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Old 06-11-2009, 11:57 AM   #1
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backspacing and rim size?

dumb ? but what is back spacing and If I plan to get new rims for my 06' TJ

what is the bolt pattern and would 16" rims give me any benefit over 15" rims
thanks ton.

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Old 06-11-2009, 12:27 PM   #2
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Backspacing is the distance between the wheel's very back edge and the flat part of the wheel that fits up against the brake rotor. The more backspacing, the more the wheel is positioned into the wheel well. The tire width dictates the amount of backspacing required. If you have too much backspacing, the tire is positioned too far into the wheel well and its inside sidewall can rub. Insufficient backspacing and the wheel protrudes out too far and can look like a skate board.

The bolt pattern required for a TJ is 5x4.5" and there's no real benefit to 16" except for the minor fact that the current style is for bigger wheels. But you'll find a larger assortment of Jeep type (offroad) tires for 15" wheels than you will for 16" and they'll be cheaper too. If you offroad and air your tires down, I advise a 15x8 wheel for any size tire up to 37x12.50, I'd only go for a 15x10 wheel if the tire was 13" or wider.

Here's how the backspacing is actually measured...
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Old 06-12-2009, 11:34 AM   #3
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thanks a ton I feel like a big dummy when it comes to this.
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Old 06-12-2009, 11:44 AM   #4
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thanks a ton I feel like a big dummy when it comes to this.
Don't! This a common question.



I stickied this thread for faster reference. Thanks Jerry B.
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Old 06-23-2009, 08:26 AM   #5
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Useful info. But what about the offset? I have heard many people talking about "negative" offset, when talking about rims? Isn't it somehow opposite to the backspace?
Sorry if this is a dumb question.
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Old 06-29-2009, 01:53 AM   #6
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Offset and backspsce are related... negative offset moves the tire out and the backspace gets smaller, positve offset moves the wheel in and the backspace gets bigger...
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Old 06-29-2009, 07:18 AM   #7
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Quote:
Originally Posted by amicus View Post
Offset and backspsce are related... negative offset moves the tire out and the backspace gets smaller, positve offset moves the wheel in and the backspace gets bigger...
Thanks a lot.

How is it measured?
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Old 07-19-2009, 11:08 PM   #8
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Hello, i'm running a 35" tire, what should my backspacing be?
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Old 09-16-2009, 01:49 AM   #9
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I just purchased an 06 Rubicon. I plan for 33x12.5 tires. My last ride had this size tire with ten inch wide wheels forever and had no issues. What is the benefit for an eight inch wide wheel, and wouldn't that cause the tread to 'rainbow' in the cross section?

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Old 09-19-2009, 07:57 AM   #10
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I run 33x12.50 on a 8" rim with 2.5 inch back spacing,with 24lbs air on road and 12lbs offroad. You can get a little more height out of a 8" wheel versus a 10" wheel.
I went with the 8" because If I ran 10" with a 2.5" offset they stick out too much.
I am old enough now I do not need the problems with the cops.
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Old 11-01-2009, 04:58 PM   #11
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2001 Sahara w/3" Lift & 33x12.50x15 MT Baja Claws

Can anyone recommend a less agressive road tire? Just bought this Jeep and the road noise is horrible.

I already experienced the Death Wobble. Does not appear that anyone of the tires are balanced.
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Old 11-01-2009, 11:33 PM   #12
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Goodyear duratracs. BfGoodrich KM2s, Mickey thompson MTZ, Goodyear MT/R with Kevlar

All those i have heard to be very quiet for what they are. I can vouch for the duratracs..they arent an M/t but more of a hybrid between a/t and m/t
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Old 12-29-2009, 02:30 PM   #13
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Can anyone recommend a less agressive road tire? Just bought this Jeep and the road noise is horrible.

