2018-2020 Genesis G80 Front Brake Rotors: Decoding the 345mm vs. 360mm Systems
This guide covers the critical differences between the two available front brake rotor sizes for the 2018-2020 Genesis G80, common failure symptoms, and how to inspect a used part.
- You must verify whether your G80 requires 13.6-inch (345mm) or 14.2-inch (360mm) front rotors before buying; they are not interchangeable.
- The most common failure symptom is a vibration or pulsation felt in the steering wheel when braking, which indicates warped rotors.
- A major safety recall (NHTSA 21V160000) exists for the ABS module, which can short circuit and cause a fire. Ensure this recall has been performed on any vehicle.
- When buying used rotors, you must measure the thickness with a micrometer to ensure it's above the minimum specification and inspect for cracks or heat damage.
Variant Differences: 345mm vs. 360mm Rotors
The most important factor when buying front brake rotors for a 2018-2020 Genesis G80 is identifying the correct diameter. These vehicles were equipped with two different front brake systems, and the parts are not interchangeable.
Warning: Installing the wrong size rotor will result in the brake caliper not fitting or the brake pads not making proper contact. Always verify your vehicle's required rotor size before purchasing.
| Rotor Diameter | Common Applications | Known OEM Part Numbers |
|---|---|---|
| 13.6 inches (345mm) | Standard on 3.8L V6 models. | 51712-3N600, 51712-B1700 |
| 14.2 inches (360mm) | Standard on 3.3T Sport and 5.0L V8 models. | 51712-B1800, 51712-3N800 |
The easiest way to confirm your size is to measure the diameter of the existing rotor. You can do this by removing a wheel and measuring from edge to edge across the face of the rotor. Some aftermarket parts listings may also help you identify the correct size based on your specific trim and engine.
Symptoms of Failing Front Brake Rotors
Worn or damaged brake rotors will produce noticeable symptoms. Ignoring them can lead to reduced stopping power and more expensive repairs.
- Vibration or Pulsation: The most common symptom is a shaking or pulsating feeling in the steering wheel or brake pedal when you apply the brakes, especially from higher speeds. This is typically caused by warped rotors, also known as excessive runout or disc thickness variation (DTV).
- Grinding or Scraping Noises: A loud, metallic grinding sound during braking means the brake pads have likely worn down completely, and the metal backing plate is now grinding against the rotor. This will quickly destroy the rotor and requires immediate attention.
- Squealing or Squeaking: While often a sign of worn brake pads, persistent squealing can also be caused by a glazed or grooved rotor surface.
- Visible Grooves or Hot Spots: A visual inspection may reveal deep circular grooves, scoring, or bluish-colored hot spots on the rotor's surface. These indicate uneven wear or overheating and mean the rotor should be replaced.
Known Issues, TSBs, and Recalls
While there are no recalls specifically for the brake rotors themselves, there is a significant safety recall involving the Anti-Lock Brake System (ABS) that owners should be aware of.
- NHTSA Recall 21V160000: This recall affects 2017-2020 Genesis G80 models. The ABS module can malfunction and cause an electrical short, which may lead to an engine compartment fire, either while driving or parked. The remedy involves dealers replacing the ABS module fuse. Owners were advised to park their vehicles outside and away from structures until the repair was completed.
- Brake Judder/Vibration TSB: While not specific to the G80, Hyundai/Genesis has issued general Technical Service Bulletins (TSBs) like 21-BR-002HG regarding brake service best practices to address issues like brake vibration. The TSB recommends measuring rotor thickness and runout, using on-car brake lathes for resurfacing, and following a specific burnishing (bed-in) procedure after installing new or machined rotors.
Pro Tip: A significant vibration felt during braking at highway speeds can sometimes be caused by corrosion on the rotors, especially if the vehicle has been stored outdoors for an extended period. In some cases, normal driving for a few days may clean the rotor surface and resolve the issue.
Buying a Used 2018-2020 G80 Front Brake Rotor
A used OEM brake rotor can be a cost-effective alternative to a new part, offering the same fit and material quality as the original. However, careful inspection is crucial as it is a wear item.
- Verify the Diameter: First and foremost, confirm you are buying the correct 13.6" (345mm) or 14.2" (360mm) rotor for your G80 model. Bring a tape measure.
