Using 303 Spray on Suspension Parts: What You Need to Know

Many car owners wonder if 303 Aerospace Protectant can be used on suspension components. The answer is yes, but only on specific parts and with careful technique. 303 spray is a water-based protectant designed for rubber, plastic, and vinyl. When applied correctly, it helps preserve rubber bushings, dust boots, and bump stops by blocking UV rays and preventing dry rot. However, it is not a lubricant and should never be used on friction surfaces like brake rotors or shock absorber shafts. This guide explains where to apply 303 spray, how to do it properly, and what to avoid.

What Is 303 Aerospace Protectant?

303 Aerospace Protectant is a well-known cleaner, conditioner, and UV protectant for non-porous surfaces such as rubber, plastic, and vinyl. Unlike many silicone-based dressings, 303 is water-based and contains no petroleum solvents, making it safe for rubber without causing swelling or cracking over time. It leaves a dry, matte finish that does not attract dust or grease. Originally developed for aerospace applications, it is now widely used on automotive surfaces like dashboards, trim, and tires. On suspension parts, its main benefits are UV protection, restoring flexibility, and prolonging the life of rubber components.

Where to Apply 303 Spray on Suspension

Rubber Bushings

Rubber bushings in control arms, sway bars, and trailing arms are prime candidates for 303 spray. Exposure to UV rays, heat, and road salt can cause them to harden and crack. Regular application of 303 helps keep the rubber supple and reduces the risk of premature failure. Only apply to the exposed rubber portion; avoid getting the spray on metal sleeve surfaces or contact points that rely on friction. Clean the bushing area thoroughly before application to ensure the product bonds properly.

Dust Boots and Bump Stops

Dust boots protect tie rod ends, ball joints, and shock shafts from dirt and moisture. Bump stops are rubber pieces that cushion suspension at full compression. Both benefit from 303 spray because they remain flexible and resist ozone cracking. When applying, use a light mist on a cloth or a small foam applicator. Do not spray directly onto the boot or stop to prevent overspray onto nearby metal or friction surfaces. For shock dust boots, be especially careful not to get any product on the shock shaft, as this can degrade the seal and cause oil leaks.

Parts to Avoid

• Coil Springs: 303 has no benefit on metal springs—it is not a lubricant or rust preventative. Use a dedicated coating if needed.
• Shock Absorbers and Struts: The seal and shaft are designed to work dry. Applying 303 to the shaft can attract dirt and cause premature wear.
• Brake Components: Never spray 303 on brake calipers, rotors, pads, or lines. It can reduce braking effectiveness and create a fire hazard.
• Polyurethane Bushings: Some polyurethane formulations may react poorly with 303. Test on a small hidden area first or consult the bushing manufacturer before applying.

How to Apply 303 Spray on Suspension Parts

Preparation

Clean the rubber parts with a mild soap and water solution to remove dirt, grease, and old protectants. Rinse and let dry completely. Use masking tape or paper to cover nearby areas you want to protect from overspray, such as brake rotors, exhaust components, and painted surfaces.

Application Technique

Shake the 303 spray bottle well. Instead of spraying directly onto the suspension part, spray the product onto a clean microfiber cloth or a foam applicator pad. Wipe the cloth or pad onto the rubber, covering it evenly. For hard-to-reach areas, you can spray a small amount onto the part, but immediately spread it with a cloth to avoid puddling. Allow the product to sit for 2–3 minutes, then buff off any excess with a dry cloth. Leaving a wet film will attract dust and may leave streaks.

Frequency

Apply 303 spray every 3 to 6 months, depending on your driving conditions. Vehicles driven daily in sunny climates or exposed to road salt should be treated more often. Garage queens or low-mileage cars can get away with once a year. Reapply sooner if the rubber starts to look dry or feel stiff.

Benefits of Using 303 Spray on Suspension

• UV Protection: Blocks harmful ultraviolet rays that accelerate rubber aging.
• Flexibility: Keeps rubber soft and pliable, reducing the likelihood of cracking.
• Cleans: Helps remove light dirt and restores a clean, matte appearance.
• Non-Greasy: Unlike silicone sprays, 303 does not leave a wet residue that attracts dirt.
• Safe: Water-based formula does not damage paint, metal, or adjacent components when used correctly.

Potential Risks and Limitations

• Not a Lubricant: 303 should never be used on ball joints, tie rods, or other moving metal parts that require grease. It will not reduce friction and can wash away grease over time.
• Compatibility: While safe for most original equipment rubber, aftermarket or high-performance polyurethane bushings may be sensitive. Always spot-test first.
• Overspray Dangers: Accidentally spraying 303 onto brake rotors, pads, or shock shafts can cause safety issues. Always mask and use controlled application methods.
• Temporary: 303 is not a permanent fix. Worn or damaged rubber parts must be replaced; this product only slows down aging on healthy rubber.
• Dirt Attraction: If left to pool, the product can appear sticky and attract road grime. Buffing is essential.

Final Recommendation

For stock suspension systems, 303 spray is a reliable way to protect rubber bushings, dust boots, and bump stops. It offers genuine UV protection, keeps rubber flexible, and has a clean finish that does not attract dirt. Always clean the parts before applying, use a cloth or applicator instead of spraying directly, and reapply in line with your exposure. Avoid using it on friction surfaces, lubricated joints, or polyurethane bushings without verification. If your rubber components are already cracked or deteriorated, replace them first; 303 cannot restore lost integrity. When used appropriately, 303 Aerospace Protectant helps extend the life of your suspension rubber without the mess of silicone-based products.