Wheel Sizing 101 | How Classic Wheel Dimensions are Identified
Wheel sizing can be a little confusing, but it's important to know exactly how to measure the dimensions of your wheels, in order to know exactly what tires to purchase, or what wheels to purchase if you plan to replace your current wheels. One of the easiest items to change is the tires and wheels, so it's common for a vintage car to have non-original wheels. This further complicates the situation, as you can no longer refer to original data for tire and wheel fitment. However, you can determine the size of your vehicle's wheels with a few simple steps. Let's get started!
All wheel dimensions are important, but one of the easily confused dimensions is the diameter. For classic cars, it's common to use a 15-inch diameter wheel. The issue that we commonly see is that the customer measures from the outer edges of the wheel, instead of bead-to-bead. This will give you the wrong number every time. To accurately measure wheel diameter, bring the measuring tape just inside the outer edge, where the tire seats against the rim. Coker Tire's selection of steel and aluminum wheels range from 14 to 21 inches in diameter, giving you lots of choices.
Next is wheel width. Again, this one is a bit tricky because you will measure from bead to bead, instead of the overall width. In the case of the wheel pictured, it is advertised as a 7-inch wide wheel, even though the overall width measures approximately 8 inches. That's because the bead-to-bead measurement is 7 inches. Obviously, this measurement is hard to obtain if you still have a tire mounted to your wheel, but you can usually slide a tape measure through a slot or window in the wheel to determine the width. Coker Tire's selection of wheels range from 3 to 14 inches in width, providing fitment for Model A's, '50s classics and custom Pro Street builds.
Backspacing is another important measurement, when it comes to proper fitment in your wheel wells. This is another area where non-original wheels can really mess with the overall look of your car, as the wrong backspacing can pull the wheels too far inward or push them too far outward. Backspacing is measured from the rear of the mounting flange to the inner edge of the rim. You can typically measure this with two measuring tapes or two straight edges, or a combination of both. One measuring tape goes across the rim, resting on the inner edge. Then, the second measuring tape goes from the mounting flange to your first measuring tape. This gives you the backspacing. Common backspacing on classic vehicles ranges from 3 to 4 inches, depending on the application. Later model applications uses more backspacing, giving the front side of the wheel a more flush appearance, where as vintage fitments offer the deep dish look. The term backspacing is often confused with "offset"...the two terms relate to the wheels spacing, but backspacing is more of a vintage term, while offset applies to more modern fitments. All Coker Tire products are measured with backspacing (in inches) instead of offset (in mm).
Finally, we have bolt pattern. On five-lug applications, this is measured from the outer edge of one lug hole to the center of the one furthest away from it. All 4, 6 and 8 lug wheels measure straight across from center to center of the holes. Bolt patterns are typically written 5x4.5 or 5x4-1/2, and some people may say "5 on 4-1/2" when referring to bolt pattern. No matter how you say it or type it, we have the right wheels for your application. We offer most common bolt patterns including 5x4.5, 5x4.75, 5x5, 5x5.5, 6x5.5 and more! Check out our IN DEPTH Bolt Pattern article to learn more.
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