240sx Polyurethane Bushings: Full Suspension Upgrade

The Nissan 240SX, a legend in drifting, time attack, and even spirited street driving, is known for its well-balanced chassis and potential for modification. One of the most impactful upgrades you can make to improve handling and responsiveness is a full suspension bushing replacement, often opting for polyurethane (poly) bushings. This article will delve into the pros and cons of poly bushings, the installation process, and what to expect from this upgrade on your 240SX. We're assuming you've got some wrenching experience and are comfortable with basic suspension work.

Understanding Bushings: The Foundation of Suspension

Before diving into polyurethane, let's understand what bushings actually do. Bushings are compliant interfaces, typically made of rubber, that connect suspension components to the chassis or other suspension parts. Think of them as the silent heroes of your suspension system. Their primary function is to:

Isolate Noise and Vibration: Rubber bushings absorb vibrations from the road, preventing them from transmitting directly into the cabin.
Allow Controlled Movement: Bushings allow for the necessary articulation of suspension components as the wheels move up and down.
Maintain Suspension Geometry: By controlling the range of motion, bushings help maintain the desired alignment angles (camber, caster, toe) as the suspension cycles.

However, stock rubber bushings have limitations. Over time, they degrade, crack, and lose their stiffness. This leads to sloppy handling, imprecise steering, and increased suspension noise. Worn bushings allow for unwanted movement, negatively affecting alignment and overall vehicle control.

Polyurethane Bushings: The Performance Alternative

Polyurethane is a synthetic polymer that offers a stiffer and more durable alternative to rubber. When used in suspension bushings, poly offers several key advantages:

Increased Stiffness: Poly bushings deflect less under load than rubber, resulting in a more responsive and direct feel. This translates to sharper turn-in, reduced body roll, and improved handling precision.
Improved Durability: Polyurethane is far more resistant to wear, tear, and degradation from oil, chemicals, and environmental factors compared to rubber. This means they will last significantly longer, especially in harsh driving conditions.
Greater Control: The reduced deflection of poly bushings helps maintain proper suspension geometry under hard cornering and braking, leading to more predictable handling characteristics.

However, there are also some drawbacks to consider:

Increased Noise, Vibration, and Harshness (NVH): Poly bushings transmit more road vibrations and impacts into the cabin compared to rubber. This can result in a harsher ride, especially on rough roads.
Potential for Squeaking: Polyurethane can squeak if not properly lubricated. Regular lubrication is essential to prevent noise and ensure smooth operation.
Installation Complexity: Some poly bushings can be more challenging to install than rubber bushings, often requiring specialized tools or techniques.
Ride Comfort: The stiffer ride might be undesirable for a daily driver focused on comfort.

Choosing the Right Poly Bushings for Your 240SX

When selecting poly bushings for your 240SX, consider your intended use and driving style. Different durometers (hardness) of polyurethane are available. Durometer is measured on a Shore A scale. Lower numbers indicate softer bushings, while higher numbers indicate harder bushings. For example:

Softer Poly (70-80A): Offers a good balance between performance and comfort. Suitable for street cars that see occasional track use.
Medium Poly (80-90A): Provides a noticeable increase in performance but may result in a harsher ride. Ideal for cars that are primarily driven on the street but see frequent track days.
Hard Poly (90A+): Offers maximum performance and minimal deflection. Best suited for dedicated track cars or drift cars where ride comfort is not a primary concern.

Pay close attention to the location of the bushing. Some areas, like the rear subframe, benefit from stiffer bushings, while others, like the front lower control arm, might be better suited for a slightly softer compound to avoid excessive NVH.

