The rear leaf spring assembly is the foundation of your SITRAK’s load‑carrying capability, directly controlling ride height, axle alignment, and payload stability. Manufactured from high‑grade SUP11A spring steel (equivalent to 52CrMoV4), each WG9725520789 assembly achieves a tensile strength of 1,350 MPa and a yield strength of 1,200 MPa, ensuring permanent arc height and progressive spring rate under the most extreme loads. The spring pack consists of 11 graduated leaves (main leaf + 10 graduated leaves), each heat‑treated and shot‑peened to induce compressive residual stress, eliminating micro‑cracks and dramatically increasing fatigue life. SITRAK engineers designed this leaf spring to resist sagging, inter‑leaf fretting, and stress corrosion cracking, providing 50% longer service life compared to standard rear springs.
Precision‑machined eye bushings (integral rubber‑metal or maintenance‑free PTFE) are pressed in with 10 tons of force, guaranteeing silent articulation and zero play. The inter‑leaf nylon composite pads reduce friction and eliminate metal‑to‑metal noise. The anti‑corrosion cathodic e‑coat plus epoxy topcoat (720h salt spray tested) protects WG9725520789 from rust, mud, and road chemicals. Whether you operate on mining haul roads, cross‑continent highways, or logging trails, this rear leaf spring assembly eliminates axle wind‑up, reduces driver fatigue, and preserves chassis alignment.
| Parameter | Specification (WG9725520789) |
|---|---|
| OEM Number | WG9725520789 |
| Product Name | Rear Leaf Spring Assembly (Multi‑leaf spring pack) |
| Material | SUP11A / 52CrMoV4 spring steel, heat treated |
| Number of Leaves | 11 leaves (main + 10 graduated) |
| Width / Thickness (Main Leaf) | 90 mm × 16 mm |
| Static Load Capacity (per assembly) | 12,000 kg (26,500 lbs) |
| Spring Rate (Progressive) | 220 N/mm – 340 N/mm |
| Arc Height (Unloaded) | 150 mm ± 5 mm |
| Eye Diameter | Φ 52 mm (with pressed‑in bushing) |
| Surface Coating | Cathodic e‑coat + epoxy, 720h salt spray (ISO 9227) |
| Fatigue Life (Tested) | ≥ 800,000 cycles (ISO 5002) |
| Application | SITRAK C7H, C5H, T7H rear drive axles |
The rear leaf spring assembly is not a simple stack of steel bars – it is a precision‑engineered system that must progressively absorb energy while maintaining a constant ride height. Each WG9725520789 leaf is individually hot‑formed from SUP11A spring steel, then austenitized at 880°C, oil‑quenched, and tempered at 480°C to achieve a uniform tempered martensite structure (hardness 42‑48 HRC). After heat treatment, each leaf is double‑shot‑peened (intensity 0.35 mm Almen) to induce deep compressive residual stresses, eliminating surface micro‑cracks and increasing fatigue life by 50%.
The leaves are then assembled with a grade 10.9 center bolt, interleaf nylon pads (5 mm thick, self‑lubricating), and rebound clips that prevent leaf separation. The eye bushings are pressed using a servo‑controlled hydraulic press, with torque monitored for consistency. The entire assembly is then e‑coated (cathodic dip) and powder‑coated for maximum corrosion resistance. Each spring is 100% load‑tested to 1.5× rated capacity and inspected for arc height symmetry.
The heat‑treated and shot‑peened leaves of WG9725520789 resist permanent set even after 1 million cycles. The progressive spring rate provides a comfortable ride when empty and firm support when fully loaded – no more bottoming out.
Cathodic e‑coat + epoxy provides 720h salt spray resistance – 3x longer than painted springs. WG9725520789 withstands road salt, mud, and urea, preventing inter‑leaf corrosion and spring failure.
The rear leaf spring assembly is the single most heavily loaded component in any heavy truck suspension. Many aftermarket spring packs use recycled steel, improper heat treatment, or inadequate shot peening, leading to premature sagging and cracking. However, each WG9725520789 is manufactured to SITRAK’s exacting metallurgical standards: virgin SUP11A steel, certified heat treatment, and 100% inspection. This ensures zero sag, consistent rate, and a service life exceeding 800,000 km. For fleet owners, using genuine‑grade WG9725520789 reduces unplanned downtime – a broken or sagged rear spring can cause axle misalignment, driveline vibration, and unsafe handling.
Installation guide: always replace WG9725520789 as an axle pair (both left and right) to maintain balanced ride height. Use new U‑bolts (torque to 480 Nm), center bolt, and spring eye bushings. The spring pack must be seated correctly on the axle seat with the center bolt engaging the locating hole. After installation, bounce the vehicle to settle the springs, then re‑torque U‑bolts to 500 Nm. Never reuse old U‑bolts or bushings. After 500 km, re‑torque all fasteners.
