Last Updated on August 2, 2023 by John Robinson
Changing wheel size is often inevitable for stancing or bringing your car or truck to its top performance. It might seem simple at first, but some things can potentially ruin the whole plan of making your car look and work better. One of them is failing to calculate custom wheel offset.
At times figuring out offset can be confusing, so it is best to do a quick research before you try to alter it. Making car modification mistakes is an expensive hobby. Hopefully, this article will help you steer clear of that.
What Is Considered a Normal Offset?
For better or worse, the is no such thing as a standard wheel offset that fits any vehicle. This specification only shows how much clearance the wheel has inside the wheel well and how far the mounting hub is from the wheel centerline. This means that engineers set a specific offset for the car model to make sure the wheels don’t rub against the well or fender while you drive. It also has more practical functions like improving stability and cornering.
Thus, the “normal” offset of your car is the one mentioned in its manual. Be careful with charts. Looking up information using only make and model can give some misleading information. Some specs change from one year and trim level to another, so always pay attention to that if you use outside sources.
Positive vs Negative Offset
The offset can be zero, positive or negative. The difference lies in how far it strays from the zero point. The type of offset is easy to spot visually. Zero offset looks neutral, the hub is aligned with the centerline. It neither protrudes forward nor hides inside the car’s body.
Positive offset pushes the hub out to the street side of the vehicle. It makes the discs appear almost in line with the tires. The wheel itself is mostly hidden inside the well. This offset is often used in trucks to make more room for wider tires. Since the wheel is mostly tucked in, you can safely fit bulkier off-road tires and wheels. The clearance is the only limit here, and even that can be slightly adjusted to accommodate the upgrade. However, the positive offset will give you a headache if you want to stance your car.
And finally, a negative offset is what creates that iconic deep dish look. The mounting hub is located farther from the street side and closer to the car’s body, so the wheels often stick out a little. “This offset is not for everyone. You either hate or love it,” says Oliver Brown, Data Coordinator at Wheelssize.com.
A positive offset is all about compromises. It is perfect for stancing and aesthetics but not that great for versatility. A wider track provides better stability during cornering, but you must sacrifice steering responsiveness.
Does Wrong Offset Affect Anything?
Wheels should be regarded as a vital part of the vehicle. Besides many other functions, they ensure your safety on the road. Any custom offset must be taken seriously, especially if you are going for a negative one. We have already covered that wheel offset can influence handling. But in case you neglect to calculate it properly, the consequences will be more noticeable and expensive.
The first thing that suffers from the wrong offset is usually clearance. If there is not enough space for the wheel to safely turn inside the well, it can rub against its walls or fender. Naturally, it can only lead to damage and chipped paint. This is bad enough, but tire wear is much worse. The rubber can overheat from constant friction and deteriorate faster. In the worst case scenario, a tire can burst where it rubs against the surface.
The body and fenders are just some parts that rely on clearance for protection. Suspension and brakes can rub against the wheel too. And damaging them is even riskier. That is why you should also learn about another measurement associated with offset, the backspacing. It is the distance from the mounting of your wheel to its edge that faces the car body. Positive offset creates more backspacing, hence, it brings the wheel closer to suspension and brakes. And negative offset reduces the backspacing leaving more free space.
Different technics help to adjust the car for a new wheel and avoid this mess. For instance, if the only problem is the fender, it can be replaced or rolled to accommodate wider wheels. And wheel spacers can be a good solution if the wheel gets too close to the body.
How Much Offset Difference Is OK?
There is actually a very simple rule that will help you in most cases. Just remember that changing offset within 5mm is safe. But anything beyond that will require some calculations and careful planning.
Many technicians recommend avoiding increasing positive offset if you can help it. Bringing wheels closer to the brakes, suspension and body is rarely a good idea if you already have a positive offset. Sure, wheel spacers can help, but they are considered a controversial part by some shops.
The spacers themselves are not the problem, but their quality often is. This part is supposed to withstand enormous weight of your car and support the wheel. It effectively become a part of the hub, so the material and its durability become crucial factors. Installation can also present new issues with lug bolts. You will need to use longer bolts to secure the wheel in place, but too much space between the wheel and the hub can put extra strain on them resulting in more unpleasant problems to deal with.
How to Choose a Perfect Offset?
Custom offset is not always about compromises. Unless you want some extreme changes, a good offset for you should be simply a safe one. Regardless of what you want your car to look like, remember to leave (or add) enough space to protect your car’s body and tires.
To make sure you can fit a new set of wheels start with careful calculations of the new offset and backspacing. If you are using special online calculators remember that you must always compare measurements to the OEM offset and size. The 5mm rule will not work if you are already comparing two custom offsets. This can result in misleading and potentially harmful data.
Now that you know about the risks, evaluate your goals again, calculate and consult a professional to get the best upgrade for your wheels.