Actually, all of you are somewhat wrong, and somewhat right. I just busted out one of the old SCC's I had and it had a fat test called
POWER, WEIGHT, GRIP!, and they are testing the 1/4 mile time and speed with 16, 17, and 18 inch wheels. Anyways, the 18 inch wheel and tire combo actually weighed less than the 17 inch wheel and tire combo due to the 18's weighing 1 pound more than the 17's but the tires for the 18's weighed 2 pounds less than those of the 17's.
What they concluded from the testing were that ......
"The fact the 18-inch wheel was slower, despite being slightly lighter than the 17 suggests that rotational inertia is, indeed, a significant factor in acceleration. As weight is moved outward, rotational inertia increases with the square of the distance from the center of the wheel. Not only was the wheel rim a half-inch farther from the center (which alone would account for a 12-percent increase in rotational inertia), but the 18-inch wheel was 8 inches wide while the others were 7, making the rim a larger percentage of the wheel's weight.
But wait. Going from 16-inch wheels to 17-inch wheels also added weight and increasedd rotational inertia, so why wasn't there a bigger difference there? This inconsistency hints at the fact that there is some noise in our data. Even with a consistent car and a consistent driver, there are too many changing factors in a quarter-mile run to expect exact repeatability. While the trend seems correct, random variations seem to have slightly overstated the difference between the 17 and 18 inch wheels, and understated the difference between the 16s and 17s.
This is a clip from under a picture of three wheels on scales.
Contrary to popular belief, bigger isn't always heavier. All of our Enkei/BFGoodrich wheel/tire combos were relatively light. The 16s weighed in at 44.4 lbs, but the 17s and 18s were 47 and 46 pounds respectively."
All were both wheels and tires.
Case closed. How far the weight from the center does play a role along how much weight is added.
BUT, the difference was minimal.
LAP TIMES AND PEAK SPEED BY WHEEL SIZE
2000 Mitsubishi Lancer
Wheel Size Lap Time Straight Speed
16 inch 1:03.7 96.1 mph
17 inch 1:03.2 95.5 mph
18 inch 1:03.9 95.0 mph
QUARTER-MILE TIMES BY WHEEL SIZE
2000 Mitsubishi Eclipse GT
Wheel Size 1/4 et/mph
16 inch 15.5 sec. @ 89.4
17 inch 15.5 sec. @ 89.0
18 inch 15.6 sec. @ 87.9
Case closed.
So from what I've gathered the wheels I plan to purchase will be 18 inchers that'll weigh less than the stock tire/wheel combo will just about equal out, and should expect same times as with stockers. I might even return better 1/4 mile times due to the fact the tires will have much more grip than the stock tires. So who knows...
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