How to Measure Rim and Tyre Backspace
Measuring the backspace for a trailer wheel, also known as the wheel offset, is an important step when selecting wheels and tires to ensure proper fitment. The backspace refers to the distance between the mounting surface of the wheel and the back edge of the wheel.
Here’s how you can measure the backspace for trailer wheels:
- Straightedge or ruler
- Measuring tape
- A flat, level surface
- Choose the Wheel: Select the wheel you want to measure the backspace for.
- Locate the Mounting Surface: Find the mounting surface of the wheel. This is the side of the wheel that will attach to the trailer hub. It is typically the flat surface behind the wheel’s spokes.
- Measure the Total Wheel Width: Using your measuring tape, measure the total width of the wheel from one edge to the other. This measurement should include the entire width of the wheel.
- Measure the Distance from the Mounting Surface to the Back Edge: Place a straightedge or ruler against the mounting surface of the wheel. Measure from this mounting surface to the back edge of the wheel. This distance is your backspace.
- Record the Measurement: Write down the backspace measurement you obtained.
It’s important to note that there are two types of wheel offsets: positive and negative.
- Positive Offset: If the mounting surface is closer to the front (outboard) edge of the wheel, it is a positive offset.
- Negative Offset: If the mounting surface is closer to the back (inboard) edge of the wheel, it is a negative offset.
Video demonstration is as below.
When selecting trailer wheels and tires, you’ll need to consider the recommended backspace or offset for your specific trailer’s axle and suspension setup. This ensures that the wheels and tires do not interfere with the trailer’s frame, suspension components, or fenders.
If you’re unsure about the appropriate backspace for your trailer wheels, it’s a good idea to consult the trailer manufacturer’s specifications or seek advice from a professional in the automotive or trailer industry. Incorrect wheel fitment can lead to handling issues, tire wear problems, and potential safety hazards.