| Wheels and Tires 101 Ok, since I’ve seen so many posts about wheels and tires and what fit and what doesn’t, and considering there are two very good explanations on the FAQ for each case, I’m going to explain how all those numbers mean and how to use them when buying wheels and/or tires. Keep in mind this is “Wheels and Tires 101” so some explanations will be for simple things that you might already know, so just skip it to the next section in that case. Warning: the information you are about to read is to the best of my knowledge good and accurate, been taken from reliable sources and from years of my own personal experience. I assume no responsibility for misuse or misinterpretation, nor I recommend to act based only on this information. You should investigate many other sources before attempting to buy and/or replace your wheels and/or tires. In other words, you agree not to sue me if you got the wrong tire on your Z and crashed at 180 MPH on the back road next to your house ;)
Wheels
Lets 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).
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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 For more information, look at this excellent write up:
http://www.twinturbo.net/ttnetfaq/FAQpages/rims.html ] ">Wheel FAQ The following is a chart with conversions for those who don’t have a calculator handy and are already going crazy calculating on their mind while reading this: 
Tires I won’t get too deep on what tires to use for the Z as there is a very good write up for the combinations. This is the link:
http://www.twinturbo.net/ttnetfaq/FAQpages/tiresize.html ] ">Tires FAQ Lets just explain how to read the tire denominations based on this example: P225/50VR-16 ( or P225/50R-16 91V ) P Passenger Tire
225 Tread Width in mm
50 Aspect Ratio (see below)
R Radial Construction
16 Rim Size in inches
V Speed Designator Note that the "91" is a load rating, which unfortunately doesn't translate directly into a weight. Note that not all manufacturers are providing their dimensions in this form yet. The aspect ratio is a way of describing the sidewall height, or the height which the tread sits off of the wheel. Rather than give a simple length measurement, it is expressed as a percentage of the tire section width. In the above example, the "50" means the sidewall is 50% of the maximum width of the tire, or 112.5mm (about 4.4 inches). A lower aspect ratio means a lower "profile" tire, which generally means a stiffer sidewall and firmer cornering, sometimes at the expense of ride comfort. People often speak of tires with the same aspect ratios as a "series" of tire, for example, "50-series tires" means tires with a 50 aspect ratio. Performance tires are also given a speed rating to give people some idea of how the tires were constructed and how far they can be pushed. The table below translates speed rating to design maximum mph. Q 100 mph
R 106 mph
S 112 mph
T 118 mph
U 124 mph
H 130 mph
V 149 mph
Z over 149 mph
W 168 mph
Y 186 mph Note that while Z implies performance in excess of 149 mph, two new categories (W & Y) have been recently added to more fully describe their capabilities. In these cases, a "Z" might precede the "R" in the tire size itself, while the "W" or "Y" would appear after the load rating. (e.g. 235/45ZR-17 88W). A tire that is able to take a higher speed is designed and constructed differently than more pedestrian tires. It has lower rotating mass (i.e. moment of inertia) and stiffer sidewall construction, which translates to better acceleration, braking, handling, and cornering, even at low speeds. Furthermore, since tires turning at 140+ mph tend to generate lots of heat, V & Z rated tires tend to be more forgiving if you occasionally overload or underinflate your tires. Keep this in mind the next time you go buy tires for your family van. 