- Measure the Thickness: Use a brake rotor micrometer to measure the thickness of the rotor's friction surface. The minimum allowable thickness is typically stamped on the rotor hat or hub. If the rotor is at or below this minimum spec, it cannot be safely used or resurfaced and should be rejected.
- Check for Surface Damage: Inspect the friction surfaces on both sides. Reject any rotor with deep grooves, cracks, or significant rust pitting. A bluish or discolored appearance indicates the rotor has been overheated, which can change the metal's properties and lead to warping.
- Look for Warping (Runout): While hard to check without mounting it, look for uneven wear patterns. Lay the rotor on a flat surface to see if it sits perfectly flat. Any visible wobble is a red flag for warping.
- Why Used OEM? Used OEM rotors often have superior metallurgy and heat dissipation characteristics compared to the cheapest aftermarket options, making them less prone to warping and noise if they are still in good condition.
Replacement Overview
Replacing front brake rotors is a common task for DIY mechanics with the right tools. Always replace rotors in pairs (both front wheels) and install new brake pads at the same time for even braking and optimal performance.
- Difficulty: 2.5 out of 5
- Tools Required: Jack and jack stands, lug wrench, socket set (17mm for caliper bolts), C-clamp or piston compressor, brake cleaner, torque wrench.
- General Steps:
- Safely raise and support the front of the vehicle and remove the wheel.
- Unbolt the brake caliper from its mounting bracket and hang it securely from the suspension with a hook or zip tie. Do not let it hang by the brake hose.
- Remove the caliper mounting bracket.
- Remove the small Phillips head rotor retaining screws, if present. These can be stubborn and may need an impact driver or to be drilled out.
- Pull the old rotor off the hub. If it's stuck, a few firm hits with a rubber mallet on the back side can help loosen it.
- Clean the wheel hub surface of any rust or debris before installing the new rotor.
- Reassemble in reverse order, making sure to clean and lubricate the caliper slide pins.
- Use a torque wrench to tighten the caliper bracket bolts and lug nuts to the manufacturer's specification.
Cost Comparison (Per Pair of Front Rotors)
| Part Type | Estimated Cost | Notes |
|---|---|---|
| New OEM | $280 - $450 | Price varies by rotor size. |
| New Aftermarket | $130 - $350 | Wide range of quality and price. |
| Used OEM | $70 - $150 | Dependent on condition and mileage. |
| Shop Labor | $150 - $250 | For replacing both front rotors and pads. |
Frequently Asked Questions
How do I know for sure if I need 345mm or 360mm rotors?
The most reliable method is to remove a front wheel and physically measure the diameter of the rotor. Alternatively, a Genesis dealer can determine the correct part using your vehicle's VIN. Generally, 3.8L models use 345mm rotors, while the 3.3T Sport and 5.0L V8 models use the larger 360mm rotors.
Do I have to replace my brake pads when I replace my rotors?
Yes, it is highly recommended. Installing old, worn pads on new rotors will create an uneven wear pattern on the new rotors, reducing their lifespan and performance. Most rotor replacement services include new pads.
Can I just resurface my old rotors instead of replacing them?
Sometimes. Rotors can be resurfaced (machined) if they have minor warping or light grooving, but only if they will remain thicker than the minimum thickness specification after machining. If they are already too thin, cracked, or heavily grooved, they must be replaced.
What is "bedding in" new brakes and is it necessary?
Bedding-in, or burnishing, is the process of transferring a thin, even layer of friction material from the new brake pads onto the new rotors. This is crucial for smooth, quiet, and powerful braking. The process typically involves a series of moderate-to-firm stops from a medium speed (e.g., 10 stops from 50 mph down to 10 mph) without coming to a complete stop, followed by a cool-down period.
Technical Specifications
OEM Part Numbers: 51712-3N600 (345mm) 51712-B1700 (345mm) 51712-B1800 (360mm) 51712-3N800 (360mm) 51712B1800 517123N600
Rotor Diameters: 13.6 in (345 mm) or 14.2 in (360 mm). Bolt Pattern: 5-lug.
The information in this article is provided for general reference and educational purposes only. Vehicle specifications, procedures, and part compatibility can vary by production date, trim level, and region. Always consult your vehicle's factory service manual and verify part numbers before purchasing or performing repairs. Safety-critical components such as airbags, seat belts, and braking systems should be installed by a qualified professional.
- Genesis G80: