thanks jsmith. I hate buying things like this that I have very little understanding of. My luck I order stuff im not happy with and seems like I always pick a dealer that misleads me or doesn't really know that much haha

 

9 inch wheel centerline is at 4.5 inches. -6mm (about a quarter inch) Leaves 4.25 inch backspacing.

 

Industry standard centerline for backspacing is .5" outward. For instance a 8" wide wheel with 0 offset is 4.5" bs not 4" bs and a 9" wide wheel would be 5" centerline so -6 would be 4.75"

 

I haven't read that anywhere.... Do you have a source to back that up? (I am always interested in learning. This is NOT a knock toward you.)

 

The chart I posted earlier shows it. Here's a few examples of different wheels-
17x9 -5 4.75 bs
http://www.ebay.com/itm/American-Eag...BVjgB7&vxp=mtr
17x9 -12 4.53 bs
http://www.ebay.com/itm/17x9-Black-Wheel-Ballistic-Morax-845-5x135-5x5-5/161946729194?_trksid=p2047675.c100005.m1851&_trkparms=aid%253D222007%2526algo%253DSIC.MBE%2526ao%253D1%2526asc%253D20131003132420%2526meid%253Dd439adcc6eac484388c13d7341c053d6%2526pid%253D100005%2526rk%253D2%2526rkt%253D6%2526sd%253D14115796217315x8 -13 4.0 bs
http://www.summitracing.com/parts/crr-3975812/overview/
17x8 0 4.5 bs
http://www.jegs.com/i/Black+Rock/262/997785045/10002/-1
16x8 0 4.5 bs

I had it explained to me why it's done this way but it was many years ago and for the life of me I can't remember why it was

 

Well that's just bizarre...... Leave it to some corporation, or, a collection of them, as the case may be, to make things more complicated than they really need to be....

Thanks for the enlightenment.

Would be nice if they wouldn't mix and match their units of measure though.

 

So that same rim in 8 bolt, Ballistic 845 Morax 17X9 8x165.1 -12mm Flat Black Wheel Rim, says 4.50 backspacing -12mm offset, the offset doesn't really mean anything towards backspacing?? THe backspacing is what it is at 4.5" which is what stock rims on this truck would have been?? although I am wider with a 9" rim and putting 35"x12.5x17" tires on them.

 

The offset along with rim width is how you figure out the backspacing, offset by itself won't tell it to you. A 8" wide wheel with -12 offset would be 4" bs while a 9" wide wheel with the same -12 offset is 4.5" bs.
It does show there were 2 different stockers for your truck
http://performancelifts.com/wheel-ba...formation.html
one set has 4.5bs and the other 6.2bs so to figure out which you have you can lay something flat(I usually just cut a piece of cardboard to fit) on the inside rear lip and measure down to the center.

Also something to keep in mind is even with the same backspacing those new wheels are wider and the extra inch+ will be going outward so it should give you the look you want.

 

And will I be o.k. putting 35 x 12.5 x17" on a 9" rim. Is that pretty typical.

 

9" is just right, you could even go 8" or 10" depending on what look you are going for. I have 8" wide rims with 12.5" tires on 3.75" BS steelies and it gives a good amount of tire outside the fender (approx 2.5-3") and would definately look correct with fender flares. With a 9" rim I believe you would want 4.75" to get a similar look, but the rim would be 1" further towards the center of the truck (which should be OK). Decreasing that would push the rims out even further.

Can you post pics of these flares on your rig? I am very interested in seeing how they look. I've always loved pocket flares but hated how the Bushwacker and Ruff Riderz ones look on these trucks. I knew Lund made some but can't find any pics.