Learn how to measure wheels correctly before you decide to buy a new set

Knowing the proper wheel sizes required for your vehicle is critical to the performance and safety of your ride.

Once you know how to measure your wheel size, you’ll prevent yourself from making the mistake of buying wheels based solely on looks.

Many wheels on the market today can be factory made or custom built. Factory wheels are installed on basically all stock vehicles, but they may not be the desired wheels for the owner. Aftermarket custom wheels are very popular in these circumstances, as they satisfy the owner’s vision for beautiful styling that complements their car. Buying the right wheel for your car means buying one that fits and looks good. Each type of wheel has specific measurements that make it right or wrong for the vehicle, whether it’s a car, van, SUV, or truck. As a general rule of thumb, you will always need to measure new wheels to know which ones you are buying.

First, take your standard wheel and lay it flat on the ground with the inner flange facing up. The entry flange is the rim of the wheel that will be facing inward toward the vehicle body when it is attached. For this case you will need to calculate the setback which is measured from the input flange to the center of the hub which is centered on the spindle. You can use a straight, flat plank of wood to lay across the width of the wheel on the input flange, and then take a regular ruler to measure down to the center hub, which is considered the setback of the wheel.

Next, you will need to measure the lug pattern of the axle that the wheel will mount to. These lug nuts will be centered on the axle and will protrude from the axle and wheel they are secured to. Depending on your car, lug nuts come in various patterns of 4, 5, 6, or even sometimes 8 lugs. For even numbered patterns, you can measure from the center of one lug hole to the center of the lug hole that is directly opposite the one being measured. With odd numbered patterns, you can measure from the top of the top lug hole to the center of the lug hole two distances from the starting hole. This particular measurement allows you to purchase the correct lug pattern for a replacement wheel.

Next, you’ll need to measure the centerline of the wheel to determine if the replacement wheel has, or potentially needs, a positive or negative offset. The offset is determined by the location of the center hub relative to the center line. To locate the center line, you will need to measure from the inner flange to the outer flange and then divide by 2. You can do this with a basic straight edge or retractable tape measure. The actual “offset” of the wheel is the setback of the wheel compared to the center line. An illustration of this would be that if the offset were 6 inches and the centerline of the wheel was 7 inches, this would mean the wheel has a negative offset. If the wheel setback was 6 inches and the centerline was also 6 inches, then the offset would be considered positive. Making sure you have the correct offset allows the tires to spin freely within the space provided by the wheel well where the axle, body panels, and frame meet. Improper offset will cause the wheel to rub on the inside or outside of the wheel, or in very bad circumstances, the brake caliper or rotor, which could cause damage and a strange ride.

In the process of figuring out how to measure the wheels on your car, you first need to determine which tire you would like to purchase, as this will go a long way in determining exactly which wheel to fit. Incorrect wheel measurements will result in it not being compatible with your tires, wasting your time and money. Remember that incorrect trimming will result in uneven weight distribution and damage to surrounding components, so heed these tips on how to measure your wheel size.