Beyond offset: navigating the differences between OE and aftermarket wheels.
So, you found a new set of aftermarket wheels that seem to tick all the boxes. The configurator shows the wheels are correct for your car, the design is just what you had in mind, you like the color, and the price is right.
But then you notice that the offset is slightly different to your existing wheels. The wheel width might also be different. Additionally, the aftermarket wheelset might be offered in a square configuration whereas your factory wheels are staggered.
What do these differences mean? Will the wheels fit your car or will they damage it?
Often, people on the market for aftermarket wheels are put off by these differences and decide against the purchase. In certain circumstances, e.g. with older cars where the factory wheels are no longer available, this reluctance will have negative consequences down the line. Rather than replacing the old and worn-out wheels with a new set that will last for decades, some drivers will revert to repeatedly welding cracked rims, or sourcing second-hand wheels of ambiguous quality from marketplaces like eBay.
The most important thing to understand when considering the discrepancies between OE and aftermarket wheels is that there is a range of offset and width parameters that will fit any car. There is nothing immutable about the factory specifications.
Let’s address each potential difference – offset, width, and configuration – and understand their implications.
Offset: The offset (“ET”) is measured in millimetres and describes how far the wheel’s mounting surface sits from its centreline. In a nutshell, lower offsets make the wheel protrude further out. Higher offsets, on the other hand, will have the wheels more recessed within the wheel arches.
For example, let’s say your factory wheels are offset 40 while the aftermarket ones you are considering are offset 37. This means that the aftermarket wheels will sit 3mm closer to the wheelarches. To put this in context, 3mm is the roughly the width of the dental tape you clean your teeth with. Obviously, such a small difference is neither here nor there and will cause no issues to your car. Often aftermarket offsets can differ by as much as 10 or even 15mm without issue.
They key idea here is that there will always be a range of offsets around the factory offset that will work. This is because there is always wiggle room inside your wheel arches regarding the positioning of the wheel. And as long as the offset falls within a safe range for your car, it shouldn’t cause any issues. In fact, adjusting the offset slightly can often improve the aesthetics of the vehicle.
Width: In the wheels’ description, this will be the number that is typically followed by a “J” and it is measured in inches. For example, an 8J wheel will be 8 inches wide.
Wheel width determines tire fitment. A wider rim can accommodate wider tires, which may provide better grip and handling, especially in performance applications. Conversely, a narrower wheel might be preferable for a more conservative or everyday fitment. Narrower rims are often also preferable in winter conditions, as the narrower tyre allows the car to better slice through ice and snow.
Again, as with offset, for any given wheel diameter there will invariably be a range of compatible widths. Almost all OE fitments will attest to this anyway, as various factory wheels will be offered in a variety of widths (including various tyre widths). As long as the width is within a reasonable range for your vehicle, it should be compatible.
Configuration: Square versus staggered wheel configurations refer to whether all four wheels are the same width (square) or if the rear wheels are wider than the front ones (staggered). Staggered setups are common in performance cars, as they can improve traction and handling by increasing the contact patch of the rear tires.
While there are numerous aftermarket staggered configurations, it is more likely that an aftermarket wheelset will be square. This is simply down to logistics and the fact that aftermarket wheel makers strive to cater to the widest range of vehicles with the smallest array of rims.
Again, this on its own should not discourage you, as a square configuration will work fine for the large majority of passenger cars. Indeed, it can offer more balanced handling characteristics and allow you to rotate wheels, getting the maximum mileage out of your tyres. It will also make life easier when it comes to purchasing new tires.
And by no means does a square configuration mean that your car will not perform as well. For example, AUDI famously equip most of their cars from the factory with square configurations, even for their high-end models like the S8.
In summary
Understanding these differences empowers you to make informed decisions when selecting aftermarket wheels. While deviations from factory specifications may seem daunting at first, they offer an opportunity for customization tailored to your needs and preferences.
Moreover, aftermarket wheels from reputable manufacturers like Ronal or Borbet undergo rigorous testing to ensure there will no problems. Entire teams of engineers work full-time to ensure the companies’ offerings are correct, and the results of their work are reflected in formal and incredibly detailed technical documents. In short, if a reputable aftermarket company say a given set of rims will fit your particular car, you can take this to the bank. There is zero probability they are wrong.
And best of all? If you have any doubts regarding a fitment, be it OE or aftermarket, our dedicated team of wheels specialists are here to help you. Drop us an email at sales@alloywheelsdirect.com or use the webchat facility on our site to speak to us in real-time.
