need help with wheel backspacing

[buck_1one]

I am looking at getting new wheels for my 89 F350 SRW 4X4 and I'm not sure about wheel backspacing. I'm looking at the Pro Comp series 52 black powder wheels. They have two different backspacing for these wheels, a 4.25 and a 2.5. Any ideas as to which wheel backspace would be best? IIRC the tires I will be using are 285 75 16

Here is a link to the wheels I'm looking at (if the link works)

http://www.4wheelparts.com/Wheels/Ro...8.00#ancResult

Thanks for any input.

[Windy in Kansas]

Thanks for any input.
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Just wanted to acknowledge that your post exists. I've never even heard the term of wheel backspacing so cannot provide any kind of an answer at all.

[foxtrapper]

It's not simply a tire size issue, it's where it's going to place the tire in your fenders. You need to measure what your current backspacing is, as well the rim width. Then you're going to measure the clearance around the wheel and tire, and see what either of the two new backspacings will cause it to hit, or nearly hit.

MEASURE CAREFULLY! And don't forget that while the front wheels turn side to side, they all go up and down. So check fender lip clearance and such as well.

[backwoodsman7]

The one with 4.25" backspace says max load of only 2000 lbs. On my '85 F250 diesel, that would leave a payload on each wheel of only 200 lbs on the front, and 800 lbs on the rear. For me, that would make it look like a poor choice, regardless of any other considerations.

[buck_1one]

Originally Posted by backwoodsman7

The one with 4.25" backspace says max load of only 2000 lbs. On my '85 F250 diesel, that would leave a payload on each wheel of only 200 lbs on the front, and 800 lbs on the rear. For me, that would make it look like a poor choice, regardless of any other considerations.

Good point, thanks. It was late when I first looked at them so I didn't think about that. Any idea what the stock rims on a one ton are rated at?

I was hoping someone may have gone down this road ahead of me and could let me know what they found.

I hate the thought of going outside and freezing my butt off to do a lot of measuring. So I thought I'd ask before the freezing begins, lol.

[buck_1one]

Originally Posted by Windy in Kansas

Thanks for any input.
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Just wanted to acknowledge that your post exists. I've never even heard the term of wheel backspacing so cannot provide any kind of an answer at all.

That's too funny. Thanks for the acknowledgment. Have to say that is a first. lol

[oneokie]

For the front tire/wheel assembly, the centerline where the tire is touching the pavement needs to be in line with the balljoint/kingpin inclination line where it would hit the pavement. (these two lines form a narrow V) If these two lines do not match, the steering geometry will be changed, and change how the vehicle handles in turns. (understeer-oversteer) It can also place unsafe loads on suspension parts and wheel bearings/spindle.

If you have a full size spare, measure the backspacing on it. Lay the wheel assy. face down, use a straight edge that is appx. 16.5" long to lay across the wheel, and measure from the bottom edge of this straight edge to the mounting surface of the wheel.