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In the intricate world of commercial vehicle braking systems, every component plays a vital role in safety and performance. As a trusted source for essential Foton truck parts, we present the critical Retracting Spring, identified by the OEM part number QDT3502049-LB. This high-tension spring is a key element within the drum brake assembly of many FOTON trucks, responsible for swiftly and consistently pulling the brake shoes away from the drum after braking pressure is released. The reliable function of spring QDT3502049-LB prevents brake drag, reduces wear, and ensures optimal clearance for efficient vehicle operation.
Retracting Spring (English)
Возвратная пружина (Russian)
Resorte de Retracción (Spanish)
The primary duty of the Retracting Spring, part number QDT3502049-LB, is to provide a reliable return force. When the brake pedal is released and hydraulic pressure drops, this spring’s tension overcomes any residual friction or stickiness, actively pulling the brake shoes back to their resting position.
This action creates a precise and consistent running clearance between the brake lining and the drum. Without a fully functional spring, the shoes might remain partially applied, causing constant friction known as brake drag. This condition leads to excessive fuel consumption, accelerated wear on linings and drums, and potential overheating of the entire brake assembly.
The spring is a critical safety component, ensuring the braking system is ready for the next application and preventing unintended partial braking that could compromise vehicle control.
The QDT3502049-LB spring is a coil-type tension spring, typically made from high-grade spring steel wire. Its design includes specific end hooks or loops that are shaped to attach securely to designated points on the brake shoe and the fixed anchor within the backing plate.
The wire diameter, coil diameter, number of active coils, and free length are all calculated to produce the exact force required for the specific brake shoe weight and geometry of the FOTON truck model it serves. Using a spring with incorrect tension, such as a non-OEM substitute, can lead to poor retraction or over-retraction, which may cause uneven lining contact.
The spring is often coated or treated to resist corrosion from road salts, moisture, and brake dust, which can otherwise lead to premature failure through rust-induced weakening or seizing.
A worn, stretched, or broken retracting spring, including part QDT3502049-LB, leads directly to brake drag. The symptoms are noticeable and costly.
The driver may feel reduced vehicle performance and fuel efficiency as the engine works harder to overcome the constant braking force. The affected wheel hub may become excessively hot to the touch after driving, even without aggressive braking.
Prolonged drag causes rapid, uneven wear of the brake linings and can score or overheat the brake drum, potentially leading to thermal cracking. In severe cases, the excessive heat can boil brake fluid, degrade wheel bearings, and pose a significant fire risk.
Regular inspection and timely replacement of the retracting spring are therefore critical preventive maintenance tasks.
The table below details the core technical parameters for the genuine FOTON Retracting Spring. This data is crucial for correct identification and understanding its role in the brake system.
| Parameter | Specification | Details / Notes |
|---|---|---|
| OEM Part Number | QDT3502049-LB | Genuine FOTON Identification |
| Product Name | Retracting Spring | Brake Shoe Return Spring |
| Brand | FOTON | Original Equipment Manufacturer |
| Spring Type | Tension Coil Spring | With formed end hooks |
| Primary Material | High-Carbon Spring Steel | Often with anti-corrosion coating |
| Application | Drum Brake Assembly | For specified FOTON truck models |
| Function | Shoe Retraction | Prevents brake drag, ensures clearance |
| Installation Position | Upper or Lower Anchor | Connects shoe to fixed backing plate anchor |
Replacing the retracting spring QDT3502049-LB is typically done during a brake relining service. Safety is paramount: the truck must be securely lifted and supported, with the wheels and brake drums removed.
Using proper brake spring tools is essential to safely remove the old spring and install the new one. The hooks must be correctly seated on the brake shoe and anchor pin. Incorrect installation can lead to the spring popping off under tension or interfering with other components.
It is highly recommended to replace all retracting springs on an axle at the same time, even if only one appears weak. This ensures balanced brake function. Always lubricate the anchor pin and contact points with high-temperature brake grease to ensure smooth shoe movement and prevent premature spring fatigue.
After installing the new QDT3502049-LB spring and reassembling the brake, manually adjust the shoe clearance (if applicable) and perform a functional test to ensure the wheels spin freely without drag before road testing.
Regular inspection of the retracting spring QDT3502049-LB can prevent unexpected failures.
Visual Inspection: During brake service, check for signs of corrosion, rust scaling, or physical damage like stretched coils or deformed hooks. Compare the installed length and tension with a new spring.
Functional Test: With the drum removed, apply and release the brake manually (using the lever or wedge). Observe if both shoes retract smoothly and evenly. A sluggish or uneven return indicates a weak spring or binding components.
Symptom Awareness: Be alert to driver reports of reduced fuel mileage, a burning smell from wheel areas, or excessive heat from a hub. These are classic indicators of brake drag potentially caused by a failed QDT3502049-LB spring.
Preventive Replacement: As a wear item with a finite fatigue life, consider replacing retracting springs as part of a major brake overhaul or every second lining change to ensure consistent performance.
The Retracting Spring, OEM part QDT3502049-LB, may be small and inexpensive, but its role is disproportionately large. It is the definitive component that ensures your FOTON truck’s brakes disengage completely, protecting your investment from the hidden costs of drag.
Choosing the genuine FOTON part guarantees the correct mechanical properties, fit, and durability. This ensures reliable shoe retraction, maximizes the lifespan of expensive friction components, and contributes to overall vehicle safety and efficiency.
Do not overlook this critical component during brake maintenance. Insist on the authentic QDT3502049-LB spring to maintain the designed performance and safety of your FOTON truck’s braking system. For all your service needs, rely on our comprehensive selection of OEM-quality parts to keep your fleet operating at its peak.
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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