18 backspace 5/7 drop

[superwade57]

I searched and didn't come up with any solid answers, looking for backspace on a 76 swb fleet with a 5/7 drop. Looking at probably 18x8 up front and 18x8-10 in the rear. Any backspace suggestions and or pictures please

[SkinnyG]

Since the overall tire diameter isn't likely to change, you probably want the same backspacing as the 15's use: 4" backspace for the 18x8's, and 5" for the 18x10's if you want them to tuck.

[superwade57]

Awesome thanks!

[Bmstd]

I was looking to do similar wheel tire option recently with my 85 swb.
I have a "Tire Mate" tool and did some sizing with following:

Rear - 295/45ZR18 with 18"x10" rim and found you can accomodate a backspace of 5" to 5.5" with 5.25" optimal.

Front - 255/45ZR18 with 18"x9.5" rim and found you can accomodate 4.5" to 5.0" of backspace, but on stock A-Arms with McGauphy's 2.5" drop spindles you would want to stay toward 5" backspace to avoid hard rub on wheel opening and outer inner fender. Just for fun, i trial fitted the 295/45ZR18 on the front for 9.5" rim and found it to be feasible if i use 73-80 inner fenders or remove all together and make my own.

Since you have a 79 model truck the inner fender well is more open and rounded and will have little less interference than what is used in the 81-87 trucks. Remember, the front track width is wider than the rear. You can also consider narrowed A-Arms from porterbuilt to take off 1" off each side plus move the wheel back forward in the wheel opening if you want to get more precised in aligning your tracking from front to rear. Also this gives you option to have more deep look to front rim for that cool road race look.

[superwade57]

Great info! Thanks!

[G8DAN]

Hey Bmstd,

When you fit the 295s up front how did it fit? I want to run 295s or 285s up front soon on a 18 by 9x5 wheel.

Were the 9x5 5.5 backspacing?

[school boy]

Im running 295/50/15 on 15x8 wheels with I believe 4" back space.I completely clear the factory arms with 2.5 drop spindles but barely.

[DubDubU]

I have 18x8 rims on front with 245/45 tires and 4.5" bs. On the back 18x10
rims with 295/45 tires and 5.5 bs. 3/5 drop except sagging front springs make it more like 5/5.

[Bmstd]

Hey G8DAN

When i trial fitted the 295/45 18 on front i found 5.0" backspace to be one of the best options with stock front A-Arms. You could try to go with more BS, but you may run into major rub issue with inner fender and frame and suspension at full turn.

As is state earlier, you will need to trial for your year of pickup and your suspension height. I am only giving a guide to what i found would work with my set up. These old trucks can be very tempremental based on original or complete rebuilt which all can factor in what you have for room even from side to side on same vehicle.

[Malo83]

Originally Posted by DubDubU

I have 18x8 rims on front with 245/45 tires and 4.5" bs. On the back 18x10
rims with 295/45 tires and 5.5 bs. 3/5 drop except sagging front springs make it more like 5/5.

Nice!! I,m looking at going with the same rim package, any more pics of the truck.

[G8DAN]

Thanks for responding.

In my research, I originally came to the conclusion that 5.5 backspacing would work on a 9.5 wheel. So your 5.0 info is very helpful. I Appreciate it.