There are only five dimensions of importance when measuring a wheel: Rim Diameter, Rim Width, Offset, Backspacing and Bolt Circle (PCD).
The diameter of the wheel's bead seat where the tyre sits, NOT the overall diameter of the wheel.
The width of the wheel is measured from bead seat to bead seat, this is not the overall width of the wheel you will need to add approximately 1" for overall width.
Offset and backspacing
The positive or negative distance from the wheel's centre line to the mounting surface of the wheel.
Backspacing is the distance from the mounting surface of the wheel, which contacts the hub, to the back rim flange.
The size of the hole in the back of the wheel that centers the wheel properly on the hub of the car. Many aftermarket wheels will be drilled to a larger universal size, and uses hub rings (spigot rings) to reduce the size to match the hub on the car for perfect centering. Generally speaking, a perfect hub size match and hub rings can be optional for vehicles that use lug nuts, but are absolutely required for vehicles that use bolts such as BMW, Mercedes, and VW and most european vehicles.
Spigot Rings / Hub centric rings
Most aftermarket wheels are manufactured with a center hole that will fit a wide range of vehicles. The hub-centric ring is an installation tool used to help hold the wheel perfectly centered during installation. Use of a hub centric ring can help in reducing minor vibrations. Proper installation and torque sequence is required to correctly center a wheel with or without a hub centric ring.(spigot ring)
Bolt Circle / Stud Pattern (PCD)
Sometimes referred to as bolt pattern or PCD: the number of stud holes on the diameter of the imaginary circle that each stud hole is centered on
Example: 5-4.75 PCD would be a 5 stud wheel and the messurement as in the diagram below for 5 stud would messure 4 3/4" or 120.65mm
5 Stud. Measure from back of hole to centre of the second.
4 Stud. Measure middle two holes directly across from each anther
6 Stud & 8 Stud. Measure same as 4 Stud.
MAINTAINING YOUR WHEELS.
WHEEL CARE TIPS & INSTRUCTIONS FROM AMERICAN RACING WHEELS:
If you are wondering how much time will be required to care for your wheels, the answer has a lot to do with how they are maintained. Your local climate and road maintenance can affect the care required and life span of a wheel finish. For harsher climates, American Racing suggests that you retain your original equipment wheels for optional use as wintertime equipment.
The first rule in caring for any automotive wheels regardless of finish is to keep them clean. Generally speaking, from week to week during your car wash cycle, it’s best to clean them with a soft brush, soap and/or mild degreaser or quality spray-on Wheel Cleaner. For best results, it is important to keep wheels clean, not allowing road film, contaminants and brake dust (which retain moisture) to accumulate and sit on the surface. If you live in a harsh winter climate where salt and chemicals are used during the winter, regular cleaning is even more important. Be careful in selecting wheel cleaning products—select products that are safe for the finish of your wheels. Avoid harsh or abrasive cleaners. Some cleaners are harsh and could damage your wheel finish. Also be aware that many car washes use strong chemicals to clean wheels and tires that could cause damage to your wheel finish or even your automotive paint. NEVER CLEAN HOT WHEELS, allow wheels to cool or cool them with running water. Another important step is to seal your wheels with a sealant that will reduce static and resist brake dust, such as American Racing Wheel Wax.
Protect your investment, clean your wheels regularly.
Your after-market wheels were manufactured in one of four finishes:
a. Chrome (applied to either aluminium alloy or steel).
b. Polished Aluminium Alloy (no protective coating).
c. Clear coated and/or Painted.
Aluminium or steel wheels plated with chrome are beautiful and can significantly change the appearance of your car or truck by attracting light to base areas of your vehicle. If maintained, the chrome finish will produce a brilliant shine. To reflect light, which produces the attractive brilliant finish, the wheels must be cleaned regularly. It’s best to clean them with a soft brush, soap and/or mild degreaser or quality spray-on Wheel Cleaner. Rinse thoroughly. After cleaning your wheels do not allow soap, chemicals or water to sit on the surface and produce water spots—dry your wheels with a soft, non-abrasive towel. As stated above, it is important to keep wheels clean, not allowing road film, contaminants and brake dust (which retain moisture) to accumulate and sit on the surface. If you live in a harsh winter climate where salt and chemicals are used during the winter, regular cleaning is even more important. Periodically, polish chrome wheels with American Racing Chrome-Tech, or some other quality non-abrasive chrome polish. For best results and to reduce cleaning efforts in the future, after polishing and/or cleaning, apply American Racing Wheel Wax to seal the surface—this should help avoid problems in the future and will reduce static so that your wheels are more resistant to brake dust. The products mentioned above are available from stock..
Polished Aluminium Wheels.
Polished aluminium wheels are very popular, particularly with racing, off-road and hot rod enthusiasts, and we sell thousands of them each year, however, they do require more periodic maintenance than other finishes, depending upon the climate, road conditions and your vehicle car care practices in general. Polished aluminium alloy wheels require the highest degree of maintenance and a certain amount of oxidation is to be expected as the wheels naturally oxidize with age. Polished wheels can be re-polished commercially or by hand after many years of use, effectively restoring them to an almost factory original condition. When new, coat your polished wheels with a quality, hand-applied sealant product such as American Racing Wheel Wax. This coating will assist in preventative maintenance by resisting brake dust and other contaminants. When your polished aluminium wheels begin to lose their shine or are dirty with road film or brake dust, begin by cleaning them as instructed above. If you use a brush, be careful to avoid scratching the uncoated, polished aluminium alloy by using only a SOFT brush. Follow up by polishing them by hand with American Racing Metal Polish, or another quality metal or wheel polish. After polishing, coat them with American Racing Wheel Wax according to instructions. If they are in bad condition, this will take some time, and polishing wheels is never an easy task. For faster and perhaps easier results, use the American Racing Air-Compressor Powered Polisher or a Dremmel-type tool mini-polisher, with the correct polishing mini-pads. Just swab on American Racing Metal Polish, then buff them with the polishing tool. Mini power tool polishers will clean up and polish your wheels quickly, saving time and producing a brilliant shine. If your wheels have deeply imbedded brake dust, animal urine or other contaminants from lack of maintenance, you can try an aggressive spray-on wheel cleaner (be careful, some contain acid) with a brush, BUT DO NOT ALLOW IT TO SIT ON THE SURFACE AND ETCH THE POLISH SURFACE. Rinse your wheels thoroughly and dry with soft, non-abrasive cloth. We receive many inquiries about clear coating or chrome plating polished aluminium wheels, as a maintenance option. If you are interested in applying a permanent protective coating to your polished aluminium alloy wheels, you may wish to consider taking the wheels to a local wheel reconditioning or chrome plating firm in your area. This service involves professionally polishing and applying a liquid or powder coat acrylic or polyester clear coat or chrome plating the wheels. Services of this type can be found under "wheel reconditioning" or "chrome plating" in the Yellow Pages or on the worldwide web. Polished wheels look great, but do require regular maintenance.
Clear Coated Wheels.
American Racing manufactures many styles that are permanently coated with a clear protective coating, essentially a non-pigmented, clear paint. The clear coating that we use is the same material that we use for the original equipment wheels we manufacture for leading automobile manufacturers. Your clear-coated wheels should require only soap or a quality Wheel Cleaner product, water and a soft brush. Once you have cleaned your clear coated wheels, a coat of hand-applied American Racing Wheel Wax or a quality, non-carnauba, non-abrasive polymer sealant-quality wax will enhance resistance to brake dust and contaminants. Wheel Wax works well and will save you time in the future.