2006-2015 Mazda Miata Rear Upper Control Arm: Solving Clunks & Loose Handling
This guide covers diagnosing, inspecting, and replacing the rearward upper control arms on your NC-generation Mazda MX-5 Miata.
- The NC Miata has two upper control arms per side in the rear; the most common OEM part numbers refer to the rearward arms which are side-specific.
- The primary failure mode is worn rubber bushings, leading to clunking noises, loose handling, and uneven inner tire wear.
- Seized alignment bolts are the biggest installation challenge and may require being cut off, so new bolts should be purchased beforehand.
- A professional four-wheel alignment is not optional—it is mandatory immediately after replacing this part to ensure safety and prevent tire damage.
Identifying the Correct Rear Upper Control Arm
The rear suspension on the 2006-2015 (NC) Miata has two upper arms on each side: a forward arm and a rearward arm. This guide specifically addresses the rearward upper arm. These arms are side-specific, meaning the left and right sides are not interchangeable. Always verify the part number for the side you are replacing.
- Right (Passenger Side) Rearward Upper Arm: NE51-28-600A, NE51-28-600B, NE5128600B
- Left (Driver Side) Rearward Upper Arm: NE51-28-650, NE51-28-650A, NE51-28-650B
These arms are often sold as an assembly that includes the inner and outer rubber bushings already pressed in.
Symptoms of a Failing Rear Upper Control Arm
Failure of the rear upper control arm is almost always due to worn-out rubber bushings. Over time, the rubber cracks, tears, or collapses, creating excess play in the suspension. When this happens, you may notice one or more of the following symptoms:
- Clunking or Knocking Noises: A distinct clunking or thudding sound from the rear of the car, especially when driving over bumps, potholes, or uneven road surfaces. This is the sound of the loose arm moving and making metal-to-metal contact.
- Vague or Unstable Handling: The rear of the car may feel 'loose' or disconnected from your steering inputs. You might feel the car wander slightly or require more steering corrections to keep it straight, particularly at highway speeds.
- Pulling to One Side: A severely worn control arm can cause the vehicle's alignment to shift, making the car pull to the left or right.
- Uneven Tire Wear: A bad control arm allows the wheel alignment (specifically camber and toe) to change dynamically. This often results in accelerated wear on the inner edge of the rear tires.
- Excessive Vibrations: While less common for this specific arm, worn bushings can fail to absorb road vibrations, which may be felt in the seat or cabin.
Pro Tip: A quick visual inspection can often confirm a bad bushing. Look at the rubber ends of the control arm. If you see significant cracking, tearing, or if the rubber appears collapsed and off-center, it's time for a replacement.
Known Issues, TSBs, and Recalls
There are no specific recalls or Technical Service Bulletins (TSBs) from Mazda for the rear upper control arms on the 2006-2015 MX-5 Miata. Failure is typically considered normal wear and tear. The most significant known issue is not with the part itself, but with its removal.
Warning: The bolts used to adjust wheel alignment, which pass through the control arm bushings, are notorious for seizing due to rust. In many cases, especially in regions that use road salt, these bolts become fused to the inner metal sleeve of the bushing. Attempting to remove them can be extremely difficult and may require cutting the bolts out with an angle grinder or reciprocating saw. Always factor in the cost of new alignment bolts when planning this repair.
Buying a Used Rear Upper Control Arm: What to Check
A low-mileage, used OEM control arm can be an excellent value, often providing better longevity than a cheap aftermarket alternative due to the quality of the original Mazda rubber bushings. Here’s what to inspect before buying:
- Inspect the Bushings: This is the most critical check. The rubber should be pliable, not dry or brittle. Look for any cracks, tears, or signs of fluid leakage (from fluid-filled bushings, though these are typically solid rubber). Avoid any arm where the center metal sleeve is significantly off-center, as this indicates a collapsed bushing.
- Check for Bends and Damage: Look down the length of the arm to ensure it is perfectly straight. Any bend, no matter how slight, means the arm was compromised in an accident and should be rejected. Check for deep gouges or cracks in the metal body.
- Examine for Corrosion: Surface rust is normal, but avoid arms with heavy, flaking rust that compromises the structural integrity of the part. An arm from a southern or western climate is always preferable.
- Verify the Part Number: Double-check that you are buying the correct arm for your vehicle's side (Left/Driver vs. Right/Passenger). The part numbers NE51-28-600B (Right) and NE51-28-650B (Left) are not interchangeable.
Cost Comparison for Rear Upper Control Arm Replacement
| Part Type | Estimated Cost (Per Arm) |
|---|---|
| New OEM | $105 - $125 |
| New Aftermarket | $50 - $90 |
| Used OEM | $40 - $75 |
| Shop Labor | $140 - $250 |
Note: Costs are estimates and do not include taxes, shipping, or the mandatory wheel alignment.
Installation Guide & Difficulty
- Difficulty: 3 out of 5
- DIY Feasible: Yes, for experienced mechanics with the right tools.
- Estimated Time: 1.5 - 2.5 hours per side.
Replacing the rear upper control arm is mechanically straightforward but can be made difficult by seized bolts. The basic process involves supporting the vehicle securely, removing the rear wheel, unbolting the arm from the subframe and the wheel knuckle, and installing the new arm.
Warning: Professional Alignment is Mandatory. Replacing this control arm will significantly alter the rear wheel alignment. The car will be unsafe to drive at speed and will suffer from rapid tire wear until a professional four-wheel alignment is performed. Do not skip this step.
Frequently Asked Questions (FAQ)
Do I need to replace the rear upper control arms in pairs?
If one arm has failed due to normal wear and high mileage, the other side is likely in similar condition. In this case, it is best practice to replace them in pairs. However, if an arm was damaged from a specific event like hitting a curb, you only need to replace the damaged side.
What's the difference between the forward and rearward upper arms?
They are different lengths and have different part numbers. Both work together to control the wheel's camber (tilt in or out). You must use the correct arm for the correct position and side.
Can I just replace the bushings instead of the whole arm?
Yes, replacement bushings are available. However, removing the old bushings and pressing in new ones requires a hydraulic shop press. For most DIY mechanics, replacing the entire control arm assembly is faster and easier.
Is an alignment really necessary after replacing a control arm?
Yes, absolutely. The mounting points for this arm directly influence the rear wheels' camber and toe settings. Failure to get a professional alignment will result in poor handling, unsafe driving characteristics, and will destroy your rear tires in a very short time.
Technical Specifications
OEM Part Numbers: NE51-28-600A NE51-28-600B NE5128600B NE51-28-650 NE51-28-650A NE51-28-650B
Side-specific design. Includes pre-installed rubber bushings. Connects rear subframe to wheel knuckle.
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.
- Mazda MX-5 Miata:
- Identifying the Correct Rear Upper Control Arm
- Symptoms of a Failing Rear Upper Control Arm
- Known Issues, TSBs, and Recalls
- Buying a Used Rear Upper Control Arm: What to Check
- Cost Comparison for Rear Upper Control Arm Replacement
- Installation Guide & Difficulty
- Frequently Asked Questions (FAQ)
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