EB Rim size and offset question & lift question (Help!)

[cgbexec]

I am a newbie, so forgive the long post and amature questions. I am looking at two different rims for an Early Bronco. I know that I need a 5 on 5.5" but I need to know the proper offset. I have not bought the truck yet. I am planning the build first. I am looking to build a mostly streetable truck that will only see occasional light trail duty. My questions are as follows:

1) With cut rears and mild flairs (Not sure on brand) and a 17" x 8" rim, what offset do I need? I plan on running a BF Goodrich LT 285/70R 17. (This is a 33" tall tire that is about 11.5" wide.)

2) Same question, but with a 17" x 9" rim?

3) What is the minimum suspension lift required to clear these? I don't like the look of a large space between the top of the tire and the bottom of the flair. I need it to clear without rubbing during mild trail duty, but I won't be rock climbing. I was thinking either 2.5" or 3.5" bullet proof suspension from Jeff's Bronco Graveyard.

4) Can I clear a 33" x 11.5" tire without cutting the rear? I am thinking that a 31" x 10.5" tire would be max without cutting, but I being a newbie, I don't know what is possible.

I did own a 75 EB about 12 years ago, but I bought it already lifted and just drove it. This one I want to build it over about a year or so just for fun.

 

[cgbexec]

I think that I figured it out. The Micky Thompson Classic II comes in 17"x9" with a 5 on 5.5 with a 5" backspace. The Pro Comp Series 6079 comes in a 17"x9" with a 5 on 5.5 and a 4.75" backspace. American Racing "Mojave" comes in a 17"x8" with a 5 on 5.5" and a 4.5" backspace. Do these sound correct? 1/2" backspacing difference in these rims does not sound like a lot. That has to be the approximate backspacing. Someone chime in if you know for sure.

Also if anyone knows the lift needed to clear these, let me know.

Thanks in advance for any help you can give me.

Chris B.

 

[Skuzzlebutt]

Offset should be around 3.5", maybe 3.75". Some like to have the tires sticking out a little more and go with less.
On my uncut, 33x10.5 rub a bit with 8.5" wide wheels, so you'd need real skinny rims to fit an 11.5 in there.

 

[Broncobowsher]

1) don't know
2) don't know
3) no lift is needed if both ends are trimmed and flared. No matter what you will rub the radius arms unless you adjust the steering stops or invest in long arms with the offset built into them. I ran 33 12.50s for a couple of years without a lift. I actually prefered the way it looked with the tires filling the wheel wells. I was just getting tired of dragging everything on the trail as I started getting more serious so I did a 3½" lift. Not to fit the tires, but to get the body up off the trail. It also gave me a nice ride as well. Then had to figure out the track bar and steering so that would all work right again.
4) I have seen big tires on an uncut Bronco at the Stampede in AZ. Red one, made an issue of 4 wheeler (or some thing similer) a month or so ago as well. I think he was running 35s. Don't know how he fit them in there.

 

[Skuzzlebutt]

Hmm, I was thinking in 15'' wheels. With 17" you could prbably fit a 4.5" offset in there.

 

[Skuzzlebutt]

I meant Backspace, not offset.

 

[Apogee]

Backspacing will also depend on what knuckles you have...the 66-75 Broncos have more clearance between the wheel and the tir-rod end than the 76-77 knuckles. If you want to go tie-rod over or Chevy TRE conversion, that will factor into the equation as well.

Most 17" wheels are going to have a deeper backspacing since they're designed for more modern vehicles. You can possibly counter this with wheel spacers and/or full width axles. If money allows, custom backspacing wheels might be an option as well.

 

[eb66to77]

I have a '74 with '76 knuckles, 16x7 (4" Backspacing) steel wheels, and 245/75/r16's. The fronts rub the radius arms without adjustment to the bumpstops but they clear the knuckles fine. A 15" rim wouldn't clear though.

In the rear the wheels and tires clear everything fine although close to the uncut fenders in the rear. It does clear with my minimal testing at full stuff of both sides, not sure of single side stuff. If you wanted to keep the uncut fenders then You could trim the lip and gain more but don't trim too much as the lip will be weak and you can only clear so much as the body line curves back in a couple inches higher.

 

[ransil]

I have 17x9 3.5" back spacing, 35x12.50 tires.
They do stick out a bit, if you want them to tuck under then 4-4.5" is a better option.
The 17" clear brakes & tie rods.

 

[cgbexec]

Thanks everyone for the help.

Ransil - If you are running a 17X9 with a 12.5" wide tire and 3.5" backspace then if I run a 17x9 with a 11.5" tire and 4.5" to 5" backspace, then my tires should tuck further under the truck about 1 inch to 1.25 inches. I would gain a 1/2" on each side of the tire over yours, but my tire would move under the truck between 1/2" and 3/4" depending on which rim I choose. So technically the inside of my tire would be in the exact same position as yours or 1/4" further under the truck again depending on rim. There may also be subtle differences in tire bulge because you are using a wider tire on a similar width rim. If yours fit, then what I am thinking should be good. Does anyone find a flaw in my thinking?

Thanks guys for all your help.

Chris B.

 

[ransil]

I will take some pictures tonight .

 

[PS]

To restart a semi-dead thread...I'm thinking of going to 17"x9" wheels also and have figured that around a 4" backspace makes sense. I've found some custom wheels I like that I can have made with any offset/backspace I specify; is 4" a safe bet?

Ransil - I'd like to see some pictures of your truck with the 17's, how much lift are you running for the 35's?

 

[eb66to77]

4" will clear any knuckle available but the tires may rub the radius arms depending one the height of the tire.

 

[ransil]

Sorry i forgot to post the pic's.
I just took these a little cramped in the garage.
The 'stick out" from the body is 3" rear 5" front.

 

[PS]

Ransil - Thanks for the pix! Could you do another favor and post a side shot of your truck with the 17's and 35's?

 

[kntr]

I searched and searched for a 17x10" rim with a 4" backspace in chrome. The only company I could find was Ion Alloy. They make a few other options. I ended up with 305/70/17 MTRs.

http://classicbroncos.com/forums/attachment.php?attachmentid=53195&d=1160285450

http://classicbroncos.com/forums/attachment.php?attachmentid=53196&d=1160285450