2014-2021 BMW i3 Rear Cross-Member (39206868859): More Than a Skid Plate, Fits Both BEV & REx
This guide clarifies the function of the i3's rear structural cross-member, confirms it fits all models, and details the separate plastic underbody panels you might be looking for.
- The part number 39206868859 is a structural rear cross-member, not a skid plate, and it fits ALL 2014-2021 i3 models (BEV and REx).
- The plastic underbody panels (splash shields) ARE different between BEV and REx models; verify compatibility before buying.
- A critical recall (17V088000) for 2014-2017 REx models involves a fire risk from a chafing fuel line in the underbody area. Ensure this has been fixed.
- Replacement is very easy for a DIYer, requiring only basic tools and access to the underside of the vehicle.
Part Terminology: Cross-Member vs. Skid Plate
It is important to understand the difference between two types of parts on the underbody of the 2014-2021 BMW i3. Many drivers use the term 'skid plate' to refer to any protective panel underneath the car.
- Rear Cross-Member (OEM Part #39206868859): This is a structural metal bar located at the rear of the vehicle. Its main job is to add strength and rigidity to the car's frame, not to act as a shield.
- Underbody Panels / Splash Shields: These are the plastic or composite panels found at the front and along the bottom of the car. Their purpose is to improve airflow and protect components from water and small road debris. These are the parts most likely to be damaged from scraping on curbs or road hazards.
Compatibility Warning: While the rear cross-member (39206868859) fits all versions of the i3 (BEV, REx, i3s), the plastic underbody panels can differ between the all-electric (BEV) and Range Extender (REx) models. The REx model has a small gasoline engine and exhaust system that require different panel shapes. Always verify the specific part number for your vehicle's VIN when replacing plastic splash shields.
Symptoms of Failure
Failure symptoms depend entirely on which part is damaged.
Damaged Rear Cross-Member (39206868859)
Because this is a structural part, damage usually results from a significant impact, such as hitting a large object or a severe pothole. Symptoms include:
- Knocking or Clunking Noises: A bent or broken cross-member can cause noise from the rear of the car, especially over bumps.
- Poor Wheel Alignment: Damage to this part can affect rear suspension geometry, leading to alignment issues or unusual tire wear.
- Visible Damage: The part may be visibly bent, cracked, or broken upon inspection.
Damaged Plastic Underbody Panels
These panels are far more commonly damaged. Symptoms are usually obvious and not subtle.
- Scraping or Dragging Noises: The most common symptom is a panel hanging loose and dragging on the pavement.
- Rattling or Flapping Sounds: At higher speeds, a loose panel can flap in the wind, creating noise.
- Visible Damage: You may see the panel hanging down, or find it cracked, torn, or missing sections.
Buying a Used 2014-2021 BMW i3 Underbody Part
Purchasing a used OEM part is often a smart choice, as the original BMW components are designed for a precise fit and durability. Aftermarket structural parts for the i3 are generally not available, and aftermarket plastic shields can be brittle and fit poorly.
What to Inspect on a Used Rear Cross-Member (39206868859)
- Check for Straightness: Lay the part on a flat surface. It should not have any visible bends, twists, or warping. A bent cross-member is structurally compromised and should not be used.
- Inspect Mounting Points: Check all bolt holes for cracks, elongation, or severe corrosion. These areas are critical for a secure installation.
- Look for Cracks: Carefully inspect the entire part, especially around any welds, for signs of cracking from stress or impact.
What to Inspect on a Used Plastic Underbody Panel
- Check for Cracks and Tears: Minor surface scratches are normal, but avoid any parts with large cracks or tears that compromise their integrity.
- Verify All Mounting Tabs: Ensure all the plastic tabs and mounting holes around the perimeter of the panel are intact. Broken tabs are a primary reason these panels come loose.
- Confirm Part Number: Double-check that the OEM part number on the panel matches the one required for your specific i3 model (BEV or REx).
Known Issues, Recalls, and Technical Service Bulletins (TSBs)
While there are no recalls specifically for the underbody panels or cross-member, a critical recall affects the Range Extender (REx) model in this area.
