Wheel Tech: Basics of Tire and Wheel Fitment
*NOTE: This article was originally posted on NICOclub.com, the premier Nissan/Infiniti online user forums.
|The bolt pattern or bolt circle is an imaginary circular diameter formed by the centers of the wheel lugs. Nissan and Infiniti vehicles come with bolt patterns utilizing 4, 5, or 6 lug holes and they are relatively standardized. When looking to change the factory rims on your vehicle you will be asked what bolt pattern is utilized as not all automakers use the same patterns as your vehicle. As an example,the factory 4-lug 240sx bolt pattern is 4 x 114.3 whereas some|
The center bore relates to the size of the hole in the center of the rim. When purchasing aftermarket rims, it is wise to ensure the center bore is the same diameter as that of the hub, this is termed as being hub-centric and ensures the rim is perfectly centered.If the center bore is larger, you should purchase a hub-ring in order to ensure the rim is properly centered and hub-centric. Not utilizing a hub-ring means you are lug-centric and solely utilizing the lugs to center the wheels instead of the lugs and the hub. NOTE: The Center Bore for most Nissan Vehicles is 66.1
|Backspacing is the distance from the inside bolting surface (Hub mounting pad) of the rim to the outer edge of the inboard side of the rim. To determine backspacing simply lay the wheel face down and lay a straight edge (or board, or anything else that is flat) across the wheel. Use a tape measurer or ruler and measure the distance from the bottom of the straight edge to the hub mounting pad. This is your backspace and when choosing rims can help you determine rim depth in the wheel well.|
Offset is the distance from a wheels hub mounting surface to the center line of the wheel. There are three types of offset:
*-- Zero: The hub mounting surface is even with the center line of the rim.
*-- Positive: The hub mounting surface is more towards the front and generally the style wheel used with FWD vehicles.
*-- Negative: The hub mounting surface is toward the back side of the wheel’s center line.
When considering new wheels, offset can make or break a decision. Using a rim with less offset can cause the tire/rim to rub the outer fender and using a rim with more offset can cause the tire/rim to rub the inner fender or even suspension components. As an example, consider the image to the left.
In the example, the factory rim utilizes a +45mm offset (the hub is +45mm from the center of the wheel) and the rim is centered within the wheel well.
Should new rims with a +30mm offset be utilized (the hub is +30mm from the center of the wheel), the edge of the rim is shifted further outbound by 15mm and closer to the fender lip. In some situations, this could cause the tire to rub the fender lip and in extreme cases can cause damage to the tire or fender itself.When utilizing a lowered suspension, there may be a greater chance of this issue.
|Some vehicle designs give the factory wheels a “sunk-in” look. An example of this is the Nissan Maxima, where the rear tires seem further in than the front tires. In order to get the rear tires to be more “flush” with the fender, some enthusiasts utilize wheel spacers. As shown to the left, utilizing wheel spacers can have a similar effect as wheels with a lower offset. It should be noted that utilizing spacers will change the configuration from hub-centric to lug-centric and dependent on how wide the spacer is you may need to get longer (and higher strength) wheel studs.|
A staggered wheel setup is one in which the front wheels are a different diameter or utilize an offset that is dissimilar than the rear. Factory staggered wheel configurations can be found on RWD vehicles but not FWD. A staggered wheel setup on a RWD vehicle is usually utilized to allow the rear to have wider tires for more traction although some enthusiasts use a lower offset in the rear to achieve a more “deep dish” look to the rear wheels. Since FWD vehicles utilize front drive wheels, utilizing a staggered setup would be for looks only.
+1 sizing is when a larger wheel or tire is installed on the vehicle.If the factory rims are 15″ then +1 sizing would be 16″ rims (+2 = 17″, +3 = 18″, etc).Realize that utilizing +1 sizing you should consult the tire shop in order to use the proper sized tire to keep the speedometer as close to factory calibration as possible.
Online Tire Calculators
For those who want to play around with rim and tire sizes to see the effect of changes I suggest utilizing the Miata.net Tire Size Calculator. By simply plugging in the stock tire size vs. new tire size, this calculator will show the differences of the sidewalls, radius, diameter, circumference and Revolutions per mile. To fully put the information into perspective it will also calculate speedometer differences, at 60mph, between the two tires. Quite a useful tool.
Article originally posted on NICOclub.com by: Matthew Moody