Understanding Wheel and Rim Backspacing and Offset

When purchasing new trailer wheels it is important to not only know the required stud pattern but also the offset that will suit your setup.

If wheels with incorrect offset are fitted, you are at risk of the tyres rubbing on the guard or the frame of your trailer, resulting in tyre damage, dangerous driving conditions, and potentially affecting your trailer's roadworthy certification.

Most wheel manufacturers will include backspacing and/or the offset in the product description, however if they dont there are a few ways to figure it out.

The easiest way to begin this process is to measure your wheel "Backspace"

This measurement can be made by placing the wheel on the ground (face up) and measuring the distance between the mounting surface to the back of the wheel. 

E.G: This rim has a backspace of roughly 90mm or 3.5" inches

Image Trailer Wheel and Rim Measuring Backspace

Once you have an accurate measurement you can use the chart (below) to find your wheels “offset”

We know our example image above has a 5.5" rim width, so using this chart we can see that our Offset is 6

Using your offset measurement in conjunction with your stud pattern ensures you get the correct wheels for your trailer.