Product Introduction

Structure

This leaf spring center bolt is a precision-machined alloy steel fastener designed for heavy-duty truck leaf spring suspension systems. It features a hexagonal flange head for enhanced clamping force, a smooth cylindrical shank, and a precision-threaded end. The entire component is finished with a zinc-plated passivation coating, which imparts a metallic, iridescent appearance and provides excellent corrosion resistance.

Performance

Manufactured from high-grade alloy steel (e.g., 42CrMo) and subjected to controlled heat treatment, this bolt achieves a tensile strength grade of 12.9, exhibiting exceptional fatigue resistance and yield strength. It is designed to withstand the extreme dynamic loads, impacts, and torsional forces encountered in heavy-duty operation, maintaining structural integrity in temperatures ranging from -40°C to 120°C. The zinc-plated passivation coating provides superior protection against rust, salt spray, and chemical exposure, ensuring long-term durability in diverse operating environments. The precision-machined threads ensure a tight, secure fit, minimizing play and ensuring consistent performance.

Core Function

1. Serves as a critical fastening component for leaf spring assemblies, clamping the multiple steel leaves together and maintaining their alignment and structural integrity.

2. Transmits and distributes complex loads such as vertical pressure, lateral torque, and longitudinal impact from the leaf spring to the chassis, maintaining the integrity of the suspension system.

3. Maintains precise alignment of the leaf spring leaves, preventing relative displacement under dynamic conditions such as vehicle acceleration, braking, and turning, avoiding abnormal wear of suspension parts.

Leaf Spring Center Bolt AZ9725520360 for SINOTRUK Heavy-Duty Trucks

When your leaf spring assembly loses its grip, the entire suspension system pays the price. The Leaf Spring Center Bolt AZ9725520360 is engineered specifically for SINOTRUK heavy-duty vehicles, serving as the critical fastener that holds your multi-leaf spring pack together and keeps it precisely aligned on the axle seat. Built to endure extreme loads, road vibrations, and harsh operating conditions, this center bolt ensures your suspension stays tight, stable, and road-ready — mile after mile.

At Mettlead, we supply this genuine-spec center bolt directly from our factory in China, which means you get OEM-matching quality at a competitive wholesale price. Whether you manage a fleet of SINOTRUK trucks or run a parts distribution business, this bolt is a small component that makes a massive difference in vehicle safety and longevity.

Key Features and Benefits of AZ9725520360 Center Bolt

Every detail of this leaf spring center bolt is designed with one goal in mind: keeping your SINOTRUK’s suspension assembly locked in place under the toughest conditions. Here is what sets it apart:

• Precision OEM Fitment — Manufactured to match the exact dimensions and tolerances of the original SINOTRUK specification, so installation is seamless with no modifications required.
• High-Strength Steel Construction — Forged from premium-grade steel that resists shearing, fatigue, and deformation even under continuous heavy payloads.
• Corrosion-Resistant Surface Treatment — Treated with a protective coating to withstand moisture, road salt, and chemical exposure, extending service life significantly.
• Vibration Dampening Stability — Keeps the entire leaf spring pack clamped tightly together, preventing lateral shifting that can lead to uneven tire wear and compromised handling.
• Cost-Effective Maintenance Solution — Replacing a worn center bolt early prevents cascading damage to leaf springs, U-bolts, and axle seats — saving you far more in the long run.

In short, this is not just a bolt. It is the backbone of your leaf spring assembly, and choosing the right one protects your entire chassis investment.

Application Scenario: Where This Center Bolt Works

The Leaf Spring Center Bolt AZ9725520360 is specifically designed for SINOTRUK heavy-duty vehicles equipped with multi-leaf spring rear and front suspension systems. Its primary function is to fasten the entire group of leaf spring plates together at the center point, while simultaneously locating the spring pack on the axle seat through the locating hole.

Compatible Vehicle Range:

• SINOTRUK HOWO series heavy trucks
• SINOTRUK SITRAK series vehicles
• SINOTRUK Steyr-platform models
• Other SINOTRUK chassis variants using the AZ9725520360 specification

By clamping the full leaf spring assembly and ensuring structural alignment, this center bolt guarantees that the suspension behaves as a unified system — absorbing road shocks evenly, maintaining ride height, and protecting the frame from stress fractures. If your trucks operate on rough terrain, carry heavy cargo, or run long-haul routes, this bolt works overtime to keep everything together.

