A common mistake when measuring out lip / inner barrel size is that many people would measure from edge to edge as opposed to bead to bead. This is incorrect. Please be sure to start from the tire bead area to the other tire bead.
To do this correctly, please make sure to go from the start of the bead to the other side of the bead. The sample shown below indicates an 9.0" wheel. Since the diameter is 18", this makes the overall wheel 18x9.0".
Now let's look at the outer lip. Once again, start from the bead of the lip area, then stop at where the silicone sits. Measurement below turns out to be 2.5", so this is an 18x2.5" Outer Lip.
To measure the inner barrel, the same principle applies. Go from the silicone to the inner barrel side of the bead. Sample below shows a 6.5", so this is an 18x6.5" inner barrel.
Another common mistake is to measure the from the "inside" of the wheel" as shown as shown below. This is also incorrect, as you will not always get a precise measurement.
You will not get a precise measurement if the tire is still on the wheel. So please be sure to have your local tire shop dismount your tires prior to measuring.
Certain wheels such as the Work Equip 05, Rezax, etc. is sandwich mount, so please remember to account for the 0.5" thickness in between the outer lip and inner barrel. Also, certain wheels such as SSR come in 1⁄4 increments, so your outer lip/inner barrel would come out to be something such as 2.75" as opposed to 3.0" or 2.5". Please make sure to measure accurately!
If you are still unsure or are having trouble, we can perform these measurements for you if the wheels are brought in to us (via appointment walk-ins or shipped to us)