Offset The offset of a custom wheel is the distance from the mounting surface (or mounting pad) of the wheel to the true center-line of the wheel. A positive (high) offset means the mounting surface of the wheel is positioned in front of the true centerline of the wheel. This in effect brings the wheel under the fender well more. Conversely, a negative (low or reversed) offset means the mounting surface of the wheel is behind the true centerline of the wheel. This will cause the wheel to "stick out" from under the vehicle...the "roller-skate" look.
Bolt Patterns Each custom wheel has a different bolt pattern, and some wheels even have 2 different bolt patterns (multi-fit) which allow it to be mounted on a wider range of vehicles. Many vehicles have the same bolt pattern with a similar offset from the factory...but for the most part, it is the vehicle that requires the specific bolt pattern; wheels are NOT universal fit...only multi-fit.
Most Bolt Patterns are represented as follows:4x100 or 4-100 or 4/100
The "4" represents the number of holes in the wheel for the bolts to enter and mount the wheel to the vehicle.
The "100" indicates the diameter of the bolt circle measured in millimeters or inches (in this case millimeters). 4 & 6 bolt wheels are measured from the center of one bolt hole to the center of the bolt hole directly across from starting point. On a 5 bolt wheel, it is not as easy to measure without special BC guage. Again, measuring from the center of one bolt hole, skip one bolt and go to the center of the next bolt hole.
Centerbore
The centerbore of a wheel relates to the center hole in the wheel that centers the wheel on the hub of the vehicle. Most custom wheels today are mass produced and have a large center bore to accommodate many different vehicles. It is recommended that you use a hub-centric ring. Hub -centric rings are hard plastic or metal rings that fit between the centerbore of the wheel and then snugly onto the hub of the vehicle. This centers the wheel perfectly on the hub ensuring that there is no gap when the wheel is installed on to the vehicle. Without hub rings it is possible to get vibrations even if the wheel & tire assembly is perfectly balanced.
Plus Sizing Plus sizing your performance tire and custom wheel package was designed to improve vehicle performance and looks by allowing the fitment of larger diameter rims and lower profile tires. The theory is that while making these changes, you keep the overall tire diameter within 2 or 3% of the original equipment tires. This is extremely important because too large of a variance can cause problems with transmissions…”confusing” the tranny into shifting at the wrong RPMs which can have an adverse effect on fuel mileage. It can also “confuse” sophisticated braking system computers which can lead to more serious problems…like brake failure. Not to mention that it will throw the speedometer out-of-whack. Here's a rule of thumb for "plus sizing": don’t try to figure it out on your own…I have seen several different calculations on the internet and truth-be-told…none are absolutely accurate! Many are close…but tire sizes can vary ever so slightly from one manufacturer to another…so I would trust a professional…and when they are done…simply ask them to show you the overall diameter of the OE tire and the one they want you to buy…the two numbers should be very…very close to being the same! Torque All alloy wheels should be installed using a torque wrench and NOT an air wrench. This ensures that the wheels are not too tight or too loose. Check your vehicle's manual for correct settings, most wheel manufacturers can provide the torque specifications as well. When you install wheels for the first time, you should re-torque wheels after about 25-50 miles. On occasion lug nuts can loosen after a short time; not always, but it does happen because of the heat and the different metals (steel lug nut against aluminum alloy). It is recommended by virtually all wheel manufacturers, and should be insisted on by the installer, to come back in and have the lug nuts re-torqued with a torque wrench. you don't want to simply tighten them yourself...because it can be just as bad to over-tighten them.