Essential Tools and Materials

Before you start, gather the necessary tools and materials:

* Jack and Jack Stands: Essential for safely lifting and supporting the vehicle. * Wheel Chocks: To prevent the car from rolling. * Socket Set and Wrenches: Metric sizes, including a breaker bar for stubborn bolts. * Ball Joint Separator (Pickle Fork or Press-Type): For separating ball joints if you're replacing control arm bushings. * Hammer: For persuading stubborn components. * Punch and Drift Set: For removing old bushings. * Bushing Press or Shop Press: Absolutely crucial for installing new bushings without damaging them. A C-clamp kit can work in some instances but isn't ideal. * Penetrating Oil: To loosen corroded bolts and bushings. PB Blaster or similar is highly recommended. * Grease Gun: For lubricating bushings, especially those with grease fittings. * Lithium or Silicone-Based Grease: Specifically designed for polyurethane bushings. Avoid petroleum-based greases, as they can degrade polyurethane over time. * Safety Glasses and Gloves: Protect your eyes and hands. * Torque Wrench: To tighten bolts to the correct specifications. Refer to your service manual. * Service Manual: Provides valuable information on torque specs, procedures, and diagrams. * Alignment After Installation: A professional wheel alignment is mandatory after any suspension work.

Step-by-Step Installation Guide (General Overview)

This is a general overview; specific instructions will vary depending on the location of the bushing and the kit you purchased. Always refer to the manufacturer's instructions for your specific kit.

Preparation: Safely lift and support the vehicle on jack stands. Remove the wheels.
Disassembly: Loosen and remove the nuts and bolts securing the suspension component you're working on. Use penetrating oil to help loosen corroded fasteners. Take pictures before disassembly to ensure you remember how everything goes back together.
Bushing Removal: This is often the most challenging part. There are several methods:
- Pressing: Use a bushing press or shop press with appropriate adapters to press the old bushing out. This is the preferred method.
- Burning: As a last resort, you can carefully burn out the old rubber bushing using a torch. Be extremely cautious and avoid damaging the surrounding metal. Allow the component to cool completely before proceeding. This method is generally NOT recommended due to safety and potential damage.
- Cutting/Drilling: Carefully cut or drill out the old bushing. Be careful not to damage the surrounding metal.
Cleaning: Thoroughly clean the bushing bore (the hole where the bushing sits) with a wire brush or sandpaper. Remove any rust, dirt, or debris.
Bushing Installation: Apply a generous amount of polyurethane-compatible grease to the new bushing and the bushing bore. Press the new bushing into place using a bushing press or shop press. Ensure the bushing is properly seated and aligned. Some bushings are multi-piece and require proper orientation.
Reassembly: Reinstall the suspension component, tightening the nuts and bolts to the manufacturer's specified torque.
Repeat: Repeat the process for all remaining bushings.
Final Check: Double-check all nuts and bolts to ensure they are properly tightened. Reinstall the wheels and lower the vehicle to the ground.
Alignment: Get a professional wheel alignment immediately after installation. This is crucial for proper handling and tire wear.

Tips and Tricks

* Freezing the Bushings: Freezing the poly bushings for a few hours before installation can shrink them slightly, making them easier to press in. * Heating the Component: Heating the surrounding metal (carefully!) with a heat gun can expand it slightly, also making bushing installation easier. * Proper Lubrication is Key: Don't skimp on the grease! Use a high-quality polyurethane-compatible grease. Re-grease the bushings periodically, especially if you notice any squeaking. * Don't Overtighten: Overtightening bolts can damage the bushings or the suspension components. Use a torque wrench and follow the manufacturer's specifications. * Work Methodically: Tackle one component at a time to avoid confusion. Take pictures and label parts as you disassemble. * Be Patient: Bushing replacement can be time-consuming, especially if you encounter stubborn bolts or bushings. Don't rush the process; take your time and do it right. * Subframe Bushings: These can be particularly challenging, often requiring dropping the entire subframe. Consider the complexity before attempting this at home.

Expected Results and Considerations

After installing poly bushings, you can expect a noticeable improvement in handling and responsiveness. Steering will feel sharper, body roll will be reduced, and the car will feel more planted and predictable, especially during cornering. However, you will also experience an increase in NVH. The ride may feel harsher, and you may hear more road noise and vibrations. Be prepared to lubricate the bushings regularly to prevent squeaking.

A full poly bushing upgrade can significantly enhance the performance of your 240SX. However, it's important to weigh the pros and cons carefully and choose the right durometer and bushing locations for your specific needs and driving style. With proper installation and maintenance, poly bushings can provide years of improved handling and performance. Remember to always prioritize safety and consult a professional if you're unsure about any aspect of the installation process. Good luck and happy wrenching!