Wheel Dimensions Definition Guide

We created this wheel dimensions definition guide to shed some light on some of the common terminology used. It is our opinion that an educated customer is a happy customer, and customer satisfaction is our top priority.

Whether you’re in the process of replacing your vehicle’s OEM alloy wheels, or you’re looking to pick up a spare set of steel wheels for the winter, if you don’t know the correct terminology you may end up ordering a wheel that doesn’t properly fit your vehicle. Ordering the wrong wheel product can cost you time and money. If your vehicle is not drivable while you wait for your replacement wheel, this will only add to your headache.

Car Wheel Dimensions and Terminology

• • Bolts / Lug Nuts
    Wheels are mounted to the wheel hub (attached to the vehicle) by a number of bolts that are also referred to as lug nuts. Most automotive wheel hubs have either four, five, six or eight lug holes. Your replacement wheel must have the same amount of lug holes as the wheel hub on the vehicle in question. For example, a 5-bolt wheel will not mount properly on an 6-bolt wheel hub.

• Pitch Circle
  The imaginary circle that passes through the center of each mounting hole on the wheel.

• Pitch Circle Diameter
  The diameter, usually in millimeters or inches, of the Pitch Circle. Also referred to as PCD.

• PCD Notation
  A type of notation (pitch circle diameter notation) used in automotive industries to convey two pieces of pertinent information: The quantity of bolts and the pitch circle diameter. For example, PCD notation of 5x120mm indicates there are 5 bolts, with a pitch circle diameter of 120 millimeters.

• • Bolt Pattern
    Your vehicle’s bolt pattern is essentially the same as PCD Notation. a See our article on how to determine your bolt pattern for more information.

• Hub Centric
  A hub centric axle/wheel will need to be centered before tightening the lug bolts

• Lug Centric
  A lug centric axle/wheel can be tightened during the tightening of the lug bolts.

• Offset
  The distance measured in between the wheel hub mounting surface to the centerline of the wheel is known as the wheel offset, measured in millimeters. This value can be either positive, negative, or zero. When you increase the offset, you actually decrease the space available between the wheel and the suspension system.

• Wheel Size
  If you hear somebody say they’re looking for a 15 inch wheel, they are referring to the height (diameter) of the rim. Wheel sizes can also expressed in this way: Width X Diameter. A 7×14 wheel would have a width of 7 inches and a diameter of 14 inches.

While it can be helpful to know these terms, if you are simply replacing a damaged factory wheel with an identical OEM product, you can expect the rim to fit your vehicle perfectly, so long as it is a genuine OEM wheel that was designed for vehicle, assuming you have not made any aftermarket changes to your vehicle’s suspension system, etc.

Car Tire Dimensions and Terminology

If replacing your wheel with an identical OEM replacement,  you can assume your existing tires will transfer to the new wheel just fine. However, if you plan on buying replacement wheels and tires at the same time, you may need a refresher on some car tire dimension terminology.

• Tire type / metric
  This indicates the type of use the tire was designed for. There are one or two letter abbreviations used for the different metrics: P for passenger, LT for light truck, AT for all-terrain, etc.
• Tire width
  The distance measured, in millimeters, from sidewall to sidewall of the tire.
• Construction
  Refers to the type of construction used to make the tire. Examples include R for radial or B for Bias.
• Aspect Ratio
  The ratio of the height of the tire to its width. An aspect ratio example would be 55, meaning the height is equal to 55 percent of the width of the tire. This value affects handling and performance.
• Rim Diameter
  Essentially the height of the rim section of the wheel, this is a measurement of the diameter of your rim
• Speed Rating
  A tire’s speed rating indicates the maximum speed the tire can handle. This is simply a metric, not an encouragement to speed! Values for speed rating are usually one letter, A-Z with Z being the fastest. When buying tires, make sure to research how the tire manufacturer you choose typically comes up with their speed rating system.
• Load Index
  A measurement of the maximum weight, in pounds, that the tire can support.

Order OEM Wheel Products from Blackburn and skip the hassle!

Of course, the easiest way to guarantee you will be ordering an identical factory wheel is to give us a call at 1-800-981-8321.  Have your vehicle’s year, make, and model ready and we will be more than happy to tell you exactly which of our OEM wheel products will fit your vehicle. In many cases we can ship out your replacement wheel or even OEM hubcaps that very same day.