Where is the speed for the speedo measured, the front wheel or the back?

 

transmission

 

So then its not measured by a wheel at all?

Ok, so then what would happen if you got a taller wheel + tire in the back (making your speedo reading slightly low), and got a shorter tire in the front (making the reading slightly high)?

 

It IS measured ultimately by the rear wheels, because the transmission is what causes the rear wheels to spin. A taller tire, one with a larger circumference will cause the speedo to read lower than the cars actual speed. But since the computer controls the speedos readout, a tuner can change what the speedo displays. Front tires have no effect on speedo accuracy. Rim size has no effect unless you change the tires outside height from stock.

 

I know rim size has no effect but Im changing my rim sizes and tire sizes as well, so my front tire diameter will actually end up being slightly smaller than stock and the rear will actually end up being slightly larger. So as far as speedo adjustment which direction would I go? Or would they end up pretty much cancelling each other out?

 

Like was said above; front tire size has no effect on the speedo unless you're driving a front wheel drive car. The speedo calibration is done in the transmission and the transmission speed is only affected by the rear wheels in our cars. The rear wheels are the only thing you need to worry about.

 

K, sweet thanks.

 

if you have no other mods or tune... the dealer can make the adjusments for you so the speedo reads right

 

+1 to using the tuner with rear tire size. Works perfrectly.

 

OMFG Must be stoned...