Any advice on the best offset ,I want to run 20x12.5 x 35

 

No other than 1) that is the wrong format for tire size. What you wrote would be a 20" tall tire, 12.5" wide on a 35" rim/wheel. 2) IMO a 20" rim would look wrong on that truck but to each his own.

 

Ok thanks, I was told by some guys 16" rims and 35" tries is the way to go

 

Stock tires are about 32" tall and a little over 9" wide, and stock wheels have 0 offset.

To have the best handling you want to stay with 0 offset, but going to a 35" tall, 12.5" wide tire there's no way you can do that without way too much tire rub.

Maybe somewhere around 3" negative offset to get the extra width all added to the outside would be a reasonable compromise. But that's just a guess.

As to the wheel diameter, that depends on the look you like and what you are trying to do with the truck. Lots of sidewall (from a smaller diameter wheel) gives a better ride and protects the rim against damage better from pothole and rock hits, so that's generally a good choice on a vehicle that will be used like a truck. A short sidewall (from a large diameter wheel) gives better high speed handling and a cooler running tire, so that's generally a good choice for a vehicle that will be used like a sports car.

Looks are a purely personal thing. Personally I think 20"' rims on '90s vintage trucks look stupid (and I'm not so keen on them on newer trucks either). For a 35" tire I'd go 17" max, 16" preferred, for the wheel diameter. But that's just my opinion. I know others have different opinions and that's fine with me. It's your truck so go for the look you want, not what I want.

 

If you are going to be going off road at all I wouldn't go bigger than 17" wheels. I think by offset you guys mean back spacing. And I would agree that if you're getting a tire that's 3" wider it would be a good idea to get wheels with 3" back spacing.

 

Offset and backspacing are related, but no, I'm talking about 3" of negative offset. That means that the mounting face of the wheel is offset 3" in from the centerline of the wheel. (although in hindsight I think I should have suggested 1.5" of negative offset).

Backspacing is the distance from the mounting surface to the inside rim of the wheel. So 3" of negative offset would mean that the inside rim of the tire is 3" outboard of the mounting surface, sort of like the outside wheel on a dually.

If you want to maintain the handling of the stock wheel you want to maintain the same offset, regardless of the rim width (however that will often lead to tire rub problems as I stated earlier). If you want to maintain the same clearance you want to maintain the same backspacing, regardless of rim width (at some cost to handling).

If the factory rim is 7" wide with 0" offset, that means the inner rim and outer rim are the same distances from the mounting surface, so the backspacing is half of the rim width, or 3.5". If you were to do to a 10" wide rim and wanted to keep the same 0" offset you'd have 5" of backspacing. Or if you wanted to keep the same 3.5" of back spacing you'd end up with 1.5" of negative offset.

 

You can get by with a 10" wide rim with 4.5" of backspacing. It also will keep you from wrecking bearings and balljoints nearly as quick as running 3.5" backspaced wheels. At a minimum you need 16" rims. 15" rims won't clear the brake calipers without grinding material from the caliper, or ridiculous backspacing (2").

I'm running 315/75R16 Cooper Discoverer STT Pros (about 35"x12.5" as far as metric goes) on 16"x10" American Racing Outlaw II's with 4.5" backspacing and have no issues with my tires rubbing anywhere.

Also, for what it's worth, that is WAY more lift than you need to clear 35" tires. A stock 4x4 F250 with springs that aren't clapped out should already clear 33" tires with no issue, and 35" tires with nothing more than a 2" lift in the front. But if that's the look you're going for, go ahead.

 

Thanks I have been wondering what the difference was. I know on my jeep the wheels came with 6" back spacing and I needed to add 1.5" spacers to stop rubbing.

 

For reference, this is my '90 C(F)-350 4x4 on the stock height suspension (with full-length Centurion running boards) with 315/70x17 tires. I intentionally went with 17" wheels because they look better balanced visually than big-*** tires on 15" or 16" wheels (a personal thing).


These tires are 35" in diameter and don't hit anything. I should note that my truck has the stock Dana 60 axle in the front, and that may have a different track that the non-60 front axles. Other folks can comment on that.


Surely an F-250 can't be that much different.

 

Thanks ,for the advice I will put up some pics when I get everything squared away