New tires with new size, how to adjust head unit?

I remember reading on how to adjust the head unit to account for new tire sizes... can't seem to find out where, or how to do this. Help please.

(sorry, I know it's been discussed before but I can't find the posts)

 

Hypertech speedometer calibrator will be your only shot at doing this.

 

First figure out whether you actually NEED to adjust anything. Compare GPS speed vs truck's displayed speed.

Going up to 265/70/17 made my truck's displayed speed MORE accurate. It's perfectly in sync with GPS speed now.

 

Really... I swear I thought we could do it directly in the head unit... I'm getting old. SMH

 

I wish we could do it that way, but then we could trick with our odometers from the factory, and Toyota doesn't want that. Soon the hypertech will be discontinued for the same reason.

 

Like 0210 said. 265/70/17's, mine reads 1 MPH faster than GPS at 70 on the highway.

G.