How to Measure a Trailer Axle 3

How to Measure a Trailer Axle: A Comprehensive Guide

Ordering a new trailer axle? The accuracy of your measurements can’t be overstated. An incorrect size not only leads to wasted time and resources but could also affect the safety and performance of your trailer. Here’s a detailed guide to ensure you get those measurements right, even if you’re working with a bent axle.

Why Accurate Measurements Matter

Accurate measurements ensure that the new axle fits perfectly, aligning with the wheels and the frame of the trailer for optimal performance. Misalignment can lead to uneven tire wear, poor handling, and potentially dangerous towing situations.

Tools You’ll Need

• A reliable tape measure
• A straight edge or level
• A notepad and pen for recording your measurements

Understanding Key Measurements

1. Hub Face Measurement

The hub face measurement is crucial. It’s the distance from the face of one hub to the face of the opposite hub. This measurement is taken from where the back of the wheel sits against the face of the hub. It determines the width of the axle and ensures your wheels sit properly under your trailer. View the image provided below, which illustrate examples of a hub face on four distinct axles. The hub face is emphasized in red.

2. Spring Center Measurement

This is the distance between the centers of the spring pads, where the axle connects to the trailer’s leaf springs. Accurately measuring the spring center can help you confirm that the new axle will align correctly with your trailer’s suspension system. Typically adding 2 inches to this measurement can also provide an estimate for the frame width. See spring center diagram below.

Additional Considerations

Axle Beam Diameter

• For 3,500 lb axles, the standard round tube axle beam diameter is 2 3/8 inches.
• Axles ranging from 5,200 lb to 7,000 lb usually have a 3-inch diameter.
• See diagram below. Measure from top of beam to bottom, Use calipers for precise measurement.

Bolt Pattern

• 3,500 lb axles commonly have a 5 lug bolt pattern, with the most prevalent being 5 lug on a 4.5-inch pattern. However, there are four different 5 lug patterns to be aware of.
• For 5,200 lb axles, a 6 lug on a 5.5-inch bolt pattern is typical.
• 7,000 lb axles often come with an 8 lug on a 6.5-inch bolt pattern.

Understanding how to measure your bolt pattern is crucial, especially for the 5 lug configuration due to its variations. Check out our blog on How to Measure a 5 Lug Trailer Axle Bolt Pattern here.

Step-by-Step Guide to Measuring

1. Prepare Your Trailer: Ensure it’s on a level surface and safely secured.
2. Measure the Hub Face: Use the tape measure to find the distance from one hub face to the opposite hub face.
3. Measure the Spring Center: Measure the distance between the centers of the spring pads.
4. Note the Axle Beam Diameter: This might require a caliper for precise measurement.
5. Identify the Bolt Pattern: This might involve measuring the distance between bolts directly opposite each other for 6 and 8 lug patterns or using specific methods for a 5 lug pattern.

3 Additional Ways to Measure a Trailer Axle

1. How to Measure if You’re Missing a Axle Hub or if Axle is Bent

Measuring a trailer axle, especially when you’re missing an axle hub or dealing with a bent axle, can seem challenging, but there are indeed ways to approximate or calculate the necessary dimensions for replacement or repair. Spring Center + Overhang method is one approach, assuming you have a way to accurately measure the spring center and the overhang. See the breakdown and diagram below:

• Spring Center: This is the distance between the centers of the two spring mounts on the axle. It’s a crucial measurement because it determines where the axle will sit in relation to the trailer’s frame.
• Overhang: The overhang is the distance from the spring center to the end of the axle where the hub is located. This measurement is needed on one side, and then you multiply by 2 to account for both sides of the axle.
• Calculation: Adding the spring center measurement to twice the overhang gives you the hub face measurement. The hub face is the total width of the axle from one hub’s flat face (where the wheel mounts) to the other. (Spring Center + Overhang x 2 = Hubface)