i recently bought an '04 tacoma. when i bought it it had 265/75 16, which were beat. when i drove it home, i noticed the speedo and my gps didnt jive, but i didnt think too much of it at the time, and i think the speedo showed just a little faster than the gps. now i scored a nice set of alloy's with 265/70 16. now the speedo is really off - showing much faster than i am actually going. 75 on the speedo seemed to be about 70 actual. but heres the kinda wierd part. i just ran about 50 miles down the highway using the mile markers, and my odo showed 50.5. its kinda like the math dont add up. i'm somewhat used to driving a vehicle with bigger than stock tires where the speedo shows slower, but this really throws me for a loop, trying to talk myself into the fact that i'm only 70 when the speedo shows 75. i dont know, its just like mental.

what gives?

 

I've got the same problem, and best I can figure is the PO adjusted the speedometer for the larger tires to read accurately. So after putting the smaller 265/70r16's (about an inch smaller than the 265/75r16) your speedometer reads fast.

As far as your speedo reading off but the odometer showing somewhat correct, I don't know. Try a few different trials. Make sure you have a strong gps signal and realize gps isn't *always* spot-on accurate.

Someone else will have to explain how to re-calibrate the speedo/odometer.

Mine reads fast by about 10%, which means my odometer shows 10% more miles than actual. Not an issue for me; I'm keeping that truck til Armageddon.

 

So if I came from 255/70/16s to 265/75/16 my speedo will read somewhat faster? I understand the logic but I am wondering by about how much?

 

Plug in some numbers here and see what you can find out.

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