Where is rotor size stamped?
Rotor size is typically stamped directly on the rotor itself—often on the face near the center hub or along the outer edge—though some rotors carry the size or a part number only on packaging or in the vehicle’s service manual.
Common stamping locations
Rotors come in a variety of designs, and the markings can appear in several standard spots. The following list highlights the places where you’re most likely to find size information stamped or etched on the rotor or its accompanying parts.
- On the rotor face near the edge: Many rotors have diameter and thickness markings along the outer circumference or near the vent slots on the smooth facing side.
- On the rotor hub or center bore area: Some rotors stamp size information around the inner hub surface where the rotor mounts to the wheel hub.
- On the rotor hat or behind the cooling vanes: The central “hat” region can carry size data or a size-related part number.
- In embossed or laser-etched markings: Some rotors use etched codes that require cross-referencing with manufacturer specifications to determine the actual size.
- On packaging or vehicle-era labels: When purchasing, size details are often listed on the rotor packaging, a label, or in the parts catalog rather than on the rotor itself.
Note that the exact location varies by manufacturer and rotor design; if you can’t locate a size stamp on the rotor, check the packaging or consult the vehicle’s service manual or the parts supplier for the correct specification.
Rotor design variations that affect stamping
Some rotor lines emphasize visible stamping on the face for quick reference, while others rely on a central part number that must be looked up in an official catalog. Aftermarket rotors may differ more widely in where the size data appears compared with OEM replacements.
How to read rotor size markings
Once you find the markings, here’s how to interpret them. Sizes are usually expressed as diameter by thickness, and may include additional codes for bolt pattern or compatibility.
- Diameter: A number representing the rotor’s outer diameter, commonly the first figure (for example, 320 implies 320 mm or about 12.6 inches).
- Thickness: A second number, often following an “x” or listed after the diameter, indicating the rotor’s minimum thickness (for example, 28 means 28 mm).
- Bolt pattern and hub details: Some marks include the bolt circle diameter (PCD) and the number of bolts, such as 5x114.3, though this is not universal to rotor size itself.
- Part numbers and manufacturer codes: In many cases, the stamped code is a part number that you cross-reference with the supplier or OEM catalog to derive the exact size and compatibility.
If interpretation isn’t straightforward, consult the rotor’s installation guide or contact the supplier with the stamped code to confirm the correct size.
Examples of size formats you might see
Size formats vary by region and manufacturer. Common formats include metric expressions like “320x28” (320 mm diameter, 28 mm thickness) or imperial expressions such as “12.6 x 1.1 in” (approximately 320 x 28 mm). Some stamps may be minimal, requiring catalog cross-referencing to translate to usable dimensions.
Where to look other than the rotor itself
If the rotor itself doesn’t display a clear size, these other sources can help you verify the correct size for replacement or upgrade.
- Vehicle VIN or owner’s manual: The manufacturer’s specifications list the correct rotor size for both front and rear axles.
- Parts retailer catalogs: Entering your vehicle details in a retailer’s system typically reveals the exact rotor size and compatible options.
- OEM cross-reference guides: OEM rotor part numbers can be cross-checked against official catalogs to confirm size and fitment.
Always double-check with an authoritative source before ordering or installing rotors to ensure proper fit and braking performance.
Practical tips for ordering
To minimize errors, note the vehicle’s year, make, model, and trim, and verify whether you need front or rear rotors, as sizes can differ between axles. When in doubt, compare the stamped codes with an official parts catalog or contact the supplier for confirmation.
Summary
Rotor size is not stamped in a single universal location. Look on the rotor face, hub area, or hat for stamped markings, and don’t overlook packaging or manuals as sources of the size. If markings are unclear, use the part number to look up exact specifications in an official catalog or consult the vehicle manufacturer or retailer to ensure you get the correct rotor size and fitment.
Bottom line: Accurate rotor sizing relies on reading stamped codes or cross-referencing part numbers with official catalogs, and when in doubt, verification with the manufacturer or parts supplier is essential for safety and performance.
