effect of rearend gearing on ET's

You are using a mathematical formula to simulate something that can't be simulated well. So your results are skewed. It doesnt take into account your clutch (assumes 0 slippage I'm sure), doesn't account for the car's suspension (again, assumes an average reaction), doesnt look at wheel spin past teh initial launch, and doesnt look at the driver, who is the single biggest limiter in most 4sp cars. It's like trying to figure out what a recipe from the internet will taste like by reading the PC screen. You can imagine it, but little else until you make it and try it. MPH indicates true potential in reality. If you run 114 but take 13.1 seconds to reach it, you have a lot of room to improve. That's all you need to knew really. I gear a car for what I do with it. If you drive it daily, don't run 4.56s...lol. If you are racing it, you'll go faster with more gear. A 28" tire should have a roll out of 87-88". Roll out is the length in inches the tire needs to make one full revolution. I have no idea why they ask tire diameter if they also as roll out. At least that's what I recall it being..lol.