How to Measure a Trailer Axle

Co-authored by wikiHow Staff

Last Updated: October 26, 2019 References

There are two measurements you need to know in order to get a correct replacement for a trailer axle. First, you need to measure the distance between the wheel hubs, which is known as the hub face, track width, or center of tire measurement. Then, you’ll need to take the spring center measurement. With just these two numbers you can easily order or shop for a new axle for your trailer. As long as you can take the spring center measurement, you can calculate the hub face measurement for a broken axle as well.

Method 1

Method 1 of 3:

Getting the Hub Face Measurement

1
Remove the tires and wheels from the trailer axle so you can reach the hubs. Each set of wheels on your trailer has an axle that runs between them on the underside of the trailer. Use a lifting jack, such as a bottle jack, to lift up your trailer’s axle so the wheels are in the air. Use a socket wrench to loosen the nuts that hold the wheels to the hubs and carefully remove them.^{[1]
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- The process for removing the wheels from your trailer is similar to changing a tire on a car.
- A bottle jack is a large type of lifting jack that locks into place underneath your trailer’s main frame so you can safely jack it up to remove the wheels.
- You can measure any axle on your trailer if there are more than 1.
Did You Know? The hub face measurement is also called the track width or center of tire measurement.
2
Hook the end of a tape measure on the outside face of 1 of the trailer hubs. The hubs are the round discs that the wheels attach to (the discs that have the bolts from which you removed the wheels). Hook the metal end of a tape measure over the outside face of the hub (the part that would normally be inside of the wheel).^{[2]
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- If you have someone around that can help you, have them stand at the end of the axle and hold the end of the tape measure securely in place against the outside face of the hub.
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3
Pull the tape measure along the axle to the outside face of the opposite hub. Stand at the opposite hub and slowly pull the tape measure towards you along the axle. Stop when you reach the outside face of the hub and hold the tape measure in place.^{[3]
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- Make sure that the tape measure is running completely straight along the axle and is not twisted or at an angle that will throw off the measurement.
4
Read the number on the tape measure to get the hub face measurement. Look at the number on the tape measure where it reaches the very edge of the outside face of the hub. This number is the hub face measurement.^{[4]
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- This is the first number you need to know to buy a replacement axle. Write it down so you don’t forget it.
- Note that axles are typically measured in inches.

Method 2

Method 2 of 3:

Taking the Spring Center Measurement

1
Hook your tape measure on the outside of 1 of the leaf springs. The leaf springs are the pieces of metal mounted perpendicular to the axle at each end near the hubs (they are attached to the axle with U-shaped bolts). Put the metal hook of your tape measure on the edge of 1 of the springs that is closest to the hub on that end.^{[5]
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- This method works for taking the spring center measurement by yourself. If you have a friend around, you can have them hold the end of the tape measure in the center of the spring instead of hooking it to the outside edge.
Tip: Some trailers have the leaf springs mounted under the axle, while others have the leaf springs mounted on top. Either way, the process for measuring them is the same.
2
Pull the tape measure along the axle to the inside edge of the opposite spring. Stand by the opposite leaf spring and pull the tape measure straight towards you. Stop when it reaches the inside edge of the opposite spring.^{[6]
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- Measuring from the outside edge of 1 spring to the inside edge of the other gives you the same number as measuring from center to center, so it is an easier way to get the spring center measurement by yourself.
- If you’re measuring with the help of a friend, then measure from the center of 1 spring to the center of the other instead.
3
Read the number on the tape measure to get the spring center measurement. Look at the number on the tape measure where it touches the inside of the spring where you are standing. This is your spring center measurement.^{[7]
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- Write down this number. It is the second measurement you need to know to buy the right size of axle for your trailer.
- Remember that axles are usually measured in inches.

Method 3

Method 3 of 3:

Measuring a Broken Axle

1
Take the spring center measurement first. Measure from the center of 1 spring to the center of the other with the help of a friend or measure from the outside edge of 1 to the inside edge of the other if you are by yourself. You will use this number to get the hub face measurement of the broken axle, so write it down.^{[8]
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- For example, let’s say that the measurement you get is 50 in (130 cm). Write this number down to use in the calculation of the hub face measurement.
Tip: You can only measure a broken axle if it's broken on 1 side between the spring and the hub since you need the center spring measurement. If it broke in the middle, between the springs, you will not be able to measure it and will need to use the VIN or part number to replace it.
2
Measure from the center of 1 leaf spring to the outside of the nearest hub. Hold the end of a tape measure in the middle of the spring on the good side of the axle. Pull out the tape measure to the outside face of the good hub and write down the measurement.^{[9]
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- For example, say the distance from the center of the spring to the outside face of the good hub is 8 in (20 cm). You will use this number with the spring center measurement you got earlier to get the hub face measurement of the broken axle.
3
Add the number you got to the spring center measurement twice. Double the number you got for the distance from the center of the leaf spring to the outside face of the hub on the good side (to account for this same measurement on the broken side). Add this number to the spring center measurement and you have the hub face measurement.^{[10]
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- For example, if the spring center measurement was 50 in (130 cm), and the other number you got was 8 in (20 cm), then you would double the last number to get 16 in (41 cm) and add it to the spring center measurement. Your hub face measurement in this case would be 66 in (170 cm). You now have both the numbers you need to get a replacement axle.