I was looking into a set of wheels probably 22's for my '99 CC. It's 7.4L w/ auto. I talked to a guy here in town that said he had done a few 8 to 10 lug conversions and that the big wheels slowed our gas trucks down alot! Any comment on this from anyone with 2's or 4's?

sounds like the guy in town should drive in those trucks and not just listen to rumors..

Semi's deffinately dont help acceleration, or fuel mileage, or braking. You are adding a lot of rotational mass.

I agree, the average size of wheel/tire combo on a stocker is 29-31", mounted on a steel or a aluminum wheel they are still pretty heavy. The semi's dont change it that much as long as you're not driving like you stole it or have them goofy ass spinners on your ride you should be able to afford to cruise.

yup just like these guys said.

It is not the tire diameter that affects performance. The gear ratio only changes slightly if any depending on tire size. It is not just the weight of the wheels you are adding, the steel adaptors weigh almost as much as the wheels. You are also adding an additional 40 lug nuts and etc. Adding 300 pounds in the bed of your truck is not the same as adding 300 pounds to something that turns. That is the difference between sprung and unsprung weight. I could actually feel the difference in acceleration and braking on my intake/exhaust '05 F-350 on 6 24's. I still love semi's though, in my opinion they "make" any dually.

well said man. and yes x 100 semis make a dually look even more badass. nothing against non semi dually wheels. i have love for them too. haha

The rotational mass you are adding is about 125lbs per wheel/tire/adapter pending on size. This does add to your braking distance and slows your acceleration slightly but these are big/heavy trucks anyways and not many people go out and race them up and down the roads.

On that 7.4, you are probably getting around 10-13mpgs right now and with a set of 22s you probably wont see much of a difference on the highway but may get a drop in stop and go driving.

No worries, a Supercharger to get your faster and a set of huge oversized brembo brakes to slow you down should solve the problem.

lol true haha

Well said! Looks like I'm back on the hunt for wheels and tires.