I just got 4 blizzaks on steelies. So I went from the 2.4's stock 205/50/17 to 205/55/16. So by my half-assed method my trip meter shows a 35.0 mile commute as 36.2 miles. Like a 3.4% change. Is this simply the same error the speedo now has? So if it shows 70mph I'm really going like 68 right?

 

http://www.1010tires.com/TireSizeCalculator.asp


60.4mph on your speedo = 60mph

 

I would say your guess is pretty good.... I dont know the exact differance, but within 1or2mph, im sure.... nothing really to worrie about..... for the most part, its just guys with big lifted trucks and oversize tires, then we are talking about a 10-20+MPH differance

 

Thanks guys! not nearly as much of a difference as I expected.