NHTSA Campaign ID 17V088000: Fuel Vent Line Chafing (REx Models Only)
On 2014-2017 BMW i3 REx models, the fuel tank vent line can rub against the protective sleeve of a battery cable. This can wear a hole in the line, causing a fuel vapor leak that increases the risk of fire. The remedy involves dealers inspecting the line, replacing it if necessary, and installing a clip to prevent future contact. Before purchasing a used i3 REx, or if you own one, ensure this recall has been performed.
No other major TSBs or recalls directly relate to the underbody shields or structural components.
Cost Comparison
Prices can vary based on condition and supplier. The following is an estimated range for the rear cross-member (39206868859) and associated labor.
| Part/Service | Estimated Cost | Notes |
|---|---|---|
| New OEM Cross-Member | $280 - $350 | Genuine BMW part from a dealer or online retailer. |
| New Aftermarket Cross-Member | Not Available | Aftermarket structural components for this model are not common. |
| Used OEM Cross-Member | $40 - $75 | A significant savings for a durable structural part. |
| Shop Labor to Replace | $75 - $150 | Estimated 0.5-1.0 hours of labor. It is a straightforward bolt-off, bolt-on job. |
Replacement Guide (1/5 Difficulty)
Replacing the rear cross-member or the plastic underbody panels is a simple job suitable for a DIY mechanic with basic tools. The process generally involves removing several 8mm bolts.
Pro Tip: When replacing any underbody panel, it's a good idea to purchase a new set of fasteners. Old bolts can be corroded, and plastic clips often become brittle and break upon removal.
- Raise the Vehicle: Safely raise the rear of the vehicle using a jack and support it with jack stands. Ramps can also be used.
- Locate the Part: Identify the damaged cross-member or panel that needs to be replaced.
- Remove Fasteners: Using an 8mm socket or wrench, remove all bolts securing the part to the vehicle's chassis and any adjoining panels. Keep track of different bolt lengths or types if they exist.
- Remove the Part: Carefully lower the old part from the vehicle.
- Install the New Part: Position the new part and loosely thread in all bolts by hand to ensure proper alignment.
- Tighten Fasteners: Once aligned, tighten all bolts securely. Do not overtighten, as this can damage the plastic panels or threads.
- Lower the Vehicle: Safely lower the vehicle back to the ground.
Frequently Asked Questions (FAQ)
Is the rear cross-member (39206868859) different for the i3 BEV and REx models?
No. The structural rear cross-member is the same for all 2014-2021 i3 models, including the all-electric (BEV), Range Extender (REx), and the sporty 's' variants.
Can I drive with a broken or missing plastic underbody panel?
While you can drive the vehicle, it is not recommended for long. A missing panel can negatively affect aerodynamics, potentially reducing range, and exposes sensitive components to water, salt, and debris. A panel that is dragging is a safety hazard and should be removed or secured immediately.
Why is a used OEM panel often better than a new aftermarket one?
Used OEM panels are made from the original high-quality, flexible materials BMW designed for the car, ensuring a perfect fit. Many new aftermarket plastic parts are made from cheaper, more brittle plastic that can crack easily and may not align perfectly with factory mounting points.
What is the most important issue to check on a used i3 REx?
The most critical safety check is for NHTSA recall 17V088000. This involves a potential fuel vapor leak from a chafed vent line in the rear underbody area. You can check if this recall work has been completed by entering the car's VIN on the NHTSA website or contacting a BMW dealer.
Technical Specifications
OEM Part Numbers: 39206868859 39-20-6-868-859
Material: Steel or high-strength aluminum alloy. Position: Rear.
We Have This Part in Stock
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.
- BMW i3:
- 🛍️ Shop This Part
- Part Terminology: Cross-Member vs. Skid Plate
- Symptoms of Failure
- Damaged Rear Cross-Member (39206868859)
- Damaged Plastic Underbody Panels
- Buying a Used 2014-2021 BMW i3 Underbody Part
- What to Inspect on a Used Rear Cross-Member (39206868859)
- What to Inspect on a Used Plastic Underbody Panel
- Known Issues, Recalls, and Technical Service Bulletins (TSBs)
- Cost Comparison
- Replacement Guide (1/5 Difficulty)
- Frequently Asked Questions (FAQ)
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