I already experienced the Death Wobble. Does not appear that anyone of the tires are balanced.
Cooper st's cant make up my mind between st's and bfg a/t's ko for my dd
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Old 01-16-2010, 05:52 PM   #14
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Currently I have stock 17x7.5 rims and supposedly they have 6.25 backspacing and 44.45 mm offset. I upgraded tires to 285/70/17 tires. I put 1.5 inch wheel spacers on there too. My question is I want the tires to stick out another 1 to 2 inches. They dont stick out even with the spacers. Is that because of the 6.25 backspacing? Do I need to get 17x8 or 17x9 rims and less offset? If so what would be appropriate? I am so confused.
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Old 01-17-2010, 02:05 AM   #15
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Originally Posted by rogerlillo View Post
Currently I have stock 17x7.5 rims and supposedly they have 6.25 backspacing and 44.45 mm offset. I upgraded tires to 285/70/17 tires. I put 1.5 inch wheel spacers on there too. My question is I want the tires to stick out another 1 to 2 inches. They dont stick out even with the spacers. Is that because of the 6.25 backspacing? Do I need to get 17x8 or 17x9 rims and less offset? If so what would be appropriate? I am so confused.
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Old 01-21-2010, 05:48 PM   #16
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Cooper st's cant make up my mind between st's and bfg a/t's ko for my dd
i like the coopers weather they are the st's or the stt's i like both. them kos last a while too.

i put stt's on my wifes truck they have gotten louder but i like em, and weve gotten good milage out of for a m/t.
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Old 01-31-2010, 03:29 AM   #17
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Backspacing is the distance between the wheel's very back edge and the flat part of the wheel that fits up against the brake rotor. The more backspacing, the more the wheel is positioned into the wheel well. The tire width dictates the amount of backspacing required. If you have too much backspacing, the tire is positioned too far into the wheel well and its inside sidewall can rub. Insufficient backspacing and the wheel protrudes out too far and can look like a skate board.

The bolt pattern required for a TJ is 5x4.5" and there's no real benefit to 16" except for the minor fact that the current style is for bigger wheels. But you'll find a larger assortment of Jeep type (offroad) tires for 15" wheels than you will for 16" and they'll be cheaper too. If you offroad and air your tires down, I advise a 15x8 wheel for any size tire up to 37x12.50, I'd only go for a 15x10 wheel if the tire was 13" or wider.

Here's how the backspacing is actually measured...
So apparently I have a lot to learn yet. How are rims measured compared to tires, because my feeble mind doesn't understand how your tires can be wider than the rims. Either I'm missing something, or I'm missing something else. Anyone care to shed some light on this for me?
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Old 01-31-2010, 02:26 PM   #18
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So apparently I have a lot to learn yet. How are rims measured compared to tires, because my feeble mind doesn't understand how your tires can be wider than the rims. Either I'm missing something, or I'm missing something else. Anyone care to shed some light on this for me?
Because if you tire is as narrow as your rim, it will not stay put on the rim. There has to be some friction/pressure/resistance... ( I don't know the word) to keep the tire seated on the wheel. You can squeeze a wide tire on a narrow rim, it just makes the sidewall bulge more than a bit wider rim. However there are limits to how narrow you can go too. Any tire site will tell you the recommended rim width for any given tire. If you go out and look at any car, the tires are never as narrow as the wheel, there will be some bulge.
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Old 03-11-2010, 09:44 PM   #19
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I would shy away from the Cooper Tires till the get over their recall situation. The Interco Trxus M/T is supposed to be an awesome tire. Aggressive yet quiet, & great in snow,mud, wet road traction,Rock, If you want something less aggressive but still great reviews is the General Grabber AT2. Just check out the reviews on Tirerack.com, I've got the BFG-A/T KO's they're ok for most conditions but they suck on wet roads. I won't be getting them again.
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Old 05-18-2010, 06:37 PM   #20
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Wheel Back space

I have an 05 TJ Unlimited with a 2" lift, can any one tell me the back space number I will need for new wheels, I am looking to put 32X11.50 on 15x8 wheels.
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Old 05-18-2010, 09:09 PM   #21
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You need 4.5" backspacing or less for a TJ with 11.5's
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Old 06-17-2010, 01:10 PM   #22
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ok I have a yj and want to go to a 8" rim and would like for it not to stick out, so I'm wondering what back spacing do I need. I might go to a 10 30 or or 9 30. Right now I have Pro Comp Mudders 12.5 33.5 on 10 or 12" baja rims that stick way out. trying to make it more road friendly.
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Old 07-12-2010, 05:18 AM   #23
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Back spacing and offset are critical to bearing life as well. OEM wheels and recommended tires are mated to put the center of the load between the inner and outer bearings.

