Quick Info
Model
450, 451, 452
Estimated Cost
100-200€
Difficulty
Intermediate
Time Required
1 Hour
Safety Notes
Proper Jacking: Always secure the vehicle on heavy-duty jack stands. Never rely on the hydraulic jack alone while removing braking components.
Torque Specifications: The caliper carrier bolts (E18) are critical safety fasteners and must be torqued to 150 Nm.
Brake Cleaner Mandatory: New discs are often coated in protective oil. You must thoroughly clean the disc surface with brake cleaner before installing the pads to ensure immediate stopping power.
Pedal Priming: After reassembly, you must pump the brake pedal several times while the engine is running to seat the pads against the discs before moving the car.
Bedding-In Period: Avoid heavy or emergency braking for the first 200–300 km to allow the new pads and discs to "bed in" properly and avoid glazing.
Step-by-Step Guide
Introduction
The factory braking system on the Smart Roadster (452) and Fortwo (450) is functional, but for those who enjoy spirited driving or track days, heat soak can quickly lead to "brake fade." Standard solid discs struggle to dissipate heat under repeated heavy braking, which can lead to a soft pedal and increased stopping distances.
Upgrading to Zimmermann Drilled Brake Discs is the ultimate solution for consistent performance. These discs are engineered with high-carbon steel for better thermal stability and feature a signature drilled pattern that allows gases and heat to escape more efficiently. Not only do they provide a significant boost in "initial bite" and cooling, but they also give your Smart a premium, high-performance look behind the wheels.
This guide walks you through the professional installation of a Zimmermann brake kit. We cover everything from checking your brake fluid water content to the heavy-duty torquing required for the calipers—ensuring your Smart stops just as fast as it goes.
Preparation & Brake Fluid Test
Park on a level surface and loosen the wheel bolts. Jack up the car and secure it on stands. Before starting the mechanical work, use a Brake Fluid Tester to check the moisture content in your reservoir. If it shows high water percentage, plan for a full system bleed after the hardware install. Remove the wheels and open the brake fluid reservoir cap to make compressing the pistons easier later.
Caliper & Pad Removal
Use a 13mm wrench and 17mm counter-hold wrench to remove the lower caliper slider bolt. Swing the caliper upward to access the old pads. Use a flathead screwdriver or brake tool to gently push the piston back into the caliper body. Slide out the old pads, noting the position of the metal clip on the inner pad.
Caliper Carrier Removal
To remove the disc, you must take off the caliper carrier. Use an E18 External Torx socket to remove the two large bolts behind the hub. Once free, use a zip tie to hang the caliper assembly from the suspension spring; never let it hang by the rubber brake line as this can cause internal damage.
Disc Swap & Hub Cleaning
Remove the small T30 Torx screw holding the disc to the hub. If the disc is stuck, use a hammer to tap the center area until it breaks free. Once the old disc is off, use a wire brush to clean the hub surface thoroughly. Apply a thin layer of copper grease to the hub to prevent future seizing, then slide on the new drilled Zimmermann disc and secure it with the T30 screw.
Reassembly & Final Torque
Reinstall the caliper carrier and tighten the E18 bolts to 150 Nm. Install the new pads (inner pad has the clip) and apply a small amount of copper grease to the outer edges where they touch the caliper. Swing the caliper back down and tighten the 13mm slider bolt to 35 Nm. Clean the disc with brake cleaner, reinstall the wheel, and pump the brake pedal several times before driving.
