Hella 355122532 Vented Brake Rotor 300mm 6x112 67mm Hub

The Hella 355122532 is a vented disc brake rotor for passenger-vehicle disc brakes, and it's the kind of part you want to get right the first time. Brakes aren't where you cut corners. This one is a one-piece casting in gray cast iron with a zinc coating on the non-friction surfaces, so it fights the surface rust that makes a rotor look ugly on the shelf and streaks your wheels after the first wet drive.

Let's talk dimensions, because with a rotor the numbers are everything. This one runs 300 millimeters across the outside diameter, 22 millimeters of nominal thickness, and stands 68.20 millimeters tall. It uses a 6 x 112 millimeter wheel bolt pattern and seats on a 67 millimeter hub bore. Those figures match a lot of European passenger cars, and the 6 x 112 pattern with a 67mm center bore is a signature of many Mercedes-Benz applications. Before you order, cross-check the part number against your year and model, because a rotor that's a millimeter off in thickness or bolt circle simply won't work.

The vented design is the important bit. A vented rotor has two friction faces separated by internal vanes that pump air through the disc as the wheel turns. That airflow pulls heat out of the casting, which matters any time you're braking hard and often, like a long grade with a loaded car or stop-and-go on a hot day. Heat is the enemy of braking. Let a rotor cook and you get brake fade, that soft pedal feeling when the pads and disc get too hot to bite. The 22mm thickness here gives the vanes room to move air and gives the rotor enough mass to soak up heat between stops.

Gray cast iron is the standard material for a reason. It handles heat well, it damps vibration so you get less squeal, and it wears in a predictable way against the pad. The zinc coating is there for the parts of the rotor you don't want rusting: the hat, the edges, the vent gaps. The friction faces will clean themselves off with the first few stops as the pads scrub the coating away, which is normal and exactly what you want.

This rotor is sold as a single. Good practice is to replace rotors in axle pairs, both fronts or both rears together, so the car brakes evenly side to side. If you're doing a brake job, plan on fresh pads at the same time. New pads on a worn rotor, or an old glazed pad on a fresh rotor, never bed in cleanly and you'll hear about it. Order two of these for the axle, grab your pads and hardware, and do the job once.

Install is straightforward for anyone who's turned a wrench on brakes. Pull the caliper and bracket, slide the old rotor off, and clean the hub face down to bare metal so the new rotor sits flat. Any rust or crud on the hub throws off runout and gives you a pulsing pedal down the road. A dab of anti-seize on the hub register, not the friction face, keeps the next rotor from fusing on. Torque the caliper bracket to spec, fit your pads, and pump the pedal up before you roll.

Bedding in matters. Once it's on, find a safe stretch of road and make a series of moderate-to-firm stops from speed, easing off before you come to a full halt, then let the brakes cool. This transfers an even layer of pad material onto the disc and sets up smooth, quiet braking. Skip it and you risk uneven deposits that show up as a shudder later.

Who's this for? Anyone replacing worn or warped rotors on a vehicle that runs the 6 x 112mm pattern and a 67mm hub. It's a straight replacement-grade part with the vented cooling and corrosion-resistant coating you'd expect from Hella. It's not a drilled or slotted performance rotor, and it doesn't need to be for daily driving. What it does is give you a clean, true friction surface and reliable stopping, which is exactly what a brake rotor is supposed to do. If your part number matches, it's an easy call.