rear caliper work with the Smart #3's electronic parking brake?
What wheel size does this kit fit under?
What's included in the kit besides the calipers and rotors?
Need fitment confirmation? Choose the closest TTSPORT series or send your vehicle, wheel size, and intended use before ordering.