I've looked through quite a few threads and couldn't find this. I feel like its probably a fairly common issue though so someone probably knows. I'm putting a '68 to '70 8 3/4" rear end in a '67 Barracuda. What is the backspacing I need on an 8" wheel with a 245 tire. Putting super stock springs on if that makes a difference. Also what is the largest diameter tire that I should be able to fit in there? Thanks.
Rear End Swap
- Thread starter Orange67
- Start date
-
What your looking for is 4.25- 4.5. Just depends on the individual car. My 68 Barracuda I used 15x8 with 4.25 BS. I have 275x60x15 Nitto drag radials.
JoesEdge
Well-Known Member
I figured you can go deeper than that (5+ inches of backspacing), but maybe it's because I have a Duster.
5 " you'll be on the leaf spring in a 67-69 Barracuda.
Your right, I was assuming it was an A body rear? Who knows?
It is a B body housing.
Looks like 60" is advertised drum to drum spacing for that?
A body housing looks to be 57" drum to drum.
So if a A body is 4.5" back spacing at 57" then it looks like I will need a 6" back spacing since I have the longer B body housing?
Can I really get 275 tire in there? I have a 245 now and it looks fairly tight.
Looks like 60" is advertised drum to drum spacing for that?
A body housing looks to be 57" drum to drum.
So if a A body is 4.5" back spacing at 57" then it looks like I will need a 6" back spacing since I have the longer B body housing?
Can I really get 275 tire in there? I have a 245 now and it looks fairly tight.
AJ/FormS
68 Formua-S fastback clone 367/A833/GVod/3.55s
- Joined
- Jan 19, 2014
- Messages
- 24,952
- Reaction score
- 12,303
I put 325/50-15s into the stock tubs of a 68 Barracuda with just the offset spring kit. Those are pretty tight, but they are in the tubs and the body is down over them. Just. There was some massaging.
Before that I ran 295s on 10s. I narrowed the rear to fit a 4.5bs, Cuz I like the looks of the deep dish wheels.
I ran 275s on an old 8.5 inch rim. I'm not positive but I think it was a 3.75bs. That fit on a stock 69, 8.75rear end. Those have plenty of room; miles and miles.
As always measure,measure,measure.
The largest diameter changes with the tire width or where it sits. 295s just fit in there at 27 and change,tall,when properly centered. 275/60-15s are 28 and fit ok if in the tubs. But if they are too far outboard they get dangerously close to the wheel opening at the lower front. There is just enough stud sticking out that you can move the front spring perches back 1/4 to 3/8 inch, and that is enough room.
I once wanted to install 305/60-15s, but at almost 32 inches , that was a no-go,lol. Even 305/50s were too tall, at 29.4.
I think just about any period 8 incher will fit in there. They were usually a ZERO-offset to 1 inch negative at most. A zero offset 8 incher would be a 4.5 backspace. Most period wheels are deep-dish, so the offset puts the bs at maybe 3.5 minimum.
If your wheels have more than 4.5 bs and the tire sidewall gets into the spring, just move the spring or install long studs and spacers. Relatively cheep and/or easy.
Before that I ran 295s on 10s. I narrowed the rear to fit a 4.5bs, Cuz I like the looks of the deep dish wheels.
I ran 275s on an old 8.5 inch rim. I'm not positive but I think it was a 3.75bs. That fit on a stock 69, 8.75rear end. Those have plenty of room; miles and miles.
As always measure,measure,measure.
The largest diameter changes with the tire width or where it sits. 295s just fit in there at 27 and change,tall,when properly centered. 275/60-15s are 28 and fit ok if in the tubs. But if they are too far outboard they get dangerously close to the wheel opening at the lower front. There is just enough stud sticking out that you can move the front spring perches back 1/4 to 3/8 inch, and that is enough room.
I once wanted to install 305/60-15s, but at almost 32 inches , that was a no-go,lol. Even 305/50s were too tall, at 29.4.
I think just about any period 8 incher will fit in there. They were usually a ZERO-offset to 1 inch negative at most. A zero offset 8 incher would be a 4.5 backspace. Most period wheels are deep-dish, so the offset puts the bs at maybe 3.5 minimum.
If your wheels have more than 4.5 bs and the tire sidewall gets into the spring, just move the spring or install long studs and spacers. Relatively cheep and/or easy.
Last edited:
BIGDART72
Active Member
Like AJ said, measure, measure , measure and then measure some more.. don't assume what worked for one with tight clearance will work for you.. ( lesson learned via school of hard knocks). Imo, best guarantee is to find the wheel and tire combo that suits your need/want and build rear to suit that.. but I do understand that budget doesn't always dictate that either...but neither does money spent on a wheel and tire combo that "worked" on someone else ride that wont on yours without mods.
diymirage
HP@idle > hondaHP@redline
i run a a body 8.75 SBP on my duster, and with 4.5 inches of backspacing, and 275/60-15 im dangerously close to the springs
5 inches would NOT work on my duster
DesertRat
Leading edge boomer
I have a 73 A body 8 1/4 with stock suspension running 275/60/15 on my 67 Barracuda using 8"wide rallies with 4.125" custom backspace.
You have a 49 year old car that has probably been owned by several people in that time. Stuff gets abused and what was once within factory tolerances may not be today.
In other words, the leaf springs may have worn bushings, the shackles could be bent, the front mounts could have shifted a bit...
All this means is that you'll have to install the axle and measure once it is in there. You can surely fit a stock 14x5.5 wheel but since you are looking to stuff the biggest that will fit, you should wait.
When I bought my Charger, I took a bare wheel and bolted it up, then saw where I could add width and backspace. I figured for 1 to 1.5" of clearance to the leaf springs and to the outer wheelwell molding. I then took those numbers to order my wheels.
In other words, the leaf springs may have worn bushings, the shackles could be bent, the front mounts could have shifted a bit...
All this means is that you'll have to install the axle and measure once it is in there. You can surely fit a stock 14x5.5 wheel but since you are looking to stuff the biggest that will fit, you should wait.
When I bought my Charger, I took a bare wheel and bolted it up, then saw where I could add width and backspace. I figured for 1 to 1.5" of clearance to the leaf springs and to the outer wheelwell molding. I then took those numbers to order my wheels.
-
