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Discussion Starter #1
I've got 10 year old Ultra 20" wheels and the chrome is peeling off pretty bad on 1 of them. The Toyo open country tires are within a couple years of their demise as well. I've got an open country 3" lift and am wanting to lower the truck a couple inches to line up with our 5th wheel better.
I can't figure out the whole backspacing dilemma.
My current 305/55/20 do have a little poke, nothing major. I'd like to keep that poke.
I've got about 6-7 wheels that I am looking at, the 2 I am most interested are
Fuel d569 vapor in milled and black matte in an 18x9 as for 1 reason this is the strongest wheel I was able to find in a design I liked.
And also the XD 811 rockstar 2 in matte black.

Here's what I'm trying to figure out.
I read someone say that basically the only thing that matters is backspacing, the other numbers are just subsequent and ancillary numbers derived from the backspacing number.
So what is the backspacing of a stock 07.5 lmm 1 ton SRW wheel? I guess so I can compare the numbers of the new wheels I'm looking at. Both of them show 4.5" backspacing and have -12 offset listed.
Any clarity appreciated...
 

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If it were me I would look up stock wheels and get the back spacing from there. I dont remember my brand of 5th wheel hitch but mine adjusts up and down just a bit. As tires go I would just drop down 2 or 3 sizes to help lower the truck as well. Like 285's and what ever rim you want. I like 16's and 17's there easy to find. I try not to go to wide either or they sit on top of the snow and I have no traction. I all boils down to what your doing with your truck the most. Most loads I carry are in the summer (cows), and most of the winter driving is in deep snow so I use chains usually. Im actually going to just buy a Summer set and Winter set Like we have for the car. You know about deep snow Im sure so just wanted to throw that out there, might put a winter set on the old rims and get a set for summer 5th wheel pulling. Hope this helps more than it hurts.
 

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Discussion Starter #3
Yes mine does raise up and it is all the way up and the corners of the rear top of my bed are very close to the underside of the camper.
If I lower it the rear corners of my bed will hit the underside of the 5th wheel if I go on uneven ground so I can't change the height.
And idk what stock wheels were for my year so idk what to look for to compare them to.



If it were me I would look up stock wheels and get the back spacing from there. I dont remember my brand of 5th wheel hitch but mine adjusts up and down just a bit. As tires go I would just drop down 2 or 3 sizes to help lower the truck as well. Like 285's and what ever rim you want. I like 16's and 17's there easy to find. I try not to go to wide either or they sit on top of the snow and I have no traction. I all boils down to what your doing with your truck the most. Most loads I carry are in the summer (cows), and most of the winter driving is in deep snow so I use chains usually. Im actually going to just buy a Summer set and Winter set Like we have for the car. You know about deep snow Im sure so just wanted to throw that out there, might put a winter set on the old rims and get a set for summer 5th wheel pulling. Hope this helps more than it hurts.
 

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I've got 10 year old Ultra 20" wheels and the chrome is peeling off pretty bad on 1 of them. The Toyo open country tires are within a couple years of their demise as well. I've got an open country 3" lift and am wanting to lower the truck a couple inches to line up with our 5th wheel better.
I can't figure out the whole backspacing dilemma.
My current 305/55/20 do have a little poke, nothing major. I'd like to keep that poke.
I've got about 6-7 wheels that I am looking at, the 2 I am most interested are
Fuel d569 vapor in milled and black matte in an 18x9 as for 1 reason this is the strongest wheel I was able to find in a design I liked.
And also the XD 811 rockstar 2 in matte black.

Here's what I'm trying to figure out.
I read someone say that basically the only thing that matters is backspacing, the other numbers are just subsequent and ancillary numbers derived from the backspacing number.
So what is the backspacing of a stock 07.5 lmm 1 ton SRW wheel? I guess so I can compare the numbers of the new wheels I'm looking at. Both of them show 4.5" backspacing and have -12 offset listed.
Any clarity appreciated...

Nathanp69-

Hope your week is treating you well!

To answer your prior question the 2007 GMC sierra 3500 stock tires were a 265/70/17. Originally came with 17x7.5 wheels that have a 5.39 backspace or +29mm offset.

Offset and backspacing can be frustrating sometimes, however I'm more than happy to help. For myself working with Offset is a bit easier to do the math.

If you know what offset the wheels you have now is you can calculate where the new wheels will sit. If we use your stock wheels as an example, at +29 offset, any wheel that has an offset bigger than 29 will pull the wheel under the truck farther. Any wheel having a number smaller than 29 pushes the wheel away from the truck (in mm). In that example a -12 offset wheel is 41mm farther away from the lip of where the original wheel sat or 1.6 inches.

Wheel offset and backspacing | Discount Tire

Hopefully this provides some help.
 

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Discussion Starter #6
this helps thank you

Nathanp69-

Hope your week is treating you well!

To answer your prior question the 2007 GMC sierra 3500 stock tires were a 265/70/17. Originally came with 17x7.5 wheels that have a 5.39 backspace or +29mm offset.

Offset and backspacing can be frustrating sometimes, however I'm more than happy to help. For myself working with Offset is a bit easier to do the math.

If you know what offset the wheels you have now is you can calculate where the new wheels will sit. If we use your stock wheels as an example, at +29 offset, any wheel that has an offset bigger than 29 will pull the wheel under the truck farther. Any wheel having a number smaller than 29 pushes the wheel away from the truck (in mm). In that example a -12 offset wheel is 41mm farther away from the lip of where the original wheel sat or 1.6 inches.

Wheel offset and backspacing | Discount Tire

Hopefully this provides some help.
 

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Hey thats good info, I always wondered how to truthfully figure offset!!! The 5th wheel problem could get expensive quick just pulling out after getting fuel! Ruin the camper and dent the bed. My buddy uses a Anderson with some sort of adapter for his Gooseneck ball. If you dont mind catching the wind you can flip the axles if your handy, I used to have one that I did that too for dragging with me hunting.Good luck though.
 
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