Hella 355122472 Vented Brake Rotor 300mm 7x112

The Hella 355122472 is a vented disc brake rotor machined from gray cast iron and finished with a zinc coating. It's a one-piece design, so the hat and the braking surface are cast as a single unit. That keeps things simple at install and cuts out the runout problems you can get with two-piece assemblies that aren't torqued right. This one measures 300mm across the outside diameter with a 28mm nominal thickness, and it carries a 7 x 112mm wheel bolt pattern with a 67mm hub size.

The vented face is doing real work here. Between the two braking surfaces sit cast cooling fins that pull air through as the wheel spins. Heat is the enemy of any brake system. Under hard, repeated stops, a solid rotor soaks up temperature and hangs onto it, and that's when you start to feel fade at the pedal. A vented rotor sheds that heat faster, so the pad and disc stay in their happy range longer. If you tow, run hills, or just ride the brakes in traffic more than you'd like, venting matters.

The zinc coating is about corrosion. Bare cast iron flash-rusts almost the moment it's exposed to moisture, and while the braking surface wears clean every time you use it, the hat, the edges, and the vanes don't. Left uncoated they turn orange and ugly, and the rust can creep. The zinc finish keeps the non-wear areas looking clean and slows down the corrosion that eats at a rotor sitting through a wet season. It's a fit-and-forget touch that pays off a couple years down the road.

Gray cast iron is the standard rotor material for a reason. It damps vibration well, machines cleanly, and handles the thermal cycling a brake rotor lives through better than most alternatives. Hella casts this one as a single piece and holds the tolerances tight, so you're not chasing pedal pulsation from an out-of-spec disc. The 46.30mm overall height and the 67mm hub bore are the numbers that decide whether it sits flat and centered on your hub.

Fitment on a brake rotor comes down to a handful of measurements, and they all have to match. Start with the bolt pattern, a 7 x 112mm here. Then the outside diameter at 300mm and the nominal thickness at 28mm. Check the hub bore too, 67mm, since that's what centers the rotor on the hub. The easiest way to be sure is to pull your old rotor and measure it, or match the numbers against your vehicle's brake specs. If all of those line up, you're good. If any one of them is off, keep looking, because a rotor that's close but not exact will give you grief.

This part is sold as a single rotor. Standard practice is to replace rotors in axle pairs, left and right together, so both sides wear and heat evenly and the vehicle stops straight. Plan on ordering two if you're doing a full axle. And whenever you put fresh rotors on, do the pads at the same time and bed them in properly. New pads on a glazed or grooved disc never seat right.

One thing worth knowing before you install: don't paint or coat the actual braking surfaces yourself. The factory zinc finish is set up to wear off cleanly where the pad rides while staying put on the vanes and hat, and that happens in the first few stops. That's normal. You want bare, clean metal where the pad makes contact.

Installation is straightforward for anyone who's done a brake job. Wipe the protective film off the braking surfaces with brake cleaner before the pads touch the disc, torque the caliper hardware to spec, and take it easy for the first few stops while everything beds in. If you've got the tools and an afternoon, this is a very doable job. If brakes aren't your thing, any shop can install it. Either way, you're getting a corrosion-resistant, properly vented replacement rotor built to a real set of dimensions.