Trailer wheel Offset

When purchasing trailer wheels there are a few important dimensions you will need to know. One of these is the ‘offset’. This is the measurement from the centre line of the wheel to the face that bolts to the hub.

For example, if your trailer requires a wheel with an offset and you fit a centre nave wheel (offset = 0), it can cause the tyre rub on the side of the trailer.

On larger trailers the wrong offset can cause problems with the wheel bearings. When a hub is designed the bearings are positioned to accept a centred load. By this I mean the bearings in each wheel are in such a position that they distribute an even load between all of the bearings on an axle. If the wheel offset is incorrect this can upset this balance and cause uneven ware in the wheel bearings.

Some wheels have the offset marked on them. If you read the text on the rim you should see the letters ET followed by a number, this number is the offset distance in millimetres.

If there is no marking this can be worked out quite easily.

There are two ways to work out your offset for your wheel.
Method 1
(B-A)/2

This is the measurement from the rear of the rim to the hub face minus the measurement from the front of the rim to the hub face divided by 2.

100-40 = 60 /2 =30mm.
Method 2

Measure the total width of your wheel, on the image above this is 140mm (40+100 or A+B).

Divide this by 2 which gives 70mm, then subtract the measurement from the front of the rim to the hub face (40mm).

On the wheel shown above this would come to 30mm.
Related articles:
Wheel Measurements
Working Out Your PCD
Tyre Speed Ratings
Trailer Tyre Load Index

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