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A Guide to Wheel Sizes: Everything to Know About Your Wheels

Have you ever wanted to replace your wheels?  Was it a bit confusing to work out the technicalities and did it take too much of your time to search all that stuff? But in the end that was too difficult for you and you stopped researching it further.

There is a lot to know about wheel sizes and it’s quite complicated to understand all the different concepts related to it. You will learn more about offset, how a wheel’s diameter/width is measured, bolt patterns, and center bore in this blog. This blog post will take you step by step to understand all the minute details related to wheel sizes.

Wheels Sizes Explained

Many drivers spend a lot of money to modify their wheels but they pay very little attention to the compatibility and fitment of the wheels on their vehicle. A bad fitment of wheels leads to many complications and can put your safety at risk.

To know what wheel size will be best for your vehicle, it’s important to understand its different parameters.

A wheel size includes several parameters namely: diameter, width, and offset. For example, one of the rim sizes that the BMW i4 2022 provides is 7.5 x 17 ET30. This wheel has 17 inches diameter, 7.5 inches of width, and a positive offset of 30 mm. The wheel’s size is written on the sidewall.

How to Measure the Diameter of a Wheel?

The diameter of a wheel is measured in inches and it only includes the diameter of the rim and not the tires as well. There are two types of diameters, one is the actual diameter and the other is the overall diameter of the wheel.

The actual diameter of a wheel refers to the diameter which is measured from the surface where the tire is mounted i.e. bead to bead, whereas the overall diameter is measured from lip to lip of the wheel but we only need the actual diameter.

In general, the diameter of daily commuter cars’ or regular cars’ wheels is between 14-19 inches whereas sporty and other luxurious cars fall in the larger sizes diameters.

What Is the Width of a Wheel?

The width of a wheel is measured from bead to bead (from the inside of one bead seat to the other). A bead is a flat area inside the flange of a wheel where the edges of the tire fit onto the wheel. Overall Width of the wheel from the edges of the rim is not the same as the actual width of a wheel from bead seats. We are only interested in the width between the bead seats i.e. actual width as that’s the area where the tire is mounted to.

Width is measured in inches. Most common widths are in the range of 6-14 inches. The wheels’ width is one of the factors that will determine the tire sizes that will fit your wheel.

Wheel Offset Explained

The distance from the center of the wheel to the mounting surface is the offset of the wheel. It is expressed by a value called ET (it’s the abbreviation of the German word “einpresstiefe” with a literal meaning of “press-in depth”).

An offset can be positive, negative, or zero. In the case of the centerline moved towards the vehicle results in a positive offset and if the centerline is moved away from the vehicle you get a negative offset, whereas a zero offset is the centerline. Offset values will define how much your wheels will stick out. It’s important to stay close to the original offset measurements to ensure the correct fitment of the wheels.

What’s the Center Bore of a Wheel? 

The center bore is a hole in the center of a wheel that’s made to fit the hub of the vehicle and it’s measured in nm. It’s generally covered by a cap. When installing a wheel, it’s important to fit the center bore of the wheel perfectly onto the hub of the vehicle. A centering ring can be used to allow one type of wheel to fit many different hub sizes.

When choosing a wheel, it’s of great importance to buy a wheel that has a center bore with either a larger or the same size as the hub of your vehicle. If a wheel isn’t properly centered on the hub of a vehicle it can result in vibrations.

How to Measure the Bolt Pattern of a Wheel?

The bolt pattern includes the number of holes and spacing of the lug holes openings that will align perfectly with the studs of the vehicle’s hub. The bolt pattern includes two numbers, one is the number of lug holes and the other is the diameter of the bolt hole circle. E.g. 5×112 PCD means 5 lug holes with a 112mm diameter of the bolt circle ( it’s the diameter of an imaginary circle that passes through the center of the bolts and it’s called a bolt circle).

The most common lug patterns are 4, 5, 6, or 8. A 4 lug pattern is measured from the center of one lug hole to the opposite one and the 6 lug pattern is also measured in the same way. The 5 lug pattern is measured from the outside of one wheel stud hole to the center of the opposite.

Wrap-up

To buy the right-sized wheels for your vehicle, it’s important to understand what all its different parameters mean and you should stay within the manufacturer’s specified sizes to ensure the correct fitment of the wheel. The exact fitment is very crucial to the quality of the ride and it shall never be overlooked.

At Wheelshome, we provide customized wheels and make our best efforts to satisfy our customers. If you have any queries related to buying wheels, get in touch.

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