Wheel bolt pattern confusion

[kat]

The tires Im looking at is 12 wide also, and to let you know Im running stock axles/rearend. You were talking earlier about hub size, what is the hub size on the Broncos??

 

[sykanr0ng]

The tires Im looking at is 12 wide also, and to let you know Im running stock axles/rearend. You were talking earlier about hub size, what is the hub size on the Broncos??

Unless you are running some kind of very low profile tire usually the width of the wheel is supposed to be less than the width of the tire.

 

[lonesouth]

I just happen to have a set of 2" spacers that I don't need anymore. You are welcome to try them out to see if they will work for you.

 

[Apogee]

Most people would run an 8-10 inch wide wheel with a 12.5" wide tire per the tire manufacturers' recommendations. I personally have run 8" wide wheels on 35x12.5" tires, 10" on 33's and 35's, and my next set that I'm setting up for now will be 9's on 37's. Even though I don't prefer the look of stretching out the tire sidewall, the real issue is how exposed and unprotected the lip of the wheel becomes in such an installation, not to mention the inability to air down to any level that helps off road without risk of losing a bead...that said, do what you like.

In this case, bigger is not necessarily better IMHO, so maybe it's time to rethink your go big or go home position.

 

[sykanr0ng]

Most people would run an 8-10 inch wide wheel with a 12.5" wide tire per the tire manufacturers' recommendations. I personally have run 8" wide wheels on 35x12.5" tires, 10" on 33's and 35's, and my next set that I'm setting up for now will be 9's on 37's. Even though I don't prefer the look of stretching out the tire sidewall, the real issue is how exposed and unprotected the lip of the wheel becomes in such an installation, not to mention the inability to air down to any level that helps off road without risk of losing a bead...that said, do what you like.

In this case, bigger is not necessarily better IMHO, so maybe it's time to rethink your go big or go home position.

Maybe something like this is what he is planning on:

 

[DirtDonk]

The tires Im looking at is 12 wide also

Agree with the others kat. If you're going to be running a 12 or 12.50 inch wide tire, the best fit for an EB is going to be between 8" and 10" wide. I prefer the narrower end of the spectrum myself, but in the past the 10 inchers seemed to be the go-to size for most.
Whether with modern metric sizes such as you would most commonly find with your 20" wheels, or even the older "flotation" sizing, just make sure to check and stick with the manufacturer's recommendations.
And here again, because they're modern 20's and not necessarily specified for older vehicles, be sure to look for an application such as the Jeep CJ's for proper hub sizing.
I forget what the actual size is (3.25" maybe?) but it's much larger than most modern trucks. The alternative, if you just can't find a wheel you like with the proper hole size, is to have a machine shop bore the center hole out to a size that will fit over your Bronco's front hub.

For offset/backspacing (two different methods used to describe similar (but not always identical) characteristics), that's a tougher nut to crack. You're usually looking for a compromise between fitting (not rubbing something inside) and looks (not sticking out so far as to make your EB look like a skateboard) and that takes some figuring. Some people actually like the skateboard look, while others just like to see some of the tire sticking out past the flares. Others prefer flush with the flare for a more "stock-ish" looking rig.
If you can compute the backspacing from the offset numbers, or can find that spec in the manufacturer's info, try to stick with 4" to 4.5" I think. Less than that is going to be hard to find in a 20, and more than that might be tucked in a bit tighter than optimal. Still, there's always a little variation you can get away with. Almost...
There are more and more owners using those tire sizes, so maybe some with those can chime in and let you know what they settled on and how it worked out.

Depending on the overall diameter of the tire (you didn't say here either I don't think) just about anything over a 31 is going to rub the radius arms if the wheels are tucked in. And pretty much anything over a 33" is still going to rub the radius arms with the wrong offset.
With the 20's, as mentioned the clearance on '76/'77 disc brake knuckles is usually a non-issue, so it's just the radius arms that will be in the way.
The only real "problem" with rubbing the arms is noise and loss of turning radius. It's not going to hurt either the arm itself, or likely even the tire. But it's definitely something to factor in. After all, there's only so much room built in to a factory wheel well, and when you go changing things drastically in multiple dimensions from what the designers envisioned, it's up to you to make comparable modifications to other stuff to make it all work together.

There are steering stops built in to the knuckles that you can adjust/modify to keep the tires from rubbing, but that means you can't turn as sharp. You can keep moving the wheels out until it clears, but likely you'll be in that skateboard category I mentioned earlier.
So choose your desired tire size carefully, and make the wheels match your tastes and the factory limitations the best you can from what info you gather here.

You were talking earlier about hub size, what is the hub size on the Broncos??

See above, but still not 100% sure. That's one of those numbers that for some reason I'm never sure about. Someone will know for certain though, so wait for confirmation.

Good luck. Wheel choice is almost as hard as paint choice!

Paul

 

[kat]

A lot of good information there. And I do realize that a 20x12 rim is not very common. I have been on the fence with what size rim to run and I know a lot of folks on here don't like/or think they are redonkilous running such a big rim. But I live in Florida, there are NO rocks down here and Im not going to do heavy mud bogging. This is going to be a daily driver and to pull my boat to the river/lakes. I will have a 6 1/2 lift on the Bronco when I put my new set of shoes on it. They will be a 35. I have talked to a few guys about the backspacing/offset issues, and I THINK Ill be ok. But before I plopped the money down, I will be talking to the company Im purchasing them from to make sure I wont have any issues.
But don't think for a moment all this advice is falling on deaf ears. Any knowledge I can take away from this website is great thing. I have searched on here for Offset/backspacing threads and all though there are many, not many with the size of rim Im looking into. A friend of mine has givin me a website that deal with a lot of these rim sizing issues so I will be giving them a shout to get even more info before I drop the money.

DirtDonk you are very right about wheel/tire choices, I didn't think it would be this tough...I have been searching on here on readers rides trying to find what looks good to me. Color not an issue since I knew the color I wanted when I decided to buy a EB...