Here is some extra information on little-known facts about tires, specifically pertaining to general highway tires for your daily driver:
- Underinflated tires cause the engine to work harder. It's like riding a bike with low tires. It's harder to pedal because of the increased rolling resistance. - Should you rotate side to side or front to back? Radial tires can be crossed from side to side in the rotation pattern. Bias ply tires should never be rotated from side to side, only front to back. - Not all SUV's come with "P" (passenger) rated tires. Some have the "LT" (light truck) designation. - Underinflated tires wear faster, and they affect the steering and handling of your vehicle. - If tire pressure is too low, then too much of the tire's surface area touches the ground, which increases friction between the road and the tire. Thus, your tires wear out earlier, and they could also could overheat. - One sign of low tire pressure is if your tires squeal when cornering. - A tire can lose up to half of its air pressure and not appear to be flat. - Underinflation is the leading cause of tire failure. It results in unnecessary tire stress, irregular wear, loss of control and accidents. - Tire manufacturers (not the U.S. government) test tires and assign their own grades for treadwear, traction, and temperature resistance. However, there is no prescribed formula for converting the manufacturers' test results into universal grades, so be aware of the fact that numbers from tire to tire are not objective. - Tires lose air at a rate of about a pound a month, which means if they weren't checked since the last time you had the vehicle serviced (say 4 months ago), they could be several pounds low. - Underinflation, by as little as 6 psi, can cut gas mileage by 3%. - Cold temperatures affect the air pressure in your tires. There is a loss of one pound for each ten degrees of temperature drop. - Warning: Never buy a tire with a lower load index or speed rating than your vehicle's original tire! - In the US, regulations require tire manufacturers to grade passenger car tires based on: Treadwear, Traction, and Temperature resistance. Treadwear is based on the wear rate of the tire. A wear rating of 300 to 400 is considered good; 500 to 700 is very good. Further, a tire graded 200 would wear twice as long as one graded 100. Traction grades (from highest to lowest: AA, A, B, and C) represent the tire's ability to stop on wet pavement. Temperature grades (from highest to lowest: A, B, and C) represent the tire's resistance to the generation of heat. - Gas mileage decreases 1% for each 10 lbs of underinflation. - If you're only buying one or two tires at a time, always put the new tires on the rear axle. It's a myth that putting the new tires on your drive-wheel position will give you the most protection; instead, doing so will make your vehicle more susceptible to oversteer (fishtailing or swinging out during fast cornering). - Under-inflated tires wear more on the outside edges. Over-inflated tires wear excessively in the center of the tread. - Use a penny to determine if the tread on your tires is too low. Take a penny and put Abe's head into one of the grooves of the tread. If part of his head is covered by the tread, you're ok. If you can see all of Abe's head, it's time to replace the tire. When the tread is worn down to 1/16 of an inch, tires must be replaced. - Most manufacturers put "P" (passenger car) rated tires on 4WD trucks as well. Some put "LT" (light truck) tires on SUVs and four-wheel drive trucks, but most do not. - The "T" on your tire's sidewall does not stand for Truck, it stands for "temporary" spare. - The "recommended" tire pressure is almost always lower than the "maximum" tire pressure printed on the tire's sidewall. Check your owner's manual to find out where to look on your vehicle for the recommended amount of air (usually on the driver's door, the glove compartment, or the gas filler door). - Since tires can harden and crack with age, you should steer clear of old tires and buy the freshest ones available. Here's how to tell: Every tire carries a U.S. Dept. of Transportation serial number on the sidewall (EX: DOT M6 RV T1HR 499). The last 3 digits are a date code indicating the week and year the tire was made. (EX: the 49th week of 1999).
- Most punctures, nail holes or cuts up to 1/4 inch and confined to the tread may be satisfactorily repaired by trained personnel using industry-approved methods. - For the most accurate reading, tire pressure must be checked when tires are cold. You can check tire pressure any time of the day, as long as the tires have been sitting for a few hours or haven’t been driven for more than a few miles. - Under normal loads, you should inflate tires according to the vehicle manufacturer's recommendations, NOT the maximum pressure listed on the sidewall.
Thanks
Danny Post Disclaimers (as other tt.net members have said):
1. Yes, this might be a repost... Sorry if you are offended.
2. No, I probably did not search to see if someone already posted it. Do you search prior to every post you make here?
3. It might be old news to you, but new news to me and probably as well for some others, so just let it slide.
4. It is MHO, which may or may not agree with yours.
5. Everyone should be and IS entitled to their own opinion and to express it... of course, at times it is best to STFU.
6. If you like it, that is all that matters. Don’t worry what other thinks. Do what you want.
7. Don’t shoot the messenger... really.
8. Relax and cut everyone a little slack, ok?
9. Why can’t we all get along?
10. Enjoy www.geocities.com/miamizcarclub 
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Wheels and Tires 101 - 
