Hella 355123172 Disc Brake Rotor 298mm Solid

This is the Hella 355123172, a solid one-piece disc brake rotor cast from gray iron and finished with a zinc coating. It's a straightforward replacement rotor built to a set of fixed dimensions, so if your current rotor matches this size and pattern, it drops right into the same spot on the hub. No vents, no two-piece hardware, just one clean casting that does its job.

The numbers matter on a brake rotor, so here they are up front. The outside diameter is 298 millimeters. Nominal thickness is 16 millimeters. Overall height, measured from the friction face to the back of the hat, is 71 millimeters. The center hub bore is 85 millimeters, and the wheel bolt pattern is 7 x 130 millimeters. Those five measurements are what determine fitment, and all five have to match your vehicle before this rotor is the right part. Cross-reference the part number 355123172 and the dimensions against your application before you order.

Solid rotors like this one are common on lighter-duty and rear positions where the brakes don't shed as much heat as a heavy front setup. There's no internal vane structure, so the casting is a single slab of iron between the two friction faces. That keeps it simple and keeps the cost down. It also means the whole rotor is one continuous piece, which is easy to inspect and easy to measure for wear.

The zinc coating is there for corrosion resistance. It protects the hat, the edges, and the non-swept areas that would otherwise flash-rust the first time the vehicle sits out in the weather. The coating on the actual braking surface wears away in the first few stops once the pads start sweeping the face, and that's normal. You'll see a bright ring form where the pad rides. The zinc keeps the rest of the rotor looking clean and slows the surface rust that makes a rotor look tired long before it's actually worn out.

Gray cast iron is the standard material for a reason. It handles heat well, it wears predictably against a standard brake pad, and it damps vibration so you get quiet, consistent braking. Cast iron does have a limit, though. If you cook a rotor hard enough, on a long grade or with a dragging caliper, a solid one-piece casting can warp or develop hot spots. That's true of any rotor in this class, so keep an eye on your brake temps if you're working the vehicle hard.

On wear, the 16 millimeter figure is the nominal new thickness. Every rotor has a minimum thickness cast or stamped into the hat, and that's the number that actually matters when you're deciding whether to reuse or replace. Measure across the swept area with a micrometer. If you're at or below the stamped minimum, the rotor is done. Don't machine a rotor past its minimum to save it, because a thin rotor holds less heat and is more likely to warp.

Replace rotors in pairs across an axle whenever you can. Even if only one side is worn, a fresh rotor on one corner and a tired one on the other gives you uneven braking feel, and it can pull the vehicle under hard stops. New rotors also want fresh pads and a proper bed-in. Bedding seats the pad material evenly onto the new surface and sets you up for quiet, full-strength braking from the start.

Installation is simple if you take your time. Clean the hub mating surface down to bare metal so the rotor seats dead flat. Any rust scale or old debris under the rotor throws off runout and gives you a pulsing pedal. Slide the rotor on, run the wheel down, and torque the lug nuts to your vehicle manufacturer's spec in a star pattern. Over-torquing or an uneven pattern can distort the rotor and undo all your careful prep.

This rotor is sold as a single piece, one rotor per box. If you're doing both sides of an axle, order two. It's a fit-and-forget part when it's matched correctly and installed clean, which is exactly what you want out of a brake component you're trusting to stop the vehicle.