What is the correct backspacing for 35x12.5x15 tires and Bushwacker flat flares?
- Thread starter Drew70
- Start date
That depends on a few factors, are you asking for the correct backspacing to not run components? Or be at the edge of your fender flares? For rubbing we would need to know your lift height (I’m also running 35x12.5 so I can help if you have a 4” lift) in order to determine the correct backspacing.
OP
3 inch Terraflex lift.
Australian laws need to stay within or close to fender edge
Nice also to know best for clearance arms etc
Australian laws need to stay within or close to fender edge
Nice also to know best for clearance arms etc
Okay glad to help! I need to know what style of bushwhackers/width of the flare. I’m currently running a 7” oem style flare (need to be legal and keep clay off my window) and mine sit flush with 4” of backspacing.
How wide are your wheels? How wide are your flares?
If 8", then 4" backspace is optimum. However, with 4" backspacing the tires will still be outside both the stock and Rubicon fender flares. I am not familiar with the width of Bushwacker flat flares so I can't give you a specific answer for your situation [and its late and I'm too lazy to look it up.
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You may be able to use wheels with 4.5" backspacing to tuck in the tires a bit more, but no more than that. You will need to put a washer behind each steering stop to keep the tires from rubbing on the control arms, but that takes only a minute.
If 8", then 4" backspace is optimum. However, with 4" backspacing the tires will still be outside both the stock and Rubicon fender flares. I am not familiar with the width of Bushwacker flat flares so I can't give you a specific answer for your situation [and its late and I'm too lazy to look it up.
]You may be able to use wheels with 4.5" backspacing to tuck in the tires a bit more, but no more than that. You will need to put a washer behind each steering stop to keep the tires from rubbing on the control arms, but that takes only a minute.
OP
And boom just like that we have almost the same setup! 4” of backspacing should be perfect for you to not rub, although depending on how well your axle is centered you might need to adjust your steering stops a bit to prevent rubbing, I didn’t but that’s not an across the board thing. 6” flare should be just flush or less than an inch of tire sticking out!
I just measured my Rubicon flares - a hair over 4". With 315/75R16 tires on 16x8 wheels with 4" backspacing the outer edge of the tire tread is 1" outside the edge of the flare.
Your 35x12.50R15 tires are are only slightly wider so with 6" flares your tires should be completely covered by the fender flares, including the bulge in the sidewall, using 8" wide wheels with 4" backspacing.
.As noted, you may still need to use the washers behind the steering stops with 4" backspace wheels
Your 35x12.50R15 tires are are only slightly wider so with 6" flares your tires should be completely covered by the fender flares, including the bulge in the sidewall, using 8" wide wheels with 4" backspacing.
.As noted, you may still need to use the washers behind the steering stops with 4" backspace wheels
OP
What’s the actual tread width of the 315/75R16? I know the section width is about 12.3”, but I imagine the tread is narrower
I agree 4" works well and is probably the ideal no-problem amount of backspacing for 33 or 35x12.50 tires.
If you need the tires tucked in an extra half-inch you can run 4.5" of backspacing but you'll have to add a washer or two under both of the steering stop bolts. Those would serve to stop the tires from rubbing on the lower control arms when the steering wheel is turned all the way left or right with that much backspacing. I successfully ran 4.5" for a couple years after installing the two pairs of washers. They didn't increase the turning radius enough to notice, I kept them in place after replacing those wheels with a different set with 3.75" of BS.
One thing that's good about slightly restricting how far the steering wheel can be turned with the addition of the two pairs of washers is that it removes some of the stress placed on the u-joints and their 'ears' in the axle shafts that hold them. It's when the steering is turned hard either direction that the most pressure against the u-joint ears on the axle shafts occurs which can result in breakage if you're in a tough wheeling situation. That's how I broke my passenger-side axle shaft, giving it a little too much gas during a hard/max turn while in 4Lo.
If you need the tires tucked in an extra half-inch you can run 4.5" of backspacing but you'll have to add a washer or two under both of the steering stop bolts. Those would serve to stop the tires from rubbing on the lower control arms when the steering wheel is turned all the way left or right with that much backspacing. I successfully ran 4.5" for a couple years after installing the two pairs of washers. They didn't increase the turning radius enough to notice, I kept them in place after replacing those wheels with a different set with 3.75" of BS.
One thing that's good about slightly restricting how far the steering wheel can be turned with the addition of the two pairs of washers is that it removes some of the stress placed on the u-joints and their 'ears' in the axle shafts that hold them. It's when the steering is turned hard either direction that the most pressure against the u-joint ears on the axle shafts occurs which can result in breakage if you're in a tough wheeling situation. That's how I broke my passenger-side axle shaft, giving it a little too much gas during a hard/max turn while in 4Lo.
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Steel City 06 said:
Tread width and section width are going to vary depending upon manufacturer and tire model, but the industry standard nominal dimensions of a 315/75R16 tire are:
Diameter : 34.6"
Section Width : 12.4" (315mm)
The manufacturer lists the following dimensions for my Mickey Thompson Baja ATZ P3 315/75R16 tires:
Diameter : 34.5"
Section Width : 11.9"
Tread Width: 10.0"
The same size BFG KO2's are listed as:
Diameter : 34.5"
Section Width : 12.3"
Tread Width: 10.2"
Therbytj
Member
Jerry, could you help me
running 4” currie lift with 5000x shocks.
35x12.5R15 baja bosses
15x8 procomps with 3.75 backspace
Im rubbing the inner wheel at flex on the anti rock arm at the front, thinking to add a washer or two to the steering stop(I would like to get 3.25 backspace wheel but $$)
Just add one or two washers under the nut welded onto the steering stop bolts. I'm running a 4" Currie with 35x12.50r15 tires on 15x8 wheels with 4" of backspacing.