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What You Need to Know About SAE J339: Webbing Abrasion and Tilt Lock Testing (Cancelled)
SAE J339, originally issued in 1968, defined test methods for webbing abrasion and tilt lock performance of two-point adjust tongues used in seat belt hardware. The standard applied to passenger cars and multi-purpose vehicles. However, due to the declining use of two-point adjust tongues in new vehicles and the existence of SAE J386 for off-road applications, J339 was cancelled in June 2013. This article provides an overview of the standard, the reasons for its cancellation, and guidance for engineers working on seat belt systems today.
What Was SAE J339?
SAE J339 was a Surface Vehicle Recommended Practice that provided specific test procedures for evaluating the durability and safety of two-point adjust tongues. The key tests included:
- Webbing Abrasion Test: Simulated wear to ensure the webbing could withstand repeated rubbing against the tongue.
- Tilt Lock Performance Test: Verified that the tongue could lock properly when tilted, preventing unwanted movement.
These tests were crucial for ensuring that two-point belt systems would function reliably over time. The standard was maintained by the SAE Belt Systems Standards Subcommittee and reviewed periodically until its cancellation.
⚠️ Standard Status: SAE J339 was cancelled in June 2013. It is no longer maintained or recommended for use in new vehicle designs. However, it may serve as a historical reference for legacy systems or educational purposes.
Why Was J339 Cancelled?
The rationale for cancellation is clearly stated in the document: two-point adjust tongues are currently used in very few new passenger cars and multi-purpose vehicles. FMVSS regulations allow a 2-point belt only at the front center seating position, and that position is rare in modern vehicles. As a result, abrasion from two-point adjust tongues is not a significant concern in new vehicles.
Additionally, the SAE Belt Systems Standards Subcommittee’s scope is new passenger cars and multi-purpose vehicles, so J339 and its companion performance standard SAE J114 were deemed no longer necessary for that scope. For off-road and off-highway vehicles that still use two-point adjust tongues, SAE J386 provides appropriate requirements.
What Standards Should Engineers Use Now?
For engineers involved in seat belt design and testing, it is important to use active standards. The following table summarizes the key documents:
| Standard | Title | Application | Status |
|---|---|---|---|
| SAE J339 | Seat Belt Hardware Webbing Abrasion Test Procedure | Two-point adjust tongues in passenger cars and MPVs | Cancelled (2013) |
| SAE J114 | Seat Belt Hardware Performance Requirements | Two-point adjust tongues (performance) | Cancelled (2013) |
| SAE J386 | Seat Belt Hardware – Off-Highway Vehicles | Two-point adjust tongues in off-road vehicles | Active |
Engineering Design Insight 🛠️: When working with two-point adjust tongues for off-highway applications, always reference SAE J386 for both abrasion and tilt lock requirements. For passenger vehicles, the need for two-point belt testing is largely obsolete; focus on three-point belt standards and FMVSS compliance. If maintaining legacy systems, J339 can serve as background but should not be used for certification of new products.
⚠️ Important: Do not assume J339 is still active. Using a cancelled standard can lead to non-compliance and safety issues. Always verify the latest standards from SAE or regulatory bodies.
Frequently Asked Questions
Is SAE J339 still valid for testing?
No. SAE J339 was cancelled in June 2013 and is not recommended for use. It has been superseded by active standards for specific applications, such as SAE J386 for off-highway vehicles.
What vehicles were covered by J339?
The standard applied to passenger cars and multi-purpose vehicles (MPVs). It specifically addressed two-point adjust tongues used in seat belt systems.
Can J339 be used for three-point seat belts?
No. J339 is specifically for two-point adjust tongues. Three-point belt systems have different hardware and test requirements. Refer to standards such as SAE J114 (which is also cancelled) or active FMVSA test procedures.
What should I use instead of J339 for off-road vehicles?
For off-highway vehicles, use SAE J386, which covers abrasion and tilt lock performance for two-point adjust tongues in those environments. Always check the latest revision.
