well i read the sticky and am still lost. i am lookin at a set of 16x8 rims with -6mm of offset and 4.25" of backspacing. i would like to know if these rims will sit under the truck like stock or stick out. :confused:

With that wheel size vs. stock size that 16x8 wheel will be sitting 1.7" closer towards the truck than the stock one. Here is a website that helped me a lot when I was deciding on a wheel & tire combo for my truck.

http://www.rims-n-tires.com/rt_specs.jsp

so what is the offset of a stock rim?

My stock setup was with 245/75 16 on a 16x6.5 wheel with a +28mm offset and 4.875" backspacing

not to sound like an ass! but here I go:

Back Spacing is a measurement taken from within the inside of the rear side of the wheel. This measurement is important to be sure you have proper wheel clearance for your specific car (http://www.ehow.com/how_2113075_measure-back-spacing-car-wheel.html#) before purchasing new wheels.
Instructions

Difficulty: Easy
Things You'll Need


Tape Measure
Flat yardstick or similar item with a flat edge, at least as long as the wheel from end to end.Steps

1
Step One

Lay the wheel on a flat surface, front side facing down.

2
Step Two

Lay the yardstick across the top of the rim, from one side to the other. If there is a tire on the wheel you must then lay a flat edge (http://www.ehow.com/how_2113075_measure-back-spacing-car-wheel.html#) the correct size of the rim, from one side to the other, which will lay flat onto the edge of the rim, not the tire.

3
Step Three

Measure the distance from the inside mounting surface of the wheel, where the lug nut holes are, which mates against the axel hub on the car, to the lower edge of your flat ruler/stick lying across the top edge of the rim (http://www.ehow.com/how_2113075_measure-back-spacing-car-wheel.html#).
This measurement is your "Back Space" measurement!

do that on both rims and you will know the difference!

this might also help
https://www.rsracing.com/images/tech-wheeloffset.gif

With that wheel size vs. stock size that 16x8 wheel will be sitting 1.7" closer towards the truck than the stock one. Here is a website that helped me a lot when I was deciding on a wheel & tire combo for my truck.

http://www.rims-n-tires.com/rt_specs.jsp

Use the tire and wheel calculator noted above. You will find that compared to the stock wheel, the wheels you described --16 x 8 with -6mm offset will push your wheel farther to the outside. It will stick out 1.3" more than stock.

Use the tire and wheel calculator noted above. You will find that compared to the stock wheel, the wheels you described --16 x 8 with -6mm offset will push your wheel farther to the outside. It will stick out 1.3" more than stock.

Oops, my bad, I don't know where I came up with that number, I must have punched in a wrong number. Now that I tried it again with http://www.rims-n-tires.com/rt_specs.jsp it said that the new combo will stick out 2.1" farther than stock.

olboy82 - not to worry.. just a -- 'oops'
diesel4life - I just put new wheels on my truck (see signature). They have 4.5" back spacing, and with the tires stick out 1.5" farther than stock. It looks fine and not as noticeable as you might think. Be careful of going to little of backspacing and pushing the wheels out too far. It adds a lot of stress to the bearings.

so not to highjack thread but what is the best backspacing and offset for a 16x8 rim that fits the nbest like stock?no rubbing issues?