I have read them all, Still need help - JKowners.com : Jeep Wrangler JK Forum
 
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post #1 of 9 Old 09-07-2012, 03:25 PM Thread Starter
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I have read them all, Still need help

I see a lot of good examples of wheels size, tire size and off set just not the one I'm trying to do. I really hate to ask but here goes.
I don't really understand the off set back spacing even no I have read 500 posts. I get some of it but not all of it. And no I'm not a dummy or I don't think I'm slow for a better word just new to all this. Newbe =dummy maybe.

My new wheels are 8" wide and have a off set of 0 the tires I want to put on them are 285/70r/17 don't call them pizza cutters.
My Jeep has a 2 " lift. Can I run this with out any rubbing without spacers????
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post #2 of 9 Old 09-07-2012, 03:42 PM
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Yeah you'll be fine, 0 offset is generally good up to 315/70R17 but there you may get rubbing at steering lock with tires that run large in their specified size.


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post #3 of 9 Old 09-08-2012, 06:36 AM
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your fitment is good.....backspacing and offset are easy. both are the same obviously...just old school versus new school.

backspacing is calculated from the back of the mounting pad to the back lip of the wheel. easy.

offset is a little different. take any wheel out there and add one inch to the width of what it is advertised......9"....add 1. makes it 10. 0mm offset is dead center on that width. 5" backspacing. every 12mm to the positive or negative is half an inch. -12mm means you subtract .5 and that moves the mounting pad back towards the back lip.

'12 JKU, 3.5", D44 front swap w/ OX & 5.13s. CMM & Rimz One Built.
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post #4 of 9 Old 09-08-2012, 07:09 AM
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Quote:
Originally Posted by AppSt59Dave View Post
your fitment is good.....backspacing and offset are easy. both are the same obviously...just old school versus new school.

backspacing is calculated from the back of the mounting pad to the back lip of the wheel. easy.

offset is a little different. take any wheel out there and add one inch to the width of what it is advertised......9"....add 1. makes it 10. 0mm offset is dead center on that width. 5" backspacing. every 12mm to the positive or negative is half an inch. -12mm means you subtract .5 and that moves the mounting pad back towards the back lip.
Nicely said Dave!

I have laid the math out a few times and when I re-read it I think it looks like hieroglyphics. Lol


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post #5 of 9 Old 09-08-2012, 07:39 AM
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Originally Posted by RiverCityOffroad View Post
Nicely said Dave!

I have laid the math out a few times and when I re-read it I think it looks like hieroglyphics. Lol
no kidding. im glad its what i do everyday...at the end of each day my head is still rolling smoke out my ears dealing with people and the same questions over and over.

at least its not anything mechanical...id mess that up way to quick. sure, that tranny and motor will work together...BOOM!

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post #6 of 9 Old 09-08-2012, 01:50 PM
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Also worth noting is that backspace is an absolute value, while offset is dependent on wheel width.

Two wheels might have a 4.5" backspace, but a different offset if they are different widths.
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post #7 of 9 Old 09-08-2012, 03:14 PM Thread Starter
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Quote:
Originally Posted by AppSt59Dave View Post
your fitment is good.....backspacing and offset are easy. both are the same obviously...just old school versus new school.

backspacing is calculated from the back of the mounting pad to the back lip of the wheel. easy.

offset is a little different. take any wheel out there and add one inch to the width of what it is advertised......9"....add 1. makes it 10. 0mm offset is dead center on that width. 5" backspacing. every 12mm to the positive or negative is half an inch. -12mm means you subtract .5 and that moves the mounting pad back towards the back lip.
I copied this, now it makes since to me thank you
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post #8 of 9 Old 09-08-2012, 04:09 PM
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Tin floor. 5 years in college, degree in finance and one other one I can't remember.....this is the smartest thing I can currently remember

'12 JKU, 3.5", D44 front swap w/ OX & 5.13s. CMM & Rimz One Built.
Sponsored by Rigid Industries & Method Race Wheels

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post #9 of 9 Old 09-10-2012, 08:10 AM
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Quote:
Originally Posted by gobstopper View Post
Also worth noting is that backspace is an absolute value, while offset is dependent on wheel width.

Two wheels might have a 4.5" backspace, but a different offset if they are different widths.
Well that depends the way how you look at it, true a 0mm offset 8" vs. 9" wheel will have different backspacing but if you mount an equal width tire on each wheel you'll get about the same distance between the inner tire wall to the mounting flange (WMS).
With equal backspacing on 8"and 9" wheel and same width tire mounted on each you'd get more distance between WMS and inner tire wall on the narrower wheel.
Therefore for inner tire wall interference, which is most of the time the issue on our Jeeps, offset is better since it is stable across different wheel width at a given tire width. Backspacing is the better measurement if looking at rim interference issues to components like brake caliber, TREs,... etc. since the inner wheel flange location will be about equal with same backspacing on different wheel width.
The most difficult part is to wrap ones mind around how each offset and backspacing works and how to apply each practically. Problem is most only know one of the two and dismiss the other one out of hand without really knowing why.


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