so most of us know that a stock s2000 S02 is actaully closer to a 245 than a 225 tire, so lets just assume that for the sake of arguement.

Lets also assume a spanking new tire has a tread depth of what...5mm?

So lets say you wear your tires down bald, essentially taking 10mm off the diameter of the tire (5mm on each end).

According to a rough calculation, that now essentially turns your tire into a 245/45 series. This decreases your rolling diameter almost 3.8%

This means that when your speedo is showing 70mph, your actually going 67.3mph.

Man I get bored on sundays.....

 

I think you might have miscalculated. Did you account for the fact that the tire height also exists on both sides of the wheel?

Overall tire diameter is somewhere around 24 inches or 600mm, so 10mm is closer to 1.7%.

 

lol yeah you get way to bored.

 

but a for the effort