A wheel/tire combo that is too much in either direction will wear out the bearings. I.E. excessive backspacing (sticking out farther than the fender) puts excessive load on the bottom side of the outter bearing, likewise excessive load on the top of the inner bearing. This also equals constant side load on the bearing.

Basically when all is said and done, the center line of the tire should be centered over the hub (between the two bearings).
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Old 07-22-2010, 02:59 PM   #24
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I have a buddy that has a 2002 TJ and wants to put 15x8 rims and 31x11 Thornbirds on it. What back spacing and offset should he get?
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Old 07-22-2010, 06:39 PM   #25
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Offset doesn't really apply to Jeeps. He needs no more than 5" bs, but less would give him more room, I'd say 4.5" would be ideal.
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Old 08-17-2010, 12:20 PM   #26
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Useful info. But what about the offset? I have heard many people talking about "negative" offset, when talking about rims? Isn't it somehow opposite to the backspace?
Sorry if this is a dumb question.
OFFSET= the distance of the mounting surface of the wheel from the center of the wheel.

If the wheel has 1" offset, then the mounting surface is 1" outwards from the center of the wheel.

If the wheel has -1" offset, then the mounting surface is 1" inwards from the center of the wheel.

HTH yo.
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Old 09-04-2010, 10:46 AM   #27
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Adding to what YAHAHA posted, -1" offset on a 10" rim gives you 4" of backspace. A -1" offset on an 8" rim gives you 3" of backspace. (to illustrate the negative offset you asked about) So, offset can and does apply to Jeeps but only as a factor in determining backspace. Keep in mind that offset is usually annotated in mm, not inches so some metric conversion math will be needed too.
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Old 09-06-2010, 10:33 AM   #28
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Originally Posted by Sticks
Back spacing and offset are critical to bearing life as well. OEM wheels and recommended tires are mated to put the center of the load between the inner and outer bearings.

A wheel/tire combo that is too much in either direction will wear out the bearings. I.E. excessive backspacing (sticking out farther than the fender) puts excessive load on the bottom side of the outter bearing, likewise excessive load on the top of the inner bearing. This also equals constant side load on the bearing.

Basically when all is said and done, the center line of the tire should be centered over the hub (between the two bearings).
So if I understand you correctly, my stock wheels/tires (30x9.5R15 on 15x8 5.5BS wheels) should put the centerline of the tire between the bearings. If I go to a 31x10.5R15 on the stock rims it would still be centered but I might get some rub on the inside or on turns (which I can fix to a small extend using washers under the steering stop bolts). But if I go to 32x11.5R15 I know I will need to get wheels with smaller BS which will move the tire centerline further to the outside of the vehicle. This is bad for the bearings but really cannot be avoided with the wider tires due to rub. Correct?
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Old 09-06-2010, 11:09 AM   #29
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So if I understand you correctly, my stock wheels/tires (30x9.5R15 on 15x8 5.5BS wheels) should put the centerline of the tire between the bearings. If I go to a 31x10.5R15 on the stock rims it would still be centered but I might get some rub on the inside or on turns (which I can fix to a small extend using washers under the steering stop bolts). But if I go to 32x11.5R15 I know I will need to get wheels with smaller BS which will move the tire centerline further to the outside of the vehicle. This is bad for the bearings but really cannot be avoided with the wider tires due to rub. Correct?
Yep, you got it. Most 10.5's don't rub stock, it just depends on the actual width of the tire..... Mine never rubbed. But they only measured out to about 9.5"...
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Old 09-19-2010, 04:12 PM   #30
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This is just what I was hoping to find...some folks who knew a whole lot more about this than I do!!!

Here is my question...I want to get new wheels for my '06 TJ since it is tire time also.

I plan to run 31" x 10.5" x 15" tires. What wheel configuration should I order in offset and backspacing?

Thanks.

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