Good morning. I recently purchased a gorgeous 1994 Z (just days ago) and the car came with beautiful OEM vette wheels and is riding on 235/45 R17s on the front and 295/35ZR 18s on the rear. Stance looks great, ride is fine for around the city, and I am taking several trips around the city on local highways checking all things out even more than I did before on the test drives. No complaints so far, but when I have them, or just questions, I intend to take advantage of all the knowledge on here.
But I was curious about what some of you with more experience with these cars than me might think about when I take a long road trip and going back to stock 16s for an eight-hour drive. Particularly as regards better mileage? Any thoughts or recomendations are greatly appreciated and considered. Thanks, and I am really glad to have found this forum!

 

if you want to get good mileage, find some narrower wheels that fit (i think some of the older v6 cars had 7" wide wheels), and get low rolling resistance tires

 

First question would be - which 16" wheels/tires were on your car from the factory (or are you planning to buy)? The base tires on the Z28 were 235/55-16 (26.1" diameter). If you opted for the "Z-rated" tire option (RPO "QLC") you got 245/50-16 (25.7") tires on the same 16" x 8.0" wheels.

It would appear you are concerned about the increased inertia of the Corvette wheels, and your current tire sizes. Wheel/tire mass only comes into play when you are attempting to accelerate. It takes more inertia to accelerate the mass of the wheel/tire if the center of mass is moved outwards. If you are driving at constant speeds, the inertia of the wheel becomes unimportant, and the tires' rolling resistance comes into play.

If you are working with a constant rolling diameter (one reason we need to know the stock tire size), the center of mass of the 18" wheel/tire may move outward from the axle, compared to the center of mass of the 16" wheel tire. but that change is likely very small. You are adding a bit of aluminum alloy, and subtracting the weight of the two reduced height sidewalls.

Given the fact that you will likely spend most of your time at constant speed, and that the change in center of mass is relatively small, the affect on fuel economy would seem to be minimal.

Obviously at constant speed the rolling resistance of the wider 295 tire is going to be greater than the stock 235 or 245 tire. So that works against the Corvette wheels.

Then there's the issue of the actual tire diameter. The 295/35-18 is a 26.1" tire. That would be identical to the 235/55-16 tire. But if your car had (or you select) 245/50-16 tires, the reduced diameter will increase engine RPM a very small amount at any given speed. That works against the stock wheels.

Bottom line, in my opinion, is don't worry about the affect on fuel economy of the Corvette wheels. The impact would seem to be immeasurable.

While going to a very narrow, high fuel efficiency tire would offer a greater advantage with regard to fuel economy, the return on investment would be negligible. And you would be giving up significant braking, handling and ride comfort capabilities.... I know that from driving my wife's Prius with the fuel efficient tires.

 

Thank you, Fred. That was extremely helpful. I do not have the tires yet, but do have a chance of picking up a set of stock 94 Z-28 wheels from a car being parted out. Your information was more than I expected and greatly appreciated.