Besides the size, wheel offset and backspacing are both essential specifications for changing wheels. To measure the wheel offset, you will need to remove the wheel, measure the centerline and substruct it from a distance between the mounting point and the edge of the rim. And to measure backspacing, you need to remove the wheel and measure the distance from the mounting spot to the edge of the rim.
All measurements must be made using a precise 90-degree angle. And it is much easier to do with a ruler rather than tape. We will discuss some more practical tips and techniques that will help you measure the wheel's offset and backspacing later because each case is worth going into more detail step by step.
For now, let's make sure we are on the same page since these two measurements are often confused. Wheel offset indicates the space between your wheel's mounting spot and its centerline. This specification can help you determine if a specific wheel is suitable for your vehicle. It also influences the way wheels fit inside the wheel well. A negative offset makes them stand out more, and a positive offset tucks them in closer to the vehicle's center.
While backspacing is the distance from the wheel's mounting surface to the inmost edge of the rim. It depends on the offset and shows how much space the wheel takes inside the car body. This measurement is very important for car enthusiasts who want to upgrade the suspension and braking parts.
How to Measure a Wheel Offset?
The easiest way to find wheel offset is to look it up in your owner's manual or use online calculators and offset charts. However, that option can only work for stock offset and OEM wheels. This step-by-step wheel offset measuring guide will come in handy for other cases.
To measure wheel offset, you will have to:
- Remove the wheel and lay it on the floor face down.
- Put a straight edge on the rim lip.
- Measure the distance with a ruler in millimeters from the floor up to the edge and divide by two to find the centerline measurement.
- Measure the distance from the mounting point up to the edge.
- Substruct the centerline measurement (1/2 of the distance from the floor to the edge resting on the rim) from the distance you got between the mounting point and the edge.
You can throw in an extra step and measure the distance between the floor and the mounting point. Once you get that measurement, substruct it from your centerline measurement. It should give you the same number as in step 5. If there is a discrepancy, you should start over from step two.
There is also an easy way to tell if your wheels have a positive or a negative offset at step 4. If the number you get is higher than the centerline spec, your wheels have a positive offset. And if the number is lower, the offset is negative instead. This is important for the backspacing that we will examine next.
Measuring the custom offset is an essential step if you want to change your wheels or check if the current offset is right for your vehicle. But keep in mind that whenever you decide to alter this specification by getting a different set of wheels, you have to compare it to the stock values, not the current custom offset specifications.
How to Measure Backspacing?
Measuring backspacing is much easier than finding the offset. You only need to take three steps to get the measurements right.
To measure wheel backspacing, you will have to:
- Similarly, take the wheel off and put it on the floor face down.
- Place a straight edge on the rim.
- Measure the distance with a ruler from the mounting to the rim lip.
- In contrast to offset, wheel backspacing is often measured in inches instead of millimeters. You can convert the measurements or use the inch ruler for this purpose.
Another thing you can do with measuring backspacing is to get the numbers without taking the wheel off. If you want to measure backspacing with your wheel still mounted:
- Place a straight edge on the rim lip directly across the middle.
- Trim its edges to fit perfectly on the rim lip without touching the tire.
- Proceed to measure the distance from the edge to the mounting face.
This will take more effort, but on the bright side, you will avoid a lot of work by taking off a wheel and tire only to put them back on again after a minute. But it still can be challenging as it is.
Why Should You Measure Offset on the Wheel?
Every vehicle has a certain offset defined for it at the stage of design. This means it would reach its optimal performance with this stock offset that should guarantee normal handling and clearance inside the space limited by the wheel well and fender. If a set of new wheels throws this careful balance off, then tires, suspension, brakes and car body can get damaged.
The wrong offset can lead to a risky situation when the wheel rubs against the fender or some vital parts. It can also affect steering and handling. And yet custom offset can be beneficial if done right. It enhances the looks and can help with cornering speeds by altering track width.
Why Measuring Backspacing Matters?
Wheel backspacing can be a way to avoid rubbing problems by increasing the distance from the mounting face to the tire even further. By slightly reducing the stock backspacing specifications, you can make the clearance bigger to fit larger performance parts.
However, it is always influenced by the wheel width and offset, so be careful to get both measurements before you make the final choice.
Altering offset and backspacing should not be taken lightly, as you are messing with the mechanical performance of your vehicle. That is why you need to get the measurements right if your car has custom wheels and you plan to change them.
How Spacers Affect Offset?
Spacers can actually reduce the offset and allow you to install larger wheels if the fender leaves enough space for that. Essentially, spacers push the wheels further apart and away from the hub, so the wheels begin to stick out, not unlike with a negative offset. If they are installed correctly, spacers can be a reliable way to customize your wheels and create a fierce look, even if your wheels have a more positive offset.
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