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What size trailer hub do I need?

What size trailer hub do I need?

The wheel hubs on a trailer enable it to turn with the forward motion of the vehicle that is pulling it. If the bearings in these wheel hubs stop functioning efficiently, the trailer wheels won’t turn properly and could freeze up altogether.

If your trailer wheels aren’t turning smoothly, it’s a sign that you need to replace one or both of the trailer hubs. To do this, you need to know the size of the trailer wheel hub.

Your trailer wheel hub must match the spindle on the axle of your trailer.

The inner and outer bearings should have specific part numbers marked on them. To find these numbers you must first remove the wheel hub from the trailer.

1. Remove the Wheel Hub from the Trailer

First, lift the trailer off the ground using a jack. Put stands under all four corners of the trailer. Loosen the wheel nuts and remove the wheel.

Use a screwdriver to remove the dust cap in the middle of the trailer wheel hub.

Remove the wheel hub bolt and pull the wheel hub assembly off the spindle.

2. Determine the Correct Wheel Hub

Normally, the numbers displayed on the back of a wheel bearing will correspond with the matching spindle size.

These numbers should be on the inner and outer bearings.

If the numbers are not easily readable, the alternative is to measure the trailer wheel hub.

As with vehicle wheel hub assemblies, the trailer wheel hub will have a certain number of lugs, or bolts, arranged around the circumference.

Usually, there will be four, five or six of these lugs. The pitch circle diameter (PCD) is the diameter of an imaginary circle drawn between the lugs.

The PCD of your replacement wheel hub must match this measurement on your old hub. This is how you know you have the right size of replacement hub.

  •  For a four or six-bolt pattern, measure from the middle of one lug to the outside of the opposite lug
  • For a five-bolt pattern, start from the middle of one lug and measure to the outside of the next but one lug.

To get the right figure for your hub size, multiply the diameter measurement by the number of lugs.

3. Measure the Seal Size

You must also make sure that the seal is the correct size on your new trailer wheel hub.

This is crucial because the seal helps to retain grease inside the hub. Again, there should be a number displayed on the seal. If not, measure both the inner and outer diameter of the seal.

Most trailers will use a standard double lip seal. However, some bearings that use oil will use a triple lip seal. Here, you will need to measure all three seal diameters.

4. Order Your New Trailer Wheel Hub

Using these measurements, you can now select the correct size of hub for your trailer.

We stock a comprehensive range of trailer wheel hubs. For more information or advice about replacing your wheel hubs, please contact us.

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