In my opinion, there are 2 reasons that someone would install wheel spacers on their vehicle. Some aim to improve aesthetics, while others do it because they “have” to. Aesthetically speaking, wheel spacers can get you the desired stance you’re looking for, whether it’s because you’ve slammed your vehicle or if you have a stock set-up and are looking for a meaner look. When wheel spacers are a necessity, it's usually due to an aftermarket wheel's extreme offset resulting in a wheel that appears to be eaten by the wheel well or coming in contact with brake and suspension components. The application of a wheel spacer can push a wheel out to a more desirable offset, as well as improve the look of a car. Whatever your reason for wheel spacers, proper steps should be taken to get the correct size so damage to your car will not occur.
Measuring Wheel Gap
Measuring your wheel gap is important because there is such a thing as too much offset. Too much offset will result in damage to your fender, wheel, tire, or all three. Wheel gap is the amount of space you have between the inner fender lip and the outside edge of your tire or wheel. Everyone’s wheel gap is different even if you have the same exact car; depending on the life of the vehicle someone else’s vehicle may sit lower or higher, their tires could be a different brand, or they might have stretched fitment tires on their wheels. So, while taking someone’s recommendation can guide you in the right direction, always measure first before buying wheel spacers.
There are a few different ways to measure wheel/tire gap. All you need are a few rulers or a ruler and a foot long strip of painters tape/string, and a big washer.
Measuring Wheel Gap
Two Rulers
Taking one ruler in each hand, set one flat against the inner fender lip hanging down as straight as possible. Measure the distance from the tire edge to the hanging ruler. This distance is the amount of room you have till you would have contact. You will want to get a spacer smaller than this number.
Weighted String or Tape
If you find yourself without two rulers, hang a piece of tape or string from the fender. Using a big washer, or something similar, attach it to the end of the string/tape so it hangs straight downwards. Now just measure from the string/tape to the outside edge of the tire and that distance is your wheel gap. Make sure to get a spacer smaller than this number.
The face side of this wheel bearing hub has a protrusion that the wheel rides on
Hub Centricity
* A set of measuring calipers make measuring quick and easy, especially digital ones that go from inch to millimeter.
Many cars these days and especially European vehicles (all BMW’s for that matter) have a hub lip that the wheel rests on. This is where the wheel gets its main support and also locates the wheel in the appropriate spot. The lip typically stands out about 9-10.5mm from the wheel hub. So, when you’re using a wheel spacer that is less than 10mm, you are decreasing the amount of room the wheel has to sit on. (The spacer slips over the lip) This is important to take into account when choosing your wheel spacer because not leaving enough lip for the wheel to sit on will result in vibration and possible damage to the wheel. Turner Motorsports makes a hub extender, it attaches in the same place the dust cap does and adds an extra 10mm for the wheel to rest on. Any spacer above 10mm will have a 10mm lip on the front for the wheel to rest on - this is a slight benefit to going with a bigger spacer. Also be sure to measure the outer diameter of the hub lip and get a wheel spacer that will fit that; too small and it won’t fit, too big and it won’t support the wheel properly.
10mm Spacer Issue
The 10mm spacer is a popular spacer choice, it seems to be the spacer people choose to start with as it's big enough to make a difference but not big enough to cause an issue in most cases. As stated before, most hub lips are almost 11mm tall and if the spacer is only 10mm thick it is physically impossible for it to fit; it will leave a gap between the spacer and the flat surface of the hub. So, the only thing to do is to shave the lip down a few MM so it will fit. A metal file does the trick, it may not be the prettiest but it works.
Extended Wheel Bolts
As everyone knows, the wheel bolt goes through the wheel and threads into the hub, securing the wheel to the vehicle. Now that you’re increasing the distance between the hub and the wheel with a spacer, it is likely your wheel bolts are not long enough. You'll need to get wheel bolts that are long enough to safely secure the wheel to the car. If your bolt only catches on a few threads you risk stripping the threads and losing a wheel while driving. Figuring out what bolt length you need is simple. Take the length of the stock bolt and add the thickness of the wheel spacer. Ex: 1.625” bolt + 10mm spacer (.3937”) = 2.0187”, so I need a 2.00” bolt. If you’re only adding a 5mm spacer you may not need to get new bolts, seeing as 5mm is only .200”, but to ensure safety I always recommend longer wheel bolts.
If you’re thinking of adding wheel spacers, there are a few different companies that provide them. FCPEuro offers H&R spacers, TMS offers H&R and their own wheel spacers, and ECStuning has H&R and their own brand of spacers - all offering a wide selection of bolts.
So, if you are looking to enhance the look of your vehicle in a subtle but satisfying way a set of wheel spacers could be what you’re looking for. Just make sure to do it in a safe way for you and the vehicle.
Fun Fact:
Most BMW’s can fit a 15-20mm wheel spacer because the wheel well is big enough to fit tire chains and bigger winter tires.
About the Author: Tony Robinett
Tony lives in Spokane, Washington and is a 3-D Design Engineer, machinist, and welder. When he's not at work he is designing and fabricating parts for his M3, and other BMWs alike.
