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Within the critical drum brake system of a commercial vehicle, numerous components must work in perfect harmony to ensure safety. As a premier supplier of durable and reliable Foton truck parts, we detail the essential Retracting Spring, bearing the official OEM number QDT3502012-LB. This specific spring variant is engineered for particular FOTON truck models, providing the calibrated tension required to retract the brake shoes efficiently after each application. The performance of spring QDT3502012-LB is fundamental to preventing residual drag, minimizing wear, and maintaining the precise clearance necessary for optimal brake function and fuel efficiency.
Retracting Spring (English)
Возвратная пружина тормозной колодки (Russian)
Muelle de Retracción (Spanish)
The Retracting Spring with part number QDT3502012-LB performs the vital task of resetting the brake shoes. When the driver releases the brake pedal, hydraulic pressure in the wheel cylinder drops. Immediately, the stored energy in this spring pulls the shoes back from the drum surface.
This action is not passive; it is an active and positive return. It establishes a defined air gap between the friction lining and the drum, eliminating contact during non-braking driving. This precise function, performed by spring QDT3502012-LB, is what prevents the constant friction that leads to drag, overheating, and premature component failure.
Without a spring of the correct specification, the shoes could remain partially applied due to residual hydraulic pressure, mechanical stickiness, or minor corrosion, silently costing the operator in fuel and repair bills while compromising safety margins.
The QDT3502012-LB component is a testament to precision engineering. It is a helical tension spring, where the wire diameter, coil diameter, pitch, and number of coils are all variables meticulously defined by FOTON’s design parameters.
The spring material, typically a high-carbon or chrome-silicon alloy steel, is chosen for its excellent yield strength and ability to return to its original length after deflection. The manufacturing process includes stress-relieving and preset treatments to lock in the spring’s memory and prevent relaxation under load.
The end hooks are formed to specific angles and radii to ensure they seat properly against the brake shoe web and the anchor pin, distributing stress evenly and preventing points of high wear or potential hook straightening.
A compromised retracting spring, such as a weakened or broken QDT3502012-LB, manifests through several symptoms. The most common is brake drag, where the vehicle feels sluggish and fuel consumption noticeably increases.
Upon stopping, one may detect a distinct burning smell from a particular wheel. The wheel hub or drum on that axle will be significantly hotter than the others after a drive. In advanced cases, the affected brake may smoke.
The long-term consequences are severe: rapid and uneven lining wear, glazing of the friction material, scoring and potential heat-checking (cracking) of the brake drum, increased bearing grease breakdown, and in extreme scenarios, a wheel fire. Therefore, the spring, part number QDT3502012-LB, is a small but vital safety item.
This table provides the definitive technical data for the genuine FOTON Retracting Spring. Use this information for accurate parts verification and technical reference.
| Parameter | Specification | Description / Standard |
|---|---|---|
| OEM Part Number | QDT3502012-LB | Official FOTON Identification |
| Product Name | Retracting Spring | Brake Shoe Return Spring |
| Brand | FOTON | Original Equipment |
| Spring Type | Helical Tension Spring | With closed and ground ends |
| Core Material | High-Carbon Spring Steel | SAE 1060-1090 or equivalent |
| Surface Treatment | Zinc Plated or Phosphated | For corrosion resistance |
| Application | Drum Brake System | Specific FOTON truck models |
| Function | Active Shoe Retraction | Prevents drag, ensures clearance |
Replacing the retracting spring QDT3502012-LB requires proper tools and safety procedures. The vehicle must be securely lifted, the wheel removed, and the brake drum taken off to access the shoe assembly.
Specialized brake spring pliers are highly recommended for safe removal and installation. This prevents injury from a spring slipping under tension and ensures the new spring is seated correctly. The hooks of the new QDT3502012-LB spring must engage the designated holes in the brake shoe and the anchor pin fully.
It is crucial to clean the anchor pin and shoe contact points and apply a thin layer of high-temperature brake lubricant. This reduces friction, allowing the spring to work efficiently and preventing premature wear. Always replace springs in axle pairs to maintain balanced braking force and retraction across the vehicle.
After reassembly, manually adjust the brake shoes (if equipped with a manual adjuster) to the correct running clearance before installing the drum. Spin the wheel by hand to verify it rotates freely without any drag or scraping sounds.
Incorporate spring inspection into your regular brake maintenance schedule to avoid unexpected failures of part QDT3502012-LB.
Visual Inspection Criteria: Look for rust penetration (light surface rust may be acceptable, but scaling is not), discoloration from extreme heat (blueing), reduced coil diameter, or any deformation of the hooks or coils.
Comparative Tension Test: While subjective, a side-by-side comparison with a new QDT3502012-LB spring can reveal significant loss of tension. The old spring may feel noticeably “softer” when stretched.
Systematic Diagnosis: If brake drag is suspected, a non-contact infrared thermometer can quickly identify a hotter wheel hub after a short drive, pinpointing the problematic axle for further inspection.
Preventive Replacement Policy: Consider replacing all retracting springs every second major brake service (e.g., every other lining change) as a cost-effective preventive measure. The spring part number QDT3502012-LB is inexpensive compared to the cost of a ruined drum or a roadside breakdown.
The Retracting Spring, OEM QDT3502012-LB, is a quintessential example of a component where OEM specification is non-negotiable for optimal performance. Its precise tension and fit are integral to the brake system’s health.
Choosing the genuine FOTON part ensures your truck’s brakes release as designed, protecting your investment from the hidden and costly effects of drag. It contributes directly to vehicle safety, component longevity, and operating economy.
Never compromise on the quality of brake return components. Insist on the authentic QDT3502012-LB spring for all your FOTON brake servicing needs. Rely on our comprehensive inventory of verified OEM and quality replacement parts to maintain your fleet’s performance, safety, and reliability at the highest standard.
If you have any questions about our products, services, or anything related to what we offer, please don’t hesitate to leave us a message—our dedicated team is always ready to provide prompt and helpful responses to address your concerns. What’s more, when you become our valued customer, we’re delighted to offer you complimentary catalog services, giving you access to detailed, up-to-date information on our full range of products, specifications, and offerings to help you make informed decisions.
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