Wheel fitment on a vehicle can be divided into two broad categories: hub-centric fit and lug-centric fit. Either type of fitment can be satisfactory, depending on the owner’s criteria and preferences, but it is important to understand the difference so that wheel installation is handled correctly. Below is more information about hub-centric and lug-centric fitments.
What Is a Hub-Centric Fitment?
When a wheel is mounted on a vehicle, it is slipped over the axle hub assembly and mounted to a round plate fitted with stud bolts. The wheel contains a central hole, known as a center bore, as well as several smaller openings evenly spaced around the center bore. These smaller openings are arranged in a pattern that matches the stud bolts, and lug nuts are used to secure the wheel to the mounting plate.
For a wheel to be mounted on a vehicle using a hub-centric fit, the center bore of the wheel must exactly match the hub to which it is mated. Factory-installed wheels are almost always manufactured to precisely fit the hubs of their matching vehicles. That level of precision ensures that wheels will be mounted in a hub-centric fit.
What Is a Lug-Centric Fitment?
In many situations, a wheel does not precisely fit a given make and model of a vehicle, leaving some room between the inside of the centerbore and the hub. This is common with aftermarket wheels, which are often designed to be used on a wide variety of makes and models.
Since a wheel with a center bore that is too small won’t fit on vehicles with a larger hub, the preference among aftermarket wheel manufacturers is to make center bores wider than necessary for most vehicles. This prevents expensive retooling in an effort to match the hubs of every potential make and model and still ensures the wheel fits over the hub of most vehicles.
However, if a wheel’s center bore doesn’t fit the hub precisely, as it would in a hub-centric fitment, the wheel must be firmly supported by alternative means. In this case, that means the lug nuts will restrain the wheel against the mounting plate and will keep the wheel perfectly centered around the hub to prevent undesirable handling.
Installing a wheel using a lug-centric fitment requires the vehicle to be elevated prior to the start of the work. This will ensure the wheels will not be pushed off center by the weight of the vehicle during installation. Self-centering lug nuts, which are conically shaped, can help overcome this tendency, but they should be used only to aid in the process, not serve as a replacement for elevating the vehicle.
Which Type Is Better?
The closer the match between the center bore and the hub size, the more precise the fit will be and the less likely other problems are to occur as a result. For example, all things being equal, a wheel mounted using a hub-centric fit is going to be subject to less vibration due to its precision fit. In addition, a wheel that relies on the strength of only its lug nuts may experience stresses that lead to problems such as bent or even sheared stud bolts.
However, since many top-notch wheels, many of which are manufactured to higher standards than factory wheels, are often designed for lug-centric fitment, an effective compromise can be used to ensure a strong fit.
This compromise consists of using hub-centric rings, which are metal or plastic spacers designed to bridge the gap. As such, the potential for wheel vibration and stress disappears when the space between a center bore and hub is eliminated. The practical result is a fitment that meets the strength and stability threshold of that found in a hub-centric fit.
If you are planning to purchase new wheels for your vehicle, then it is important to get assistance from a knowledgeable wheel installer and seller. They can provide information about which wheels are recommended for your particular make and model and perform an expert installation that will allow you to fully enjoy your new purchase.
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