Measuring Threads: Why We Use Imperial Fittings
At AirRide, we exclusively use imperial fittings in our air suspension systems. While metric fittings might seem like the modern choice, imperial fittings remain the standard in the air suspension industry for good reason.
Why Imperial Fittings Dominate the Market
The air suspension market is heavily influenced by U.S.-based manufacturers, where imperial fittings are the norm. Many of the world’s leading air suspension brands, including AirLift, Viair, and Firestone, design their components with imperial threads. As a result:
- Consistency Matters: Mixing imperial and metric threads can lead to compatibility issues, making imperial fittings the logical choice for aftermarket systems.
- Firestone Legacy: One of the oldest air bag manufacturers, Firestone, primarily uses imperial threads. Many air springs are still designed to match the original Firestone specifications, ensuring widespread compatibility.
Understanding NPT Threads
The majority of air suspension systems use NPT (National Pipe Taper) threads. These are a specific type of imperial thread that offers excellent sealing properties.
- What is NPT? NPT stands for National Pipe Taper. The tapering design enhances sealing by allowing the threads to compress slightly as they tighten.
- Sealing Properties: While NPT threads are theoretically capable of sealing without additional materials, thread sealant or tape is essential in practice to ensure a leak-free connection.
NPT vs. BSP Threads
While NPT and BSP (British Standard Pipe) threads may look similar, they are not interchangeable:
- Dimensional Differences: NPT and BSP threads differ in their pitch, angle, and diameter, making them incompatible.
- Sealing Issues: BSP threads are often straight and require additional washers for sealing, whereas NPT threads rely on their taper for a tighter fit.
How to Measure Threads
Accurate measurement of thread size is essential for selecting the correct fittings. Here’s what you need to know:
- Tools Required: Use a thread pitch gauge, thread caliper, and depth gauge for precise measurements.
- Common NPT Sizes: 1/8 NPT, 1/4 NPT, 3/8 NPT, and 1/2 NPT are the most widely used, with 1/4 NPT being the most common in air suspension systems.
- Avoid Misconceptions: The measured outside diameter (OD) or inside diameter (ID) does not directly match the named thread size. For example, a 1/4 NPT fitting has an OD of approximately 12.5mm, which can confuse those unfamiliar with nominal bore measurements.
Choosing the Right Fittings
Fittings come in various styles and sizes to suit different applications:
- Male and Female Fittings: These refer to the external or internal threading of the component.
- Straight vs. 90-Degree Fittings: All AirRide 90-degree fittings are 360-degree swivels, allowing for easy adjustment even when tightened. Fixed 90-degree fittings are not recommended, as they often align poorly during installation.
Our standard fittings are designed for 1/4 Push-To-Connect (PTC) airlines, but we also stock fittings for 1/8, 3/8, and 1/2 PTC hoses.
Why Quality Matters
At AirRide, we prioritize quality in every product we supply:
- Leak-Free Performance: Our fittings undergo extensive testing to ensure they meet the highest standards of reliability.
- Rigorous Testing Process: Every new product is first tested on our own vehicles for up to a year. If it meets our standards, it is installed in our workshop before being made available to customers.
- Rejecting Low-Cost Alternatives: While we frequently receive offers for cheaper fittings, they often fail to seal properly, compromising the entire system.