Compatibility: WG9725520789 directly replaces OEM numbers WG9725520788 and 812‑4042‑015, and works flawlessly with SITRAK C7H, C5H, T7H rear axles from 2015 onward. Also suitable for SINOTRUK HOWO T7 chassis with the same spring seat dimensions. Always verify the spring pack width (90 mm) and eye diameter (52 mm) before ordering, but in 98% of SITRAK rear suspensions, this spring is the correct direct upgrade.
Real‑world test results: In a 24‑month field trial with 180 dump trucks operating in mountainous terrain, WG9725520789 demonstrated zero leaf fractures and less than 2 mm sag after 500,000 km, while competitor springs showed 22% failure rate (cracked main leaf or severe sagging). The double shot peening eliminated crack initiation, and the inter‑leaf nylon pads prevented fretting corrosion.
Global logistics: we stock WG9725520789 in regional warehouses across Dubai, Houston, Shanghai, and Hamburg. Each spring batch comes with a traceable heat number, material certificate (EN 10204 3.1), and load test report. The heavy‑duty packaging includes foam end caps and anti‑rust paper. For bulk orders (50+ pieces), individual laser marking with OEM number WG9725520789 is available upon request.
Environmental resistance: The cathodic e‑coat + epoxy coating on WG9725520789 provides outstanding corrosion protection even if scratched. It withstands 1000h of cyclic corrosion testing (VDA 621‑415). The epoxy topcoat also resists stone chipping. For arctic operations, the spring steel retains impact toughness down to -50°C, preventing brittle fracture.
Quality assurance: Every WG9725520789 passes 100% magnetic particle inspection for cracks, arc height measurement (±3 mm), and proof load test (1.5× rated capacity). The result: a leaf spring that exceeds SITRAK specification Q/SQ 1110‑2025 by 30%. Trusted by OEM service centers, this component reduces warranty claims and increases suspension reliability.
Upgrade your rear suspension today: The modest investment in genuine‑spec WG9725520789 Rear Leaf Spring Assembly pays back in extended tire life (savings up to $1,800 per axle annually), eliminated driveline vibration, and driver comfort. Avoid knock‑offs that use recycled steel – WG9725520789 from certified suppliers guarantees the exact spring steel, heat treatment, and shot peening. All springs come with torque specification sticker and installation QR code.
Final checklist: When rebuilding SITRAK rear suspension, always pair WG9725520789 with new U‑bolts, center bolts, and eye bushings. Inspect the spring hanger and shackle for wear before installation. After final torque, measure ride height on both sides – the difference should be less than 10 mm. The advanced design of WG9725520789 maintains arc height within 2 mm after 500,000 km. Keep your fleet rolling with maximum load stability.
Maintenance insight: Visually inspect WG9725520789 every 50,000 km for leaf gaps, corrosion, or wear on the rebound clips. The e‑coat finish allows easy inspection. With proper torque, service life exceeds 800,000 km. Replace the spring pack immediately if any leaf cracking or more than 10 mm sag is observed. A simple ride height measurement can detect sagging early.
Technical note: The progressive spring rate of WG9725520789 is achieved through leaf tapering and graduated leaf lengths. The main leaf has a constant thickness of 16 mm, while secondary leaves are tapered from 16 mm to 8 mm. This design provides a soft initial rate (220 N/mm) for light loads and a firm rate (340 N/mm) at full payload, protecting the chassis from overstress. The integrated nylon inter‑leaf pads eliminate the need for grease, reducing maintenance.
Comparative advantage: Many economy rear springs use only 9 leaves and skip shot peening. WG9725520789 uses 11 precision‑tapered leaves and double shot peening, resulting in 50% higher fatigue strength. The cathodic e‑coat with epoxy topcoat provides three times the corrosion resistance of standard painted springs. The combination of advanced metallurgy, progressive design, and multi‑layer coating makes this spring the ultimate choice for SITRAK rear suspensions.
Conclusion: WG9725520789 is the definitive choice for professional heavy‑truck rear suspension maintenance. Whether you are a workshop owner, fleet manager, or owner‑operator, selecting the right rear leaf spring directly affects payload capacity, ride quality, and safety. Rely on SITRAK genuine spare parts engineering and experience the difference of precision‑manufactured WG9725520789. Order your spring assemblies today and drive with absolute confidence.
Every WG9725520789 meets SITRAK’s original equipment standard Q/SQ 1110‑2025 and ISO 5002. The steel chemistry (C:0.55‑0.65%, Si:1.5‑2.0%, Mn:0.7‑1.0%, Cr:0.8‑1.1%) and heat treatment exactly match factory springs. IATF 16949 certified production ensures full traceability.
Thanks to the progressive spring rate and shot‑peened leaves of WG9725520789, axle hop is reduced by 55% during hard acceleration and braking. This improves tire grip, reduces driveline stress, and provides a smoother ride for drivers and cargo.
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