Hella 355117832 300mm Vented Disc Brake Rotor 6x120

Brake rotors are one of those parts you don't think about until the pedal starts pulsing or you hear a grind coming into a stop. This Hella 355117832 disc brake rotor is a straight replacement casting, built to get a worn corner back to solid, quiet, predictable stopping. It's a vented one-piece rotor measuring 300 millimeters across, 20 millimeters thick, with a 66 millimeter overall height and a 6 x 120 millimeter wheel bolt pattern. If those numbers match what's on your car right now, this is the part that bolts on.

The vented design is the important bit here. Instead of a single solid disc, a vented rotor has two friction faces with cooling vanes cast between them. Air pulls through those vanes as the wheel spins and carries heat away from the braking surface. That matters because heat is what kills braking performance. Push a solid rotor hard on a long downhill or in stop-and-go traffic and it soaks up heat until the pads start to fade. A vented casting sheds that heat far better, so you keep a firm pedal and consistent bite when you're leaning on the brakes.

It's a one-piece casting in gray cast iron, still the material of choice for daily-driver brake rotors for good reason. Gray iron handles repeated heat cycles without the warping you'd worry about with cheaper metals, and it machines to a smooth, even friction face that treats your pads kindly. The one-piece construction means the hat and the disc are cast as a single unit, so there's nothing to come loose and no extra assembly to fuss with at install.

Hella finishes this rotor with a zinc coating, and if you've ever pulled a wheel after a wet winter and found the rotor hat and edges caked in orange rust, you'll appreciate it. The zinc holds off surface corrosion on the areas the pads never touch, so the rotor keeps looking clean behind an open-spoke wheel and the hat doesn't seize onto the hub over time. The coating on the friction face itself wears away in the first few stops as the pads seat, which is completely normal and exactly what's supposed to happen.

A rotor only does its job if the dimensions match, so check your numbers before you order. Outside diameter here is 300 millimeters, nominal thickness is 20 millimeters, and the bolt pattern is 6 x 120 millimeter. Thickness in particular is worth confirming against your caliper and pads, because a rotor that's even a couple millimeters off won't sit right in the caliper. When in doubt, measure the rotor that's coming off, or match it against your vehicle's service spec.

This is sold as a single rotor, so if you're doing both sides of an axle, which we'd always recommend, order two. Replacing rotors in pairs keeps braking even side to side and stops the car from pulling under hard braking. It's also the right time to put fresh pads on. New pads on a new rotor bed in together and give you the cleanest, quietest result. Putting worn pads onto a new rotor just transfers the old uneven deposits and can leave you with the noise or vibration you were trying to get rid of.

Install is straightforward if you've turned a wrench before. Clean the hub face so the new rotor sits flat, hang it, torque your caliper bracket and wheel to spec, then bed the brakes in properly before you drive normally. A typical bed-in is a series of moderate stops from around 35 to 5 miles per hour, backing off between them to let things cool, which lays down an even layer of pad material and sets up smooth, quiet braking. Skip that step and you're more likely to end up with pedal pulsation down the road. And if brake work isn't your thing, any shop can install it in well under an hour.