Heavy Duty Trailer Air Spring - W01-358-9978 S28929 1R12-668

• 4.5–5.00mm Thick Rubber: Manufactured with a heavy-duty, extra-thick rubber compound that exceeds OEM specs to resist dry rotting, ozone cracking, and punctures from highway debris.
• 4140-Grade Steel Studs: Engineered with high-tensile 4140-grade steel mounting studs that are 25% stronger than standard industry hardware, heavily reducing the risk of sheer failures.
• Reinforced Composite Piston: Features a highly durable composite piston (8.05" width) designed to withstand the brutal impacts and intense vertical load stresses of heavy commercial trailers.
• 100% Leak Tested: Subjected to the industry's highest leak test ratio standards after final assembly to guarantee a perfect, airtight seal right out of the box.

Restore your commercial suspension's load-carrying capacity with this premium Heavy Duty Trailer Air Spring by FleetPro Parts & Tires. Engineered as a direct aftermarket replacement rolling lobe/reversible sleeve air spring, this unit provides superior load support, vibration dampening, and long service life. Whether you are hauling heavy freight across the Midwest or navigating rough construction sites, this air spring ensures your trailer remains level, protecting both your cargo and your chassis. We stock these heavily right here in our Hanover Park, Illinois warehouse to ensure lightning-fast shipping for fleets and owner-operators nationwide.

Commercial Load Support: The Heavy Duty Trailer Air Spring Advantage

This Heavy Duty Trailer Air Spring is overbuilt to survive the demanding environments of long-haul trucking. It features a premium 4.5–5.00 mm thick rubber construction that exceeds standard OEM requirements, heavily resisting dry rot, ozone cracking, and road debris. Furthermore, it is equipped with 4140-grade steel studs that are 25% stronger than standard hardware, preventing sheer failures under extreme articulation. Paired with a reinforced composite piston and an industry-leading leak test ratio, this aftermarket air spring delivers reliable, airtight performance shift after shift.

As we continue to grow the largest inventory of commercial truck parts in Illinois, we prioritize suspension hardware that balances industrial strength with cost-effective reliability. Serving as a direct exact-fit replacement for massive industry part numbers including Firestone W01-358-9978, Hendrickson S28929, and Goodyear 1R12-668, this unit is ready to bolt right on and save you from dealership markups. Important Fitment Note: Buying an air spring by make and model alone is not recommended. Always verify your replacement by crossing your original part number or measuring your top/bottom plate mounting configurations prior to purchase.

Vehicle Fitment & Compatibility

This premium aftermarket trailer air spring features a universal design intended for the following commercial applications:

• Make: Universal Trailer Fit (Hendrickson, Freightliner, Volvo, Mack, Alliance, etc.)
• Application: Trailer Air Suspension Systems
• Suspension Type: Rolling Lobe / Reversible Sleeve

Direct Replacement & Cross-Reference Numbers:

This air spring serves as a direct exact-fit replacement for the following part numbers:

• Firestone: W01-358-9978, W01-358-6262, W01-358-6231, 9978, 99978, 6262, 6231
• Hendrickson: S28929, S-28929, C28929, HENS-28929
• Goodyear: 1R12-668, 1R12-1179, GYR1R12668, GYR-1R12-668, 8235FS9978
• Continental / ContiTech: 910-14P959, 910-17.5P831, 67588, 77303
• Automann: 566.CT67588, AB1DK23I-A959, AB1DK23I-P959, AB1DK23P-6262
• Meritor: FS9978, FS6262, FS6231
• Other Aftermarket: TR9978 (Torque), AS-9978 (Triangle), 352-9978 / 452-9978L (Dayton), N32 559978 (Alliance), S28501 (Newstar)

Technical Specifications

• Top Plate Diameter: 9.00"
• Top Plate Hardware: 2 Bolt Holes (5.5" Center-to-Center)
• Bottom Plate Diameter: 10.24"
• Bottom Plate Hardware: 1 Bolt Hole (2.25" Center-to-Center)
• Extended Length: Approx. 19.6" - 22.00"
• Compressed Length: Approx. 7.8" - 8.20"
• Piston Width: 8.05"
• Warranty: 3-Year Unlimited Mile
• Brand: FleetPro Parts & Tires