Quick question about backspacing...... - JeepForum.com

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post #1 of 8 Old 07-26-2007, 02:55 PM Thread Starter
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Tj Quick question about backspacing......

Hey guys, I've got stock canyons right now on my TJ with 31x10.5 and I have to problems with them except that at full lock, right or left, they rub. So I've been looking around for sometime now for some black steelies and think I've found a good deal on a pair of 15x7's. I called and asked the guy if he knew what the backspacing was on them and he wasn't sure so he measured from the inner edge of the rim to where the wheel bolts to the hub and it was 4.5. First question, this is the correct way to measure backspacing right? Second question, I have heard, but am not positive, that a 12.5 inch wide tire will fit on a 7 inch wide wheel, is this correct? Last question is can I mount a 12.5 inch wide tire on a wheel with 4.5 inches of backspacing and have it not rub while turning? Thanks for the help guys.

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post #2 of 8 Old 07-26-2007, 02:57 PM
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Can't answer your TJ specific questions on rubbing, but generally a 12.5" wide tire wants an 8" wide rim. The only way to know for sure is to visit the tire manufacturers website and check on their list. It'll display the minimum rim width. Too narrow and it'll bow the tire and cause poor tread wear.

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post #3 of 8 Old 07-26-2007, 03:12 PM
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First, yes, that is the correct way to measure backspacing- basically lie the wheel face down, put a straight edge across the wheel, and measure from the outside of the wheel to the mounting surface.

Second, I'm confused a bit. You are saying that you have 10.50 wide tires, but then are jumping to 12.50. Is this just to make sure that in the future if you go larger that you are ok, or is there a typo in there somewhere?

As far as a 12.50 wide tire, I would go with an 8" wide wheel (which is what most people run...some run 10" wide). With an 8" wide wheel, a 12.50 will fit very well, and allow you to air down lower than a 10" wheel without the chances of blowing a bead as easily. You should be able to run a 12.50 on 4.5" and not have it rub...but you might need to go to 4.75".

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post #4 of 8 Old 07-26-2007, 04:19 PM Thread Starter
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Sorry if I was a bit confusing. I currently am running a 10.5 inch wide tire, and on the stock wheels they rub at full lock. This is the main reason why I want new wheels. However, I am curious about whether or not I would be able to fit a 12.5 inch wide tire on these wheels in the future so that was why I asked about both. I would assume that for now, these 15X7 would be fine for my 31X10.5. After I get my, lift on, I have been thinking about getting some 33X10.5 BFG AT's because they are cost effective, and I would assume don't hit the gas mileage as badly as a 33X12.5. I am not however, set on getting 33X10.5, that's why I was curious about 12.5 inch tires as well. One last question, anyone know of a good inexpensive place, preferably in northern colorado to have my tires mounted on these new wheels assuming I get them? Thanks again guys.

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post #5 of 8 Old 07-26-2007, 04:27 PM
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I have the stock canyons as well with 31x10.5 BFG AT's. I was having rubbing issues until I added a couple of washers to the steering stops.


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post #6 of 8 Old 07-26-2007, 06:14 PM
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12.50's probably would be ok with 4.5" backspacing, however if you could get them with 4" it would be better.
Rubbing when turning full is the least of your worries with too much backspacing - how close the tires are to the upper rear spring perchs is a bigger concern. You don't want to slice up a couple $160 tires. You have to check both sides also because your lift [ trackbar] may be pulling your axle to one side a bit more than the other.

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post #7 of 8 Old 07-26-2007, 09:43 PM
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I got some 1.5" wheel spacers for sale $90 shipped, that would take care of the rub.

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post #8 of 8 Old 07-26-2007, 09:45 PM Thread Starter
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I know I can just add spacers as far as the rubbing goes, but first of all I'm too lazy, second of all, it's only at full lock and I know it so I can avoid it, third of all, I would rather get some wheels with better backspacing so that I can take full advantage of my turning radius. The main that I haven't put my lift on yet is because I have a feeling my stock wheels will make my tires rub on the spring perches.

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