2014-2019 BMW i8 Rear Bumper: A Guide to Covers, Brackets, and Sensor Compatibility

Understanding i8 Rear Bumper Part Numbers

When searching for a rear bumper for the BMW i8, it's easy to encounter confusing part numbers. The main, visible, painted component is the Bumper Cover (also called a bumper skin or fascia). However, other small brackets and supports are also part of the complete assembly.

• Rear Bumper Cover: The primary exterior panel. A common part number for this is 51127394634. This is the part you need if your bumper has cosmetic damage like cracks or deep scratches.
• Center Support Bracket: Part number 51127336296 (which replaces the older 51124824796) is a smaller, structural piece known as a 'Guide Center Rear' or 'Center Support'. This is a mounting component that sits behind the main cover and is typically only replaced if there is deeper structural damage.

This guide focuses primarily on the main Rear Bumper Cover, as it is the most commonly damaged and replaced part.

Symptoms of Failure

Failure of the rear bumper assembly can manifest in physical damage or electronic issues.

Physical Damage

The most common issue is visible damage from an impact. This can range from minor scuffs and scratches to severe cracks, punctures, or deformation. Because the i8 is so low to the ground, scraping on steep driveways is also a common cause of damage to the lower edges. A severely damaged bumper can become loose, flap at speed, or have poor alignment with surrounding body panels.

Park Distance Control (PDC) Malfunction

If your i8's parking system acts up, the bumper assembly is a likely culprit. Symptoms include:

• A loud, continuous beep as soon as you shift into reverse.
• A 'PDC Malfunction' message appearing on the iDrive screen.
• Sensors that do not detect obstacles at all.
• 'Phantom' beeping, where the system reacts to rain, dirt, or nothing at all.

Often, these issues are caused by a single failed ultrasonic sensor mounted in the bumper. Water intrusion or wiring damage within the bumper harness can also cause these symptoms.

Buying a Used Rear Bumper Cover

For a specialty vehicle like the i8, a used Original Equipment Manufacturer (OEM) bumper cover is almost always a better choice than a new aftermarket one. Aftermarket panels for low-volume, high-precision cars often suffer from poor fitment, which will be very noticeable against the i8's tight body gaps. Here’s what to inspect before buying a used OEM cover.

1. Check All Mounting Tabs and Points

This is the most critical inspection. Carefully examine every single mounting tab, clip slot, and screw hole around the perimeter of the bumper, especially on the top edge and where it meets the quarter panels. A used bumper with even one broken tab can be impossible to align correctly, leading to unsightly gaps or rattles. If a seller's photos are unclear, ask for detailed pictures of all mounting areas.

2. Inspect for Previous Repairs

Look at the backside of the bumper cover. Check for signs of plastic welding, excess glue, or body filler (often visible as sanded, chalky areas). A professionally repaired bumper can be acceptable, but a poor repair will often crack or fail again. Be wary of any bumper with significant previous damage, as its structural integrity may be compromised.

3. Verify Sensor Compatibility

Nearly all i8s were equipped with Park Distance Control (PDC). Ensure the bumper you are buying has the correct number and placement of holes for these sensors. While you can transfer your old sensors to the new bumper, it's a bonus if the used part includes a working set. However, always assume you will need to have the bumper painted to match your car, as even a bumper of the same color may not be a perfect match due to fading and production variations.

Known Issues, Recalls, and Technical Service Bulletins (TSBs)

While there are no recalls specifically for the rear bumper assembly, several recalls and TSBs concern components located in the rear of the vehicle.

• NHTSA Recall 14V-674: Affecting some 2014 models, this recall addresses a potential fuel leak from an improperly welded bolt on the fuel tank. This repair is performed in the rear of the vehicle.
• NHTSA Recall 19V-600: On certain 2019 models, a faulty Electric Motor Electronics (EME) module could shut down high-voltage power, leading to a loss of propulsion.
• NHTSA Recall 15V-882: A small number of 2015 models were recalled for a faulty Dynamic Stability Control (DSC) hydraulic unit that could impair braking and stability.
• TSB B330219: Addresses inconsistent steering or drivability behavior related to the rear axle stiffening plate.

These issues are not caused by the bumper, but a technician working in this area for a bumper replacement may be in a good position to inspect for signs of these related concerns.

Cost Comparison

Replacing a BMW i8 rear bumper can be expensive. A used OEM part offers significant savings over a new dealer part.

Installation Overview

Replacing the rear bumper cover on a BMW i8 is a complex job not recommended for beginners.

• Difficulty: 4 out of 5
• Process: The procedure involves jacking up the car, removing the rear wheels, and taking out the fender liners to access hidden fasteners. The taillights and various trim pieces must also be carefully removed before the bumper cover itself can be unclipped and pulled away. Disconnecting the PDC sensor harness without damaging it is also a critical step.
• DIY Feasibility: Only recommended for experienced DIY mechanics with the proper tools and patience. For most owners, professional installation is the best option to ensure perfect fitment and prevent damage to the complex bodywork.

Frequently Asked Questions (FAQ)

Technical Specifications & Part Numbers