Looking for more SINOTRUK suspension and chassis components? Browse our full Chassis Parts Category or explore the complete SINOTRUK HOWO Truck Parts collection.

Technical Specifications

Below you will find the detailed parameters for the AZ9725520360 Leaf Spring Center Bolt. These specifications ensure you can verify fitment and compatibility before placing your order.

Note: If you need to cross-reference this part number with your vehicle’s VIN or chassis code, our technical team is happy to assist with verification.

OEM/ODM Capability and Custom Packaging

Mettlead understands that different markets have different requirements. That is why we offer flexible manufacturing and branding solutions tailored to your business needs:

• White-Label Packaging — Receive products in neutral packaging, ready for your own branding and distribution channels.
• Custom Packaging — We can print your logo, part numbers, and brand identity directly on the packaging for a professional market presence.
• Strict Quality Control — Every batch undergoes dimensional inspection, hardness testing, and surface quality checks before shipment. We do not cut corners on QC.
• Bulk Order Flexibility — Whether you need 100 pieces or 10,000, our production capacity scales to meet your demand with consistent lead times.
• Factory Visit Welcome — We encourage procurement managers to visit our facility in China to inspect production lines and quality processes firsthand.

In other words, you are not just buying a bolt — you are gaining a reliable supply chain partner who adapts to your market requirements.

Frequently Asked Questions (FAQ)

What does a leaf spring center bolt actually do?

The center bolt passes through the center hole of all leaf spring plates, clamping them together as a single unit. Additionally, it fits into a locating hole on the axle seat, which prevents the spring pack from shifting forward or backward during operation. Without a properly functioning center bolt, the leaf springs can splay apart or misalign, leading to dangerous handling issues.

How do I know if my center bolt needs replacement?

Common signs include clunking noises from the suspension, visible lateral movement of the leaf spring pack, uneven tire wear, or a broken/sheared bolt discovered during routine inspection. If the bolt head appears rounded, cracked, or corroded beyond its protective coating, replacement is strongly recommended before further damage occurs.

Is AZ9725520360 compatible with all SINOTRUK models?

This part number is designed for SINOTRUK vehicles that use the AZ9725520360 specification in their leaf spring assembly. It fits most HOWO, SITRAK, and Steyr-platform trucks. However, since SINOTRUK produces various chassis configurations, we recommend confirming your vehicle’s chassis number with our team to ensure a perfect match.

Can I use a generic center bolt instead of the OEM-spec part?

While generic bolts may physically fit, they often lack the precise hardness grade, thread pitch, and dimensional accuracy required for heavy-duty applications. A substandard center bolt can shear under load, which is a serious safety hazard. The AZ9725520360 meets OEM specifications, giving you the reliability your trucks demand.

What is the recommended torque specification for installation?

Torque values depend on the specific vehicle model and leaf spring configuration. Generally, SINOTRUK service manuals specify the torque for center bolt nuts. We recommend following the manufacturer’s workshop manual for your exact model. If you need guidance, our technical support team can help you locate the correct specification.

How should I store center bolts before installation?

Store them in a dry, ventilated environment away from direct moisture and corrosive chemicals. Keep the protective coating intact by leaving bolts in their packaging until ready for use. Proper storage ensures the anti-corrosion treatment remains effective and the bolt performs as intended during installation.

Ready to Secure Your Supply? Get a Quote Today

Your trucks depend on every component working in harmony, and the Leaf Spring Center Bolt AZ9725520360 is no exception. Whether you are restocking your warehouse, fulfilling a fleet maintenance schedule, or sourcing parts for a new market, Mettlead delivers factory-direct pricing, fast shipping, and the quality assurance your business deserves.

Take the next step:

• Request a competitive bulk quote with volume-based pricing
• Ask about custom packaging options for your brand
• Verify part compatibility with your specific vehicle models

Contact Us Now to speak with our parts specialists and get your order moving. You can also explore our full range of SINOTRUK Truck Parts to find everything you need in one place.