Wheel spacers and Offset

Ryan Dong - Writer; Automobile Expertise |

Wheel spacers play an important role. As the wheels could decide the style of a car, 90% of car modification starts from the wheels. However, car configuration varies from vehicle to vehicle, so they come with different wheel sizes and styles. And car modification enthusiasts are also good at Identifying them. They could determining whether the car is a low, mid or high version by the size of its wheels. Wheel adapters extended wheel studs for factory wheels.

The wheel offset is one of the values required for the measurement of the wheel parts. Along with PCD, wheel bore and width, it is one of the core measurements you need to know about. It is essential to fit wheels with the correct offset. In that way, you could make sure that the wheels won’t rub your fenders, brake calipers or suspension components.

What’s offset?

The hub offset is the distance between mounting surface and centerline. The symbol for the offset is ET, the unit of measurement is mm. ET30 means +30mm Offset. The larger the offset is, the more concave the wheel hub is; conversely, the smaller the offset is, the more convex the wheel hub will be. For example, if a car with an ET30 whee hub offset is replaced with an ET50 wheel hub, the new wheel hub will visually appear to be more retracted into the fender than the original wheel. Conversely, a wheel hub with factory lug nuts with existing studs less than an ET10 offset will look more flared than the original wheel hub.

wheel spacers

It doesn't matter if you can’t understand it now, we are sure that you'll have a better sense after reading this KSP article. To understand the concept, we need an unmounted wheel hub:

Firstly, let’s look at the inner side of the hub. The illuminated part we have marked is the mounting surface, i.e. the contact surface between the hub and the wheel.

Next, facing the direction in which the wheels rolling. Drawing an axis along the middle of the wheel tread, this axis is the centre line.

The distance from the mounting surface to the centre line is the offset.

How to know the offset of your car?

wheel spacers

As shown in the above statistics, most of the original cars have offset values in the range of 35-50mm. In fact, when choosing the aftermarket wheels under the premise of retaining the original parts, a modified wheel with a similar offset is sufficient for the installation.

But if you want to get the data perfectly, it is essential to know the offset of wheel hub.

In most cases, the offset values are engraved on the back of the wheel. They could be founded on the wheel mounting surface or the wheel spokes. So just reversing and check them, or ask the merchant directly.

If for some special reason your wheels do not have an ET number, then we will teach you how to get your them quickly. It won't be too difficult for you.

a. Prepare two steel rulers

b. Measure the width of your wheel and divide by two, this is the X.

c. Place the wheel upside down with the inside of the hub facing up. Place one steel ruler across the hub, taking care not to bend the ruler. Hold another steel ruler vertically against the mounting surface and measure the vertical distance from the mounting surface to the other ruler. This is Y.

d. Offset = Y - X

If a positive value is obtained, it is a positive offset wheel; if a negative value is obtained, it is a Negative offset wheel. And If the sum is exactly equal to zero, then it must be a zero offset wheel.

Positive, negative and zero offset

With the above concepts and practical exercises, it is not difficult to understand this section view.

Positive offset: the wheel mounting surface is closer to the outside of the body with the centre line as a divider.

Zero offset: wheel mounting surface coincides with the centreline

Negative offset: Wheel mounting surface is closer to the inside of the body with the centreline as the dividing line.

wheel spacers

Why we need to change the offset?

Most racing cars choose to widen their wheel track and use wider wheels, cause these methods could increase the cornering speed and high speed stability.

A wheel with a smaller or negative offset will give you more wheelbase directly.

But in contrast, a wider wheelbase will weaken the feedback from the road. This means that although the car has more grip, you will have a weaker feel for how the car is driving. Of course this is only for racing cars, cause we don't have to constantly think about losing control of the car in daliy driving.

Although we are not professional riders, we all have our own quest for stance. The wide body kit was created to match the larger, wider, loss of fender-wrapped wheels.

Similarly, for off-road vehicles, negative offset rims could push the wheels outwards, giving the vehicle better grip. But here we need to take into account the effect of the larger wheelbase on the vehicle's traffic ability.

Reducing the offset will give the vehicle a perfect stance. Nowadays, people are actually looking for a better stance when they go for the offset.

In short, whether it is a car or an off-road vehicle, a more pronounced wheel makes the vehicle fuller and better looking.

The effects of too large or too small an ET value

At this point, you should understand that there is no absolute concept of the size of this value, it is defined based on the different vehicles.

Please add track width to a vehicle to prevent from tire rubbing, similar to a wheel adapter, which takes one-wheel bolt pattern.

We provide a large selection of wheel spacers for various widths and in all bolt patterns,

The ET value is too small:

a. An excessively convex wheelbase may rub against the fender, which will require you to modify the fender with a special fender tool.

b. It will amplify the leverage, resulting in greater forces on the axle components. However, there is no need to worry about leverage changes in the bearings for deflections of up to 50mm (this does not mean you can reduce the deflection by 50mm at all you want), including deformations in the whole suspension system due to leverage changes. Unless you are driving a race car, there is no need to worry about them.

But if your vehicle's suspension is suffering from wear itself, a larger wheel track will make them wear even faster, which will shorten the life of the axle. At the same time, any bumps in the road will be amplified by the steering wheel.

It is important to know that any installation problems caused by too small an ET value can be difficult to solve. So before you buy a wheel, make sure that you know the information which is relevant to your vehicle.

Excessive ET values:

An excessive ET value will directly affect the wheel bay and may cause friction between calipers, shocks, and suspension.

 The clearance between the wheel and the caliper is too small

Contact with a spinning wheel at high speed would be devastating to any component. And you definitely don't want to see your new wheel flying out while you're driving.

 But is there a way to remedy the situation if you bought a custom wheels with bolt pattern with an oversized ET value by mistake? Do you have to leave it at home? No! What you need is a wheel spacer.

How wheel spacers change offsets

Wheel Spacers such as hub centric wheel spacers or wheel adapters hub centric rings stock will separate the hub and the wheel, leaving enough space for your wheel wells and calipers. This will solve the friction problem of the hub caused by large ET value. In fact, this is equivalent to reducing your offset, and a set of high-quality wheel spacers will bring you all the benefits of reducing the offset above.

Most Important, they will save you thousands of dollars on a new set of wheels!


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