Speedo off?

BULL Crap,
We tested it with a wheel on the outside of the truck, 2 times at the dealer.
Was told it is close enough for them and in the range of what they are let to have.

 

My odo was dead on with stock wheels speedo off ~5% by gps on both. Now with 265/75/16 speedo is really close to on maybe 2% slow ( ~7% increase in wheel travel) and odo is about 3.5-4% off.

 

At first I was like, "Huh?"


...But then I was like

 

See what your error is after 10-15,000 miles on your new tires. Believe me, it will change. Manufacturers probably use something like a 1/2 worn tire diameter in their programming to average the wear. Until they add some type of radar there is no way the vehicle actually has true mph to report - all it has is rear axle revolutions and programming to feed to OBD.

 

mine seems close to accurate with my 265/75/16's, it was low by a couple mph according to my gps