Pogledao sam tekst na wikipediji Speedometer i sudeci po onome sto u njemu pise a to je:

"...The return spring is calibrated such that a given revolution speed of the cable corresponds to a specific speed indication on the speedometer. This calibration must take into account several factors, including ratios of the tailshaft gears that drive the flexible cable, the final drive ratio in the differential, and the diameter of the driven tires. The speedometer mechanism often also drives an odometer plus a small switch that sends pulses to the vehicle's engine computer... "

Tako da sad uvek ides brze nego sto na brzinometru pise. Jedino sto je to brze samo 1.077 puta... Znaci ni 1%. A konvencionalni brzinomeri imaju nepreciznost od oko 5% tako da nemas razloga za brigu ;)

zahvaljujem

www.miata.net/garage/tirecalc.html

nasao sam kalkulator pa koga zanima nek proba.