Nominal Offset

[BIG Laing]

While looking through the 2011 f350 specs I came across the wheels and tire section. And I had a few questions. Correct me if I am wrong.

Both the 18" and 20" wheels are 8" wide.

And the nominal inset (+ offset) is 40.

My biggest question is about the nominal Inset, Is this what the wheels actually are? Or what they should be to have the wheel centered over the hub?

I am confused becuase I read a thread on this site that said the 18" wheels are 8" wide and have a +40 offset. While the 20" wheels are 10" wide and have a +19 offset.

Thanks

[Painted Horse]

The 20" OEM wheels are also just 8" wide. They are not 10" wide
The 2005 and later wheels have a greater offset than the 1999-2004 trucks. As Ford widened the axles in 2005 requiring the larger offset.

[BIG Laing]

Anyone know?

[tonydumpsters]

to big Laing in order to understand wheel offset, you need to start with the basics ..if a rim like ford is 8" wide..and says plus 40, this means it has a 40 mm positive offset..essentially, if you had a zero offset your rim contact point on the rotor would be at dead center (which would be a zero offset) with this being said , as you move that point of contact closer to the front of the rim,you have a positive offset..as you move that point of contact to the back of the rim you have a negative offset or an old school DEEP DISH rim,,,it is easier to google offsets so they have a picture to look at..hope I explained this in "simple terms"

[BIG Laing]

Originally Posted by tonydumpsters

to big Laing in order to understand wheel offset, you need to start with the basics ..if a rim like ford is 8" wide..and says plus 40, this means it has a 40 mm positive offset..essentially, if you had a zero offset your rim contact point on the rotor would be at dead center (which would be a zero offset) with this being said , as you move that point of contact closer to the front of the rim,you have a positive offset..as you move that point of contact to the back of the rim you have a negative offset or an old school DEEP DISH rim,,,it is easier to google offsets so they have a picture to look at..hope I explained this in "simple terms"

Sorry I know your trying to help but that is not what I was asking. I know what an offset is. I know how that affects backspacing. I know how to figure exactly how one wheel differs from another wheel. I know that a + offset is actually called an inset.

What i don't know is my original question on this post. Are the stock SRW
F350 wheels (18x8 and 20x8) actually a 40 inset (+40 offset)? Or is that what the trucks optimal offset is?