Tech Article: Choosing a set of Aftermarket Wheels
Let's face it, a nice set of flashy wheels will change the appearance of our Zs like no other modification! In today's import explosion of accessories, how do we choose the correct wheel for our cars?
Well, first and foremost, choose a style that you like, since it is your car, your hard-earned cash, and what you will notice every time you walk out to it. While you are choosing a nice set of wheels you should also consider upgrading the performance of your Z. This way you can kill two birds with one stone: a new look and added performance. Usually I would recommend a plus 1 or plus 2 sizing. Say if you are running 215-60-15 on your stock wheels, you should consider purchasing a set of wheels in the size of 225-50-16 or 235-40-17. If your wheels were 6" inches wide I would go to 7" or even 8 inches, if the offset allows them to fit. Your local tire or wheel retailer has an elaborate collection of data on what works and what doesn't so don't hesitate to ask if you can go to a certain size even how ridiculous it sounds (I have gone from a stock 215-60-15 in the rear to a whopping 275-40-17 on a 9.5" wheel; so if you want it, ASK!).
Like an exhaust system that may rob low end torque, bigger is not always better. Although you see 18, 19 or even 20-inch wheels common today, they are for show. When you do see a set of wheels that large that are for performance they are usually machined from very expensive material and are commonly a three piece design to save weight. The sole reason for wheels of that caliber is to fit over massive 14" cross-drilled rotors and calipers. Don't get me wrong, 20 inch wheels can be made for performance, but they would cost as much as a used Twin Turbo Z32 (I don't know about you, but I would rather have an extra car than a set of oh my god! wheels--in reality, I would prefer both).
The reason a cheap heavily made wheel is a bad choice is a simple law of physics: Rotational Inertial. As the distance increases from the center, the rotational force is squared. This is increased more dramatically if the wheel is heavier than stock. So you can see, getting a bigger wheel will actually decrease performance by a minimal amount in terms of directional changes and horsepower to the wheels, but the gains can be well worth it if you make a discriminate choice. Going to a larger wheel will move the distance further from the center which would create more force according to Newton. Rotational inertial makes it hard for a wheel to change direction. The faster you are going, the worst it gets. This includes starting from a standstill. Usually adding a set of wheels in the plus one to plus two sizing will potentially decrease your 60 foot times, but if you have enough horsepower to break your tires loose than the plus sizing can help with more bite which could cancel this effect and even help your times. I have seen cars lose as much as 4 horsepower at the wheels when going from 14" to 17" on a set of expensive wheels.
Racers are always trying to fight this battle of rotational inertial. Aluminum lug nuts, using helium in the tire (a lighter gas than air), cross drilling your rotors, and the most effective - a lighter wheel/tire combo! Are these things important? What if I told you a $150K Porsche comes with aluminum lug nuts. For these same reasons, aluminum flywheels are used to let the engine rev faster to redline!!!
Bottom line? Buy the lightest wheel your budget can get you in a plus one or plus two sizing. If your budget is plentiful than go for the 20 inch, three piece titanium wheels, but don't forget to save some money for a chiropractor since 20 inchers usually run 30 series tires! Hope this helps!
ENJOY YOUR NEW YEAR IN YOUR NEVER ENDING QUEST WITH YOUR Z CAR!