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wheel backspacing

47K views 33 replies 15 participants last post by  Ejwrangler 
#1 ·
what is a better number for not having to use wheel sapcers, 4.9, or 4.52, i am confused as to what number you should be looking for, do you want a lower number, or higher number? And if 4.5 which i hear is the amount you want, is 4.52, an issue, or is it fine. Thanks in advance, about to pull the trigger on wheels and 35's. Just need this answered, cuz i have a couple options. Thanks again. :beer:
 
#11 ·
4.52" Backspacing with 35X12.5" tires should be enough unless you have some tires with a high section width or your suspension configuration causes large axle side shifts.
 
#12 ·
My first rims had 4.75" backspacing and were fine with factory lower control arms, as soon as I put in aftermarket control arms the tires rubbed on the front lower control arms. That was with 36x13.50 tires, when I went to a 37x12.50 they rubbed more and also on the frame, so I added 1.5" spacers. I now run 4" backspacing with no issues. 4.5" is most probably fine, but as others have said a maximum of 4.25" is better.
 
#16 ·
Why must manufactures do shit like that to create confusion. Is that extra little 0.02" of backspacing THAT important to them? Why not just call it 4.5" and be done with it.

To whoever said 3.5" backspacing was perfect, what width of tire and wheel are you running? I think that's a little on the low side to call perfect. I'm on 9.5" wide wheels with 12.50" wide tires and my tires stick way out. With 3.5" backspacing, I'd be 1/2" further out. I can see where you'd want that, maybe, if you're running a 13.50" or 14.50" or wider tire, but with the "normal" 12.5" wide tire, I think 4"-4.5" is about right.
 
#18 ·
Why must manufactures do shit like that to create confusion. Is that extra little 0.02" of backspacing THAT important to them? Why not just call it 4.5" and be done with it.
Maybe because there are folks out there that would complain to the manufacturer that they don't know how to measure Backspacing if they'd say they are "Just" 4.5" ;).
I prefer offset over backspacing for tire position and in this case the offset is likely around -11 or 12 based on 9" wide rims. 0 Offset would likely still work with 35X12.5" tires which would mean about 4.75 Backspacing on a 9" wide rim
 
#19 ·
OK, I could take the time to reseach this a little more, do some math and answer my own question, but I'm feeling a little lazy right now.

I have stock wheels with worn km2 35's and 1.25 spacers now. I am soon to be getting new tires and wheels and want a just a little wider stance than I have now. Would a 9" wheel with -10 offset be about right?
 
#21 ·
Would a 9" wheel with -10 offset be about right?
A 9" rim with -10 offset is about 4.5" backspacing, so most probably okay. Although the two are linked, backspacing is what matters when we are talking about clearance. Traditionally too much negative offset could lead to premature bearing/hub wear, however that does not seem to be a major issue these days. Offset does effect other things like wheel scrub, but on our vehicles it really doesn't make that much difference.
 
#23 · (Edited)
A 9" rim with -10 offset is about 4.5" backspacing, so most probably okay. Although the two are linked, backspacing is what matters when we are talking about clearance......
Clearance to the rim Yes but to the tire?
So lets say the same 12.5" wide tire mounted to
Option 1 --> 8" wide , 4.5" BackSp., 0mm Offset
Option 2 --> 9" wide, 4.5" Backsp. -12mm Offset

A.) Both have similar inner clearances since the backspacing is the same
B.) Option 1 has more inner clearance than Option 2 since the rim is narrower
C.) Option 2 has more inner clearance than Option 1 due to offset
D.) Who cares, Bacon for everyone

? ;)
 
#20 ·
Well stock Moab 17X7.5 got +44.45 mm Offset (I believe) minus 31.75mm (1.25") for your spacers leaves you with +12.7mm offset.
So with -10 offset on the new wheels the center of each tire would be pushed out by 22.7 mm ( a little over 7/8" ) from your setup with stock&spacers.
 
#22 ·
I know this is a total highjack but it's info the OP will probably find helpful.

Any feelings toward wheels with multi fit patterns? A JKO vendor has some wheels on special but I think they're double drilled.
 
#26 ·
Correct me if I'm wrong, experts (that's aimed at Phil mainly :)), but isn't offset more important when talking about cars and backspacing mainly used when dealing with trucks, Jeep, etc.?

I've always preferred to speak in backspacing, too, because it just seems simpler than trying to convert offsets... blah blah blah.

As long as you know you're no closer than 4.5" you're good to go (mostly).
 
#33 ·
^X2
even if you'd find somebody that'd mount that , you'll make it to wherever your first turn would be out of tire store or garage and blow the bead off the 8" wheel. There's also the tierod clearance on a 16" wheel to consider with 4.5" of BS but for most part that should clear unless there are weights adhered to the inner wheel outermost edge near TRE as they can be ripped off from contact due to low clearance room of 16s .
You will want more suitable wheels for running those size tires as said.
Google Search time.
:jeep2:
 
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