So the night we bought the truck we pull onto the interstate. I set my cruise for my normal limit +10 and so does my wife in the Audi. She then proceeds to run off and leave me.

So I figure my spedo is off and I'll have to get it looked at.

After getting my build sheet yesterday it hit me. The truck left the factory with 265/70R17 tires and I would assume was calibrated to that.

It now has 245/70R17 tires giving me about a 3% error in the spedomenter.

My question is about the door sticker. It calls for the 245s. Would Dodge have put the optional tires on at the factory and not changed the door sticker to reflect that?

 

I really doubt that, but you never know what a dealer might do once they get the truck. Especially if its used. I bought my truck used from a dodge dealer with about 20,000 on it and they never changed the plugs. Dealers are penny pinchers and ifit saves them a few bucks to stick smaller tires on it, they will.

 

By door sticker I mean the one with GVWR and such on it. The VIN on the sticker matches my plate so I know it's not bogus.

Dealers aren't authorized to issue new stickers like that are they?

 

I am not a tire expert, but is my understanding that the 265 or 245 is the width in mm of the tire. The "70" is the aspect ratio of the tire, height to width. If the aspect ratio changed, then I could see a speedo difference. Unless I am missing something or I am mistaken, I don't think going from a 265/70R17 to a 245/70R17 would make a lick of difference, other than how much rubber is on the road width wise. My guess on the tire change from the factory sticker is that someone before you bought atruck from the dealer and wanted the wider tires, so, the dealer swapped them out, giving your truck the narrower ones from the other truck.

 

Not that I know of.

 

You are correct, That is the width. you get your height from your aspect ( the height of the sidewall) and rim size. Did it mention any rearend work, or new tranny?

 

The "70" in the tire size is a percentage of the width of the tire therefore a 245/70 is smaller than a 265/70
Heres a handy way to check that out
http://www.discounttire.com/dtcs/infoTireMath.dos

doing 65 mph the speed difference would be a little more than 2 mph

 

Okay, ignore this bloody redneck. (that being me)lol.

 

Effectively it's about a 1 inch difference in diameter.

What I'm confused about is why the build sheet would show the larger tires but the door sticker (GVWR and such) not reflect them being installed.

 

Got me beat on that one. My vote is usually gonna be dealer dyslexia.