With wheels being categorized by numerous measurements, such as bolt pattern, diameter, and backspacing, making sense of what wheels you should buy for your specific vehicle can be troublesome. 

Another one of these measurements is the wheel offset. If you are unsure what offset means, or why it even matters, read along. In this article, you can find out everything about wheel offset you should know when shopping for new rims.

What Exactly Is Wheel Offset, and How Is It Measured?

Wheel offset is simply a measure of the distance from the center line of the wheel to its mounting hub. In other words, how far from the center of the wheel is the area that sits in contact with the wheel hub. It is most frequently measured in millimeters. 

Three basing categorizations of the offset are negative, neutral, and positive. Neutral, or zero offset would mean that the mounting face is in the exact center of the wheel. A positive offset is when the mounting face is moved outwards from the wheel, thus offsetting it towards the outside of the wheel arch. 

On the other hand, the negative offset positions the mounting face “deeper” into the wheel. The positive wheel offset is the most common on today’s cars. Negative offset is usually only seen on aftermarket rims and modified cars.

When shopping for new wheels, the offset is measured with the ET number. ET originally comes from the German word einpresstiefe, which means insertion depth, and as previously mentioned, it is measured in mm. For example, ET0 is an equivalent of a neutral offset, while ET30 would be a measurement for a wheel with a positive offset. More specifically that the contact area of the wheel is offset by 30 millimeters from the center of the rim, and towards the outer side of it.  

How to Find the Right Wheel Offset for Your Car?

Each car typically has a range of ET numbers that are suitable for it. If you need to find the correct wheel dimensions for your wheels, including the ET, you should first check the stickers that are on the inside frame of the driver’s door. If not found there, you should be able to find it in the car’s manual.

When you want to find the ET of your current wheels, it is usually stamped on the inside of the wheels themselves, so all you have to do is look at the back of the wheel. The ET number will be either on one of the spokes or on the mounting hub.

Measuring the Insertion Depth on Your Own

If you cannot find the wheel measurements, it is also possible to measure the offset on your own, although the process is not as convenient. To measure it, you will first need to know the width of the wheel. 

Then, you have to find the center line of the wheel, which will be equal to one half of the wheel’s width. Next, you measure the length between the back edge of the wheel and the mounting hub. 

At this point, you have all the necessary measurements to take the distance of the center line from the length between the back edge of the wheel and its mounting hub. This gives you the ET or the offset of your rims.

Implications of Wheel Offset

If you are looking for wheels for your daily driver, the wheel offset is not that important as long as it falls within the manufacturer’s specified range. However, in sports cars, the wheel offset can have a significant effect on how the car handles.

In any case, wheels with too negative of an offset may cause your tires to rub against the fenders. This will cause damage not only to the fender but also destroy the tires. The negative offset will also result in more rocks being thrown from the wheels onto the body panels, causing chips in the paint and making your car dirtier faster.

On the other hand, an offset too positive may result in the wheels interfering with the internal suspension components, as the wheels will be pushed too far inside the wheel wells. This puts excess strain on the hub bearings, as well as the suspension springs and shocks. Both overly positive and overly negative offsets will also hinder the looks of the car and will make its stance look quite silly.

With too drastic wheel offsets, you may start to experience changes in the handling of your car since you’re changing suspension geometry. In particular decreased stability at higher speeds and unpredictable behavior in corners. Again, this won’t be an issue if you stay within the manufacturer’s specified ET range. If you are looking to adjust the handling of your sports car, changing the ET of your rims may be a viable option but doing so requires more in-depth knowledge.

Remember that the wheel offset, as stated previously, has a significant impact on looks. It is what makes or breaks the car’s design. Of course, the overall design of the wheel, its color, the number of spokes, and its shape is what majorly impacts the look of a car. With that said, the offset is just as important in terms of making your car look good, but this fact is not as apparent at the first glance. 

For this reason, the wheels’ design is often the only aspect people consider when shopping for new wheels. Remember that you should pay as much attention to the wheels’ offset as to their design.

Changing the Wheel Offset Without Changing the Wheels

If you want to adjust the insertion depth of your wheels but do not want to change them, you can use wheel spacers instead. The spacers are used to reduce positive offset, as they decrease the distance between the hub and the wheel’s center. 

The larger the spacers, the more outwards will the wheels be offset. If done correctly, this can improve the look and stance of your car by making it more aggressive because today’s manufacturers tend to bury the wheels inside the wheel arches.

It needs to be understood that adding spacers to wheels will result in the bolts not threading fully in. To accommodate this, you should replace the studs with longer ones when adding wheel spacers.

Difference Between Backspacing and Offset

You may have also heard about the backspacing of wheels. This idea is similar to wheel offset, but the two measurements are not identical, contrary to what many people believe. In short, backspacing measures the distance between the inner edge of the wheel and the wheel’s area that is in contact with the hub. It is essentially the space in the back of the rim, and it combines the measurement of the wheel offset and the width of the wheel.

In terms of effect, the same rules apply to backspacing and offset. Too large offsets result in clearance issues with the suspension and put excessive strain on the internal components. 

Go to the opposite extreme, and tires may rub against the fender, worsen the car’s handling, and increase the turning radius, making the car more difficult to maneuver in tight spaces. These are only a few issues that incorrect fitment could cause.

Wheel Offset Is a Straightforward Measurement

Right now, you should know precisely what wheel offset means. While there are numerous other wheel measurements that determine which rims are suitable for your specific make and model, the ET number is probably the one that people fail to understand the most often. 

However, wheel offset is actually a straightforward measurement and easy to understand. The only scenario in which a more in-depth understanding of the ET is needed is when you are selecting rims for use on the track. In these use cases, the offset can impact the handling on the limit. In all other cases, it’s always best to stick to the ET recommended by the manufacturer.to stick