This article was written by ffrpwner, NICOclub’s Z32 Forum Moderator.
Let’s start with the stock wheels. Note this setup is for the Twin Turbo model only, all others use the Front setup all around for all four (4) wheels. I will not explain or mention the spare tire/wheel here at all.
Front: 16” x 7.5” 45mm Offset
Rear: 16” x 8.5” 35mm Offset
The First number represents the Wheel Diameter, the second Number represents the Wheel Width. The Third Number represents the Offset.
The Diameter is the final diameter of the wheel, the distance measured from one point on the external circumference, passing through the center of the wheel, to the opposite point on the circumference. In this case, a total of 16 inches.
The Width is the distance from one side or “face” of the wheel to the other side. You usually refer to it as “how wide are the wheels”. In this case, 7.5 inches for the front and 8.5 inches for the rear.
The Offset (and this is when people go nuts) is the distance between the center and the mounting pad. To explain better, is the distance between the wheel center point (width’s center) and the mounting pad of the wheel (the surface that touches the Brake Rotors on the car that has the five holes for the lugs).
The offset can be Negative, Zero, and Positive. Positive will tell you that the pad is to the outside of the center, Zero means the mounting point is at the center, and Negative means the pad is to the inside of the center (so you get a BIG lip).
To avoid going crazy calculating all this for aftermarket wheels, the first step is to convert all the numbers to one unit. On this case, I prefer to use Millimeters as it is more precise. To convert, multiply inches by 25.4. This means (in case you failed Math in HS) that: 1” = 25.4 mm
When you buy new wheels, you have to determine first what Diameter you want. 17 and 18 is the common for the Z, but you can go higher if you want, just consider that you should keep the final diameter close to the original number (that is, the diameter with the tire).
Then you determine the Width and Offset, and you have to choose both numbers at the same time because they are 100% related to each other and a real good fitment will depend on both of them and not just one.
You should make up your mind on what Width you would like to have, then, find out what Offsets those particular wheels are offered, and then sit down with a calculator and do some math as follow:
Lets take a 17” x 10” 45mm Offset wheel for an example to replace the rear wheels:
– Convert the Width to mm: 10 x 25.4 = 254mm
– Divide it by 2 (to get center point): 254 / 2 = 127mm
– Subtract the offset from it: 127 – 45 = 82mm
Now you have 82mm and that is the distance from the mounting pad to the most outside point of the wheel. Compare it to the stock wheel: 72.95mm. That is about ½ of an inch wider (to the outside only!).
Now subtract the 82mm from the total Width: 254 – 82 = 172mm. This is the distance of from the mounting pad to the most internal point of the wheel. Compare it to the stock wheel: 142.95mm. That is about 1 inch wider (to the inside).
So there you have it, you new wheel is going to stick out ½ inch more than stock, and is going to be 1 inch wider to the inside. Note that those wheels are 1 ½ inches wider than stock, but only ½ inch sticks out, the rest goes to the inside.
Now get under your Z and measure around to see if you have clearance for it or not. If you have a TT, the HICAS will be a problem for 17 inches wheels, so choosing 18 would be better, but in the example above, you could keep 17 if you get a smaller Offset, so the wheel “slides” towards the outside (just like using Spacers). But then you have to consider how much can you get the wheels stick out of the rear fender before if rubs or just looks ridiculous. Or if you have the $$$, get a Wide Body Kit and then all your problems are solved.
There are three more designations for wheels. One specifies the Contour. While there are many details about the wheel contour, most P-metric radials (typical tires, rather than TRX or other rarely-seen variants) will fit a wheel with a J, JJ, or JK wheel contour. (In other word, don’t worry too much about this as most tires out there will fit your wheels).
The second one is the Lug Pattern and Size. For the Z it is a 5-Lug, 114.3mm Radius Circle Bolt Pattern using 12mm X 1.25 Lugs.
The third one is the Center Bore which is the location hole machined in the center of the wheel and this varies from one vehicle to another. It is essential the wheels purchased have the correct center bore for the vehicle they are to suit, otherwise you may experience balancing problems. On the Z, the Center Bore is 66.1
At the end, if you must know (and you should), the entire specs for the Z32 wheels is as follow:
Front: 16” x 7.5” 45mm Offset 5-lug 114.3mm Bolt Pattern 66.1CB
Rear: 16” x 8.5” 35mm Offset 5-lug 114.3mm Bolt Pattern 66.1CB
Lugs: 12mm x 1.25
What size tires can I run?
overall diameter: 24.86″
overall diameter: 24.68″
overall diameter: 25.32″
overall diameter: 24.71″
overall diameter: 25.03″
overall diameter: 24.58″
overall diameter: 24.85″
overall diameter: 25.09″
overall diameter: 24.48″
overall diameter: 24.75″
overall diameter: 25.02″
overall diameter: 24.49″
overall diameter: 24.73″
Suggested tire width when mounted on:
7.5″: 225 mm
8″: 235 mm
8.5″: 245 mm
9″: 255 mm
9.5″: 265 mm
note: give or take 10 mm. I.E. you can put 245s or 265s on 9″ wide rims.
235/45/17 all around (not recommended for TT)
245/40/17 all around
255/40/17 all around
235/45/17 front, 245/40/17 rear
235/45/17 front, 255/40/17 rear
235/45/17 front, 275/35/17 rear
235/45/17 front, 285/35/17 rear
245/40/17 front, 255/40/17 rear
245/40/17 front, 275/35/17 rear
245/40/17 front, 285/35/17 rear
255/40/17 front, 275/35/17 rear
255/40/17 front, 285/35/17 rear
245/35/18 all around
255/35/18 all around
245/35/18 front, 285/30/18 rear
255/35/18 front, 285/30/18 rear
235/45/17 front, 255/35/18 rear
235/45/17 front, 285/30/18 rear
245/40/17 front, 255/35/18 rear
245/40/17 front, 285/30/18 rear
255/40/17 front, 285/30/18 rear