I have a 04' Dodge 2500 Ram with stock steel/chrome wheels.  I want to put aftermarket wheels on my truck and to make the correct selection, I would like to find out the correct backspacing and offset for the stock wheels.  The factory can't even tell me and at least 3 dealerships have not been helpful.  I have talked to several people with 2003 and up Dodge's who have had problems when purchasing aftermarket wheels.   

I believe the backspacing is 3.75" or so, but dont quote me, I wish I could help more. Might be worthwile to go to a dodge site and pose that question.  

I have and even called Dodge (factory and two dealerships) and neither could tell me.  Go figure.  Thanks  

ok- take off one of your current tires.  lay in flat on the ground with the outside of the tire laying against the ground.  get a straight edge (something that will remain straight when layed a cross the back of the rim.  The straight edge strech from rim edge to rim edge, don't let it hange on the tire.  it must rest only on the rim.  next take a ruler and measure down to the mounting flange, reading the measurement at the bottom of the straight edge.  that measurement is your offset or back spacing you are looking for.

later

Ah, taking the tire off would just be too darn easy though.  

Thanks for the info.  I figured that's what I would end up doing.  I was just trying to take "the road less traveled" approach.  But isn't the backspacing and the offset two different things.  I thought the offset was how far the hub face of the rim was off the centerline of the rim.  That will be harder to figure.   

I guess you've never heard the term "Work SMARTER, not harder".  Enough said.   

different rim manufacturing companies call it different things.  they are the same thing.  just remember the further out away from the spindle mounting flange us the outside edge of the tire is the more stress it puts on the spindle and spindle bearings.  most dealerships are not going to know the answer to those kind of questions  

I guess i just figured someone would chime in with the naswer or way I was correct, which would have been much easier... but who knows?