Fixed.

 

The speedometers are calibrated to the 225's. My truck is stock with 245's. Speedometer was off until I calibrated it with my Superchips programmer. Why they don't do it at the factory is beyond me. I estimate my truck actually has around 4k less miles showing than it really has. And this is legal how?

 

I'm pretty sure the speedos are calibrated at the factory to whatever size tires the truck is shipped with based on the build sheet. If a dealer changed the tire size upon receipt, I'm guessing most would have recalibrated them to match.

 

i idle at 800...

and for those who think the stock tire is 245/75-16 thats wrong. That is the tire size for the 2500's, (maybe the 4x4 1500's not sure) but for a 2wd 1500 it is 2250/75-16. Look on the door jam..

 

Ok it may say that on the door, dont know not at home.

But my trucks build sheet has 245/75/16 and the truck came with them from the dealer and my speedometer is dead on. Dealer did not change tires it came off the truck and in less than 4 hours was at my house

 

^Exactly. The spec for a base level truck may be 225/70R16, but that can change based on the options the truck is actually built with. This will be reflected in the window sticker and build sheet, but not necessarily on the door sticker.

 

i got my truck a few years back with the org tires they were 245/75/16 and the door says 225/75/16

work truck or the cheaper models came with 225/75/16 the nicer ones slt..ect came with 245/75/16.......... now mine talk 2wd i dont know about you 4x4's

 

Yup, checked the door jam and it says 225. Crazy small in my opinion

 

agree its small. and i may be only used in base models. that much im not sure about

 

Did you check your fuel pressure. My truck was donig 8 mpg and I tested my fuel pressure and it was only 18 psi. I put in a new pump (now at 41 psi) and it done 15 6/10 mpg on a 240 mile trip when before it was only making 11.