Tires and Speedometer

[DelmarvaXJ]

I've been reading around and could'nt find an answer, hopefully you guys can clue me in... I know with any vehicle once you increase the overall tire diameter over your stock tire height, your speedometer will not read correctly(MPH). So how do you know how far off you will be in MPH based upon your increase in tire size?(with out pacing another car) I bet there's a formula or calculation to figure this out, because I'm assuming that my speedo will be way off when I upgrade from stock 28-29" tall tires too 33's.

 

[Tim_MN]

Calculate speedo error -

http://www.bfgoodrichtires.com/bfgapp/popups/demos/demos_pickuptruck_0.jsp

 

[redneck]

Thats the best calculator that I have seen. I have always used this one, http://www.bgsoflex.com/rpmmph.html

 

[redneck]

Calculate speedo error -

http://www.bfgoodrichtires.com/bfgapp/popups/demos/demos_pickuptruck_0.jsp

 

[DelmarvaXJ]

thanks guys