My fab 9 is narrowed 5.5 in preside looking what wheel offset you guys are running on a 15x12 rim

 

I'm thinking 5.5 bs.
JL will probably know.

 

You're going to need a 4.5 inch backspace unless you're pulling the rim inside the car some to get the tire away from the outer fender lip.

I have a 15x12 on my car with a 5.5 backspace and we took 6.5 off both sides of the rear, 13 inches total. But I tucked essentially a 31x10.5 tire (oversized 29.5 that hoosier makes, 18192 is the part # if you need measurements)

If you haven't bought the wheels yet get ahold of Bob at NRC he's a dealer for sander engineering, good double beadlock wheel for cheap compared to what weld and the like want. It's the american racing track-star wheel that they used to sell, Sander made them for American racing fwiw.

 

Did you move your lca s ?

 

Absolutely they're inwards a good couple inches plus. Built the mounts for them into the 25.3 structure, used a 7 inch long bolt and a spacer where the factory lca's would mount so that they're still "bolted in" with the factory Mounting point.

Sears said ok for x275, ultra ok too when we did it. Wishbone in the rear, the frame rails were notcher all the way I to where the stock shock mounting hole is fwiw

 

JL, I thought you had a 4.5 bs. That's why l said he needed a 5.5 bs because he has an inch more axle that you. So to set his tires in the same as yours, he would need an extra inch of backspacing.
But if you have 5.5 bs he would need 6.5 bs. If he went with 4.5 bs, that would put his wheel 2" out futher that your car.
Am I thinking right. Don't mean to confuse everyone.

I would put the rearend in the car and all the suspension then measure for backspacing.

 

I do the math like this:

stock width rear, 15x10 = 7.5 BS

-5 inches on rear, would be a 2.5 BS

15x12 rear wheel, 4.5 BS

I took 6.5 off each side, so with a 15x12 wheel to sit in stock spot it would have to be a 3.5 backspace. But I pulled the rim inwards 2 inches so I ended up with a 5.5 backspace wheel.

The section width of the tires I have on the rims, which is over 14 inches measured, makes it look like the rear tire isn't pulled in at all, but in fact the rim is inwards 2 inches on the rear. I also have a front end that was built an inch narrow so when you look at the car it doesn't look as noticeable because the fronts are pulled in a little too.

The axle had to be narrowed as much as it was and the tires pulled in so that the outer lip of the fender didn't have to be trimmed, I didn't want to cut that and open it up on the bottom or too much on the bumper cover so that if I ever went to a 275 or a 28 inch tire for a class or something it didn't look stupid with the little tire on the car.

If I did ever put a 275 on the car because of what I did I can run the car so low to the ground that even with the extra 2 foot extension on the rear of my trailer, and the door being long on top of it because of the extra foot of roof height, I wouldn't be able to get it in the car.

I can put the car with a 30 inch tire so that a soda can will not fit under the ground effect, and I can still get up to 8.5 inches of rear lower control arm angle downwards for anti squat, even with the car that low. With the car that low the 3.25 axle tubes are less than an inch away from the frame rail, fwiw. I can literally get the right suspension geometry for a radial with the car as low as a rail car sits. Not saying that would ever work, but I could do it.

315 radial I could run the car really low and still have all the anti squat I'd ever be able to run.

 

Jl if I move my Lca in can I run a 15x12 with 5.5 offset ?

 

You should be able to yes, as long as you're not trying to run a tire that's tall enough to need the lower portion of the fender to be modified for clearance. Unless you're going to do that in that case it doesn't matter

PHB clearance I don't know how that will be, if you are putting a wish bone or are going to relocate the PHB mount then it should be no issue.


If you were closer or in the central CT area for any reason I'd just say stop by and you can see what/how this was done. They look like a std wolfe mini tub but go inwards about 3 inches further than the wolfe kit will go. And I can tell you that the shocks are attached to a bar tied into the cage, frame rails were plated back in with a hefty piece of material, because they're THIN. Real thin, like barely, if an inch thick thin.

Control arms being mounted to the cage and the shocks being mounted to the cage, same with the sway bar and wishbone the frame rails, are really just there. 25.3 structure in the back of the car went all the way thru and attached where the bumper support would normally be so they really see nothing for a load.

 

JL, now I see. You pulled your tire in 2 additional inches. I didn't know that at first.
Now my math works out!

 

I pulled the rim in, the section width of the tire is still wider by a couple inches than the rim. I wanted to put a 15x14 o but there was no way that was going in without having issues with well, no frame rail at all left

 

Happy New Year!

 

JL I'm running a wish bone and moved my lca in 2 in , going to run a 315 radial

 

Also shocks have been moved

 

You should be good to go then. I tried to pretty much make enough room to run any 29.5w tire made, and I think I could just about put a 31x10.5 tire on.

 

I have a 18192 Hoosier on now and it clears, I think the 18221 31x1".5 would fit too as long as this one doesn't rub when it grows, I'm sure the .2'in height won't be enough to be a problem.

By size charts, I think a 3068w m/t 31x10.5x15w would fit if I open up the bottom of the front fender a touch bit. Height wise would be the issue, if I don't like the Hoosier tire I have now I think the next one I will try will be a Hoosier 18221. Sticking with a slick tire,
With what I'm trying to do I don't think a radial is in my best interest.

I dunno how fast anyone's ever even been on a 29.5 tire with stock suspension but that # is likely where I'm headed.