The Backspacing Thread - Great Lakes XJ

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Date: Jul 31, 2008

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I had a tire/wheel thread that was a poll at one time, and I kept finding wheel designs I liked a lot and it sort of evolved into me going postwhore with pictures of wheels. So, I thought I'd make a useful thread on the subject of backspacing. I don't know a whole lot about it, besides looking at the wheel from the front (as if it were to roll at you) offset is how far over the tire is from the mounting flange (where the lugs go through). Me- with ever increasing fuel prices, money needed for other things, and crap like that, I'm thinking a 2" lift and 31s (with the right rims so there's no rubbing) is about all I'll do. It'll get me 3" of lift over stock though (1" from the tire (vehicle lift is half of increase of tire diameter) and 2" from the lift). I intend on keeping 15" rims since tire sidewall is a good thing, and not going with a tire wider than about 10 inches (I think that's the standard width of a 31" BFG AT). For this purpose, and others like me (I'm sure you're out there) I wonder what backspacing we'll want to prevent rubbing on the LCAs. I think a little more bumpstop or minor fender trimming (about an inch or so) would be good for those of us with minimal lifts and larger tires. Going the next step up to a slightly larger lift, as I would want in a more all-terrain-assault-vehicle type XJ, here's what Lead Not Follow (Adam) suggested in the wheel thread I posted a while ago... Your going to want a 15x8 wheel. Do not even mess with 7" wide rims as if you ever want to go with a 12.5" tire down the road you'll be kicking yourself for doing so with the 7" wide rims. Your going to want an offset (backspacing) of 4.5"-3.5". The lower the number (closer to 0) the farther they will stick out. Once again if you think you'll ever run a larger tire I'd go closer to the 3.5" than the 4.5" for added clearance. My opinion is to find a rim that's 4" to 3.75" in BS on a 15x8 rim. What's your combo (lift+trimming+tires+backspacing= interference or no?) This is an attempt at creating a database of sorts to find the backspacing needed for no rubbing in a wide assortment of XJs, since some want bigger tires and no lift and no trimming, others want to be high as a kite, get happy with a sawzall, and get tires that will fill those newfound voids, and others (like Lead) a medium lift for a low center of gravity and the biggest shoes that'll fit without interference. Thanks, Matt, and anyone else who finds this thread useful __________________ My Fleet 1996 XJ "Snowball"- 3.5" lift, bunch of little mods. I hate pegleg rear axles! 1974 AMC Javelin "Jade Grenade"- 360v8, 4sp, green inside and out. Underfunded Project. 2009 Kawsaki Vulan 900 "Rocket III"- Summer DD

dogwonk

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Date: Jul 31, 2008

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Okay, here are my specs:

I am running 33" tires that are 12.5" wide on a 15" rim. (They are Maxxis Bighorns, by the way...

)
My backspacing is 4".

All of this on a 3.5" Rubicon Express SuperFlex Lift Kit (which actually nets about 4-4.5" of lift).

I have MINIMAL trimming. I still have my stock fender flares. If you look at my pictures you will see that the flare has been trimmed. We trimmed a little of the actual metal (lower rocker/fender, right in front of the door) that was exposed after trimming the flare.

At full lock I occasionally rub on the inner wheel well liner, but that is partially because it is starting to come loose.

Please remember that my tires are 12.5" wide. If you run 31" tires they will more than likely be 10.5" wide.

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Motion Offroad

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With a 2" lift on the XJ and 31x10.5" tires your going to want a rim with 4" backspacing. I would also run a 8" wide rim so if in the future you want to go larger (tires) you do not have to get new rims.

Also remember, that backspacing is directly related to the width of the rim. A 7" wide rim with 4" of BS and a 8" wide rim with 4" of BS will NOT sit the same.

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89eliminator

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im runnin 33x10.5 BFGs on 15in rims. ProComp rims with i believe 3.75" of backspacing. I have the front inner fenders and the front of the flares trimmed and they still rub a little when fully stuffed while turning. They also rub the lower control arms when flexed and fully steered left or right. oh yeah 6.5in lift __________________

PlayStation

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Very important thread this.

This is my issue. I have about 2.5" of lift on my XJ. I am now planning on buying new tires as i have been using the stock xj tires. however i intend to use the stock 15" rims.

I need advise here. Which suitable tire size can i use without doing any other modification to the XJ. That means no fender trimming and no backspacing. YES, NO BACKSPACING! Remember this is 2.5" lift Xj without any other suspension modification whatsoever.

Related issue..... I have noticed that since i lifted the xj the front suspension link rubbers keep on getting damaged/wearing out very fast. am thinking longer links might be necessary. my intention is to modify the stock links by lengthening them with an added piece cut off from another link. that is use 2 links to make one longer link. question is what would be the recommended link length for a 2.5" lift?

Thx in advance.

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Chris99XJ

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I have a 4.5 inch lift. 32'' tire's, I think wheels are 15'' x 8 or 10'' 's , i dont know. i think a 4.5 inch back space. what do i need for 33'' or 35'' tires ?????????????????????????????? __________________ 1999 XJ SPORT, 4.5'' LIFT, 32'' X 11.50'' TIRE'S " IF IT AINT RUFF IT AINT ME ! "

LEAD_NOT_FOLLOW

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Chris99XJ wrote:
I have a 4.5 inch lift.
32'' tire's, I think wheels are 15'' x 8 or 10'' 's , i dont know.
i think a 4.5 inch back space.
what do i need for 33'' or 35'' tires ??????????????????????????????

What width on the 33 or 35's as that is key to a good answer. I'm going to assume you want a 12.5" tire correct?

With a 12.5" tire you want either 4" or 3.75" BS on a 8" wide tire. It will vary on what rims you go with and what backspace they are available in.

Just for referance Chris, this is what a 35x12.5x15 looks on a 15x8 rim with 3.75 backspacing as far as sticking out goes.

Here is a good shot showing what they look like. Once again my XJ (with roof rack) with the combo above. Rebecca's XJ is on my old 31x10.5x15 on a 15x8 rim with 3.5" backspacing for referance.

Personally (and this is just my opinion) since you have the bushwackers I'd run 3.5-3.75" backspacing with a 12.5" wide tire to get the right look. It will put your tire just about flush (if not just a smidge out further) than the BW's are. This will allow you to hit your tire on the trail and not the BW's to rip them off.

-- Edited by LEAD_NOT_FOLLOW at 21:45, 2008-08-01

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Chris99XJ

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Because of the flares, thats what i am looking for, Thanks for the info __________________ 1999 XJ SPORT, 4.5'' LIFT, 32'' X 11.50'' TIRE'S " IF IT AINT RUFF IT AINT ME ! "

Topic: The Backspacing Thread