I can NOT for the life of me get the speedo corrected.
Going 50 mph as indicated on the speedo and aswell as the computer, i am actually going 46. Friend who is a cop clocked me and also i was on my GPS. GPS agrees with police radar. (to verify that the needle wasn't removed and replaced incorrectly previous to me owning the truck i also ran the HPT scan tool and it agreed with speedo needle).
I had a diablo tuner before HPT, the handheld decide to crap the bed on me so the "stock" tune i read when I got HPT was actually a diablo tune, but i have compared my diablo stock tune to a repository tune and i could not find anything at all that was different between the two.
I am going from the stock 245/45/16's to a 285/75/16.
the 285's measure 32.8 diameter.
BUT, i can put in any number and I STILL get the same readings on the speedo, nothing I do has made a change.
Am I missing a critical step somewhere here?!
The last three years my speedo has been approx 9-10% fast, which I would assume the odometer is affected also. That runs my milage that I have put on up just that much more.
Truck currently sits at 77K miles, which is ACTUALLY 72K miles...