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post #1 of 30 Old 05-19-2011, 06:50 PM Thread Starter
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wheel backspacing

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.
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post #2 of 30 Old 05-19-2011, 07:23 PM
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two hundreths of an inch ain't gonna make a difference on the 4.52" compared to the 4.5"

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post #3 of 30 Old 05-19-2011, 07:25 PM
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backspacing is measured from the BACK of the rim to the mounting surface of the wheel. IE: a 3" backspacing sticks out an inch more than a 4" backspacing wheel.

I am running 3.5 on my 37's and Bev is running 4" on 35's

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post #4 of 30 Old 05-19-2011, 07:27 PM Thread Starter
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thank you, so i am good with 4.52 then, done. about to press purchase right now, lol.
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post #5 of 30 Old 05-19-2011, 07:43 PM
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I would think you would atleast want 4.25 BS. That is what is usually recommended for lifted vehicles.
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post #6 of 30 Old 05-20-2011, 04:09 AM
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im also running 3.5" no spacers needed... for me 3.5 is perfect for 37's and most larger tires..
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post #7 of 30 Old 05-20-2011, 05:11 AM
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i have question not to take over your thread or anything but what size spacers do i need to get for a 3 inch lift and do i need it on all 4 tires or just the front sorry im really new to all this
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post #8 of 30 Old 05-20-2011, 05:18 AM
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Quote:
Originally Posted by jakefister11 View Post
i have question not to take over your thread or anything but what size spacers do i need to get for a 3 inch lift and do i need it on all 4 tires or just the front sorry im really new to all this
well it depends on what backspacing your wheels are ... if you have atleast 4.5 backspacing you should be ok without a spacer... and yes if you need them you would need 4 of them..
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post #9 of 30 Old 05-20-2011, 06:18 AM Thread Starter
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Originally Posted by block View Post
well it depends on what backspacing your wheels are ... if you have atleast 4.5 backspacing you should be ok without a spacer... and yes if you need them you would need 4 of them..
I know i would need four of them, i have just heard that you need at least 4.5 in of backspacing, and the wheels i found that i like for a price i like at the exchange are 4.52 in of backspacing, i was inquiring if that is sufficient enough to not run spacers. So my question is, is 4.52 in of backspacing good enough to bnot run spacers on 17x9 with 4.52 in of backspacing and running 35/12.50's. Thank you for any responses, i am waiting for the right response to pull the trigger.
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post #10 of 30 Old 05-20-2011, 06:55 AM
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I'm running 37's on 4.5BS. No touching with axle centered. But I find out quickly it was not centered.
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post #11 of 30 Old 05-20-2011, 06:56 AM
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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.
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post #12 of 30 Old 05-20-2011, 07:22 AM
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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.
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post #13 of 30 Old 05-20-2011, 07:33 AM Thread Starter
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im only running a teraflex leveling kit with chopped fenders
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post #14 of 30 Old 05-20-2011, 07:44 AM
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You'll be fine then with 4.52" Backspacing
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post #15 of 30 Old 05-20-2011, 08:11 AM
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Quote:
Originally Posted by jakefister11 View Post
i have question not to take over your thread or anything but what size spacers do i need to get for a 3 inch lift and do i need it on all 4 tires or just the front sorry im really new to all this
I don't think you would need spacers if you're only doing a lift; that is to say, unless you're getting new tires with that lift and need to push a wider than stock tire out a little more to avoid rubbing on suspension components.

There are different kinds of spacers.

Coil spacers, add a little extra boost in height by increasing the vertical height of your suspension spring - A/K/A the budget boost.

Wheel adapters are metal spacers that bolt onto your existing lugs and provide a new set of lugs that you bolt your wheel onto. They should ALWAYS be installed using loctite on the factory lugs so that the spacer is then permanently installed.

Wheel Spacers are just that, a metal spacer placed over your existing lugs that retain your stock lugs. They're not ideal since you're actually reducing the amount of lug you can bolt on to. They're not safe and really shouldn't be used. Ever.

Although most of us know that when we're discussing "wheel spacers", we're really talking about adapters, some folks might not so I thought I would just toss this completely unsolicited advice on the pile.
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post #16 of 30 Old 05-20-2011, 08:12 AM
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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.


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post #17 of 30 Old 05-20-2011, 08:36 AM Thread Starter
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thanks for the help, i am ordering today then.
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post #18 of 30 Old 05-20-2011, 09:30 AM
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Quote:
Originally Posted by jeeperjkj View Post
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
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post #19 of 30 Old 05-20-2011, 09:50 AM
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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?
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post #20 of 30 Old 05-20-2011, 11:00 AM
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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.
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post #21 of 30 Old 05-20-2011, 11:11 AM
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Quote:
Originally Posted by jrider View Post
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.
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post #22 of 30 Old 05-20-2011, 11:43 AM
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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.
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post #23 of 30 Old 05-20-2011, 11:52 AM
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Quote:
Originally Posted by PhilD View Post
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

?

Last edited by Panamon Creel; 05-20-2011 at 11:59 AM.
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post #24 of 30 Old 05-20-2011, 12:29 PM
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Quote:
Originally Posted by Panamon Creel View Post
Clearance to the rim Yes but to the tire?
The edge of tire and and edge of rim are directly related.


Quote:
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
?
Or you could just say 4.5" backspacing or less and be done with it

For the purposes of clearance backspacing is of more use. All you do with offset is work out the backspacing anyway and you need to involve rim width. You can say that 4.5" or less backspacing is good, there is no offset figure or even a range that you can say is good as it depends on rim width. Much easier to talk in terms of backspacing.
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post #25 of 30 Old 05-20-2011, 02:55 PM
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Quote:
Originally Posted by PhilD View Post
The edge of tire and and edge of rim are directly related.
But is the thickness between the inner bead seat and inner Flange always the same or can it vary with the wheel design?
Also same width tire overhang over the rim edge will vary with rim width.

Quote:
Originally Posted by PhilD View Post
Or you could just say 4.5" backspacing or less and be done with it
At what rim width?


Quote:
Originally Posted by PhilD View Post
For the purposes of clearance backspacing is of more use. All you do with offset is work out the backspacing anyway and you need to involve rim width. You can say that 4.5" or less backspacing is good, there is no offset figure or even a range that you can say is good as it depends on rim width. Much easier to talk in terms of backspacing.
I beg to differ, You don't really need rim width or backspacing when using offset.
With offset I just need to know tire width and one can relatively quickly calculate the approx. inboard position of the tire from the Hub surface and compare it to stock.
e.g. stock 255/75R17 (32"), Moab 17X7.5" , +44.45mm offset
255 / 2 + 44.45 = 171.95mm Approx. Tire inboard position from Hub.

now 315/75R16 (35") on a 16X8, 16X8.5, 16X...., 0mm offset rim
315 / 2 +0 = 157.95mm Approx. Tire inboard position from Hub so about 14mm more clearance inboard vs. stock which should be just OK with the 3" larger diameter tire but safer would be a -10 or -12 offset which would give about 24 or 26mm more clearance respectively (315 / 2 - 10 = 147.5mm).

IMO not so simple and more variables involved when using backspacing but feel free to prove me wrong in that regard
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