1986-1992 Mazda RX-7 Coil Springs: Decoding AAS, Sag, and Replacement

Understanding 1986-1992 RX-7 (FC) Suspension Variants

Before buying any suspension part for a second-generation (FC) RX-7, you must first identify which suspension system your car has. The coil springs are different between trims, and using the wrong ones will negatively affect ride height, handling, and safety.

• Standard Suspension: This was the base setup on most non-turbo models. It provides a balance of comfort and performance for daily driving.
• Heavy Duty (HD) Suspension: Some models were equipped with a slightly stiffer suspension package for improved handling, which included different springs and shocks.
• Auto Adjusting Suspension (AAS): Found on GXL models, this was an advanced electronic system for its time. It did not use air springs; it used conventional coil springs paired with special electronically adjustable shock absorbers. A microprocessor controlled the firmness of the shocks based on speed, braking, and cornering forces. The springs for AAS cars were specifically matched to these unique shocks.

Symptoms of Failing Coil Springs

Coil springs wear out slowly over time, a condition often called "spring sag." Because it happens gradually, many drivers don't notice the degradation in ride quality. Here are the most common signs that your RX-7's springs are worn or broken:

• Sagging Ride Height: This is the most obvious symptom. The car will sit lower than it should, either at one corner or across an entire axle. It's common for the driver's side to sag more over time due to the weight of the driver. You can measure from the center of the wheel to the top of the fender arch on all four corners to check for inconsistencies.
• Clunking or Rattling Noises: A broken spring coil can move around in its seat, creating a loud clunking or rattling sound, especially when going over bumps or turning.
• Bouncy or Harsh Ride: Worn springs can no longer effectively absorb impacts, leading to a ride that feels excessively bouncy or harsh. The shocks and struts are forced to work harder, which can cause them to wear out prematurely.
• Uneven Tire Wear: Incorrect ride height from a sagging spring throws off the car's alignment geometry, causing tires to wear unevenly on their inner or outer edges.
🎬 See the top signs of a failing spring and repair costs

Buying a Used 1986-1992 RX-7 Coil Spring: A Buyer's Guide

Given the age of the FC RX-7, new OEM springs can be expensive or difficult to find. A good set of used OEM springs can be a cost-effective way to restore your car's original stance and handling. Here’s what to look for.

Step 1: Verify Compatibility

This is the most critical step. You must know if your car is a base model, has the Heavy Duty suspension, or is an AAS-equipped GXL. Springs are not interchangeable between these systems. Furthermore, front and rear springs are different, and sometimes left and right springs have different part numbers. Always buy springs in matching pairs (front set or rear set) to ensure consistent performance and ride height.

Step 2: Physical Inspection

When inspecting a used coil spring, look for the following:

• Cracks: Carefully inspect the entire length of the coil, especially near the top and bottom where it sits in the perch. Run your hand along the coil to feel for sharp breaks or fractures, which may be hidden under the protective coating. A cracked spring is unsafe and must be discarded.
• Heavy Rust or Pitting: Surface rust is common, but deep pitting or flaking rust weakens the metal and can lead to failure. Avoid springs with significant corrosion.
• Modifications: Never buy springs that have been cut or heated. This is a dangerous and improper way to lower a vehicle, as it ruins the spring's integrity and makes the spring rate unpredictable.
• Protective Coating: Check that the original coating is mostly intact. Once this coating is compromised, the spring becomes much more susceptible to rust.

Why Used OEM Can Be Better Than Cheap Aftermarket

Mazda engineered the original springs to provide a specific ride and handling balance. A good-condition used OEM set will restore that factory feel. While high-quality aftermarket performance springs (like those from Racing Beat, Tein, or BC Racing) are excellent for upgrades, cheap, no-name aftermarket springs can be a gamble. They may provide an undesirable ride height, a harsh ride, or have questionable long-term durability.

Known Issues, Recalls, and TSBs

For a vehicle of this age, there are no active recalls specifically for coil springs. Most recalls for the 1986-1992 RX-7 pertain to other issues like fuel systems or seat belts. There are no specific Technical Service Bulletins (TSBs) related to coil spring failure, though some TSBs mention suspension noises that could be related to various components. The primary known issue is age-related spring sag, which is a common maintenance item for these cars.

Replacement Overview & Difficulty

Replacing coil springs is a job for experienced DIY mechanics or a professional shop due to the safety risks involved.

• Difficulty Rating: 4 out of 5
• Key Challenge: The front springs are part of the MacPherson strut assembly and are under extreme compression. A special tool called a spring compressor is required to safely remove and install them. Mishandling a compressed spring can result in serious injury. The rear springs are separate from the shocks and may not require a compressor, but the suspension must still be carefully disassembled.

The basic process involves lifting the vehicle, removing the wheel, disassembling suspension components like control arms and sway bar links to remove the strut assembly (front) or spring (rear), compressing the old spring to remove it, and then carefully installing the new one.

OEM Part Numbers

This list contains known OEM part numbers. It is not exhaustive, and you must verify the correct part for your specific vehicle's VIN and suspension type before ordering.

• FB01-28-011A
• FB01-34-011A
• FB01-34-011B (Front, Right, without AAS, without HD)
• FB01-34-021B
• FB05-28-011A
• FB43-28-011B
• FB43-34-011A
• FB44-34-011
• FB44-34-021
• FB67-28-011A
• FB67-34-011
• FB67-34-021
• FC01-28-011 (Rear)
• FC33-28-011

Frequently Asked Questions (FAQ)