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backspacing and rim size?

282K views 175 replies 120 participants last post by  20Jeep15! 
#1 ·
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.
 
#2 ·
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...
 
#17 ·
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?
 
#26 ·
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.
 
#9 ·
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?

Joe
 
#10 ·
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.
 
#12 ·
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
 
#14 ·
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.
 
#15 ·
Roger!

I just posted an answer for you, under "JK Jeep Wrangler Forum", Topic titled, "please make me feel better about my wheels". I hope my response helps you there!

Cheers!

BB
 
#19 ·
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.
 
#22 ·
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.
 
#23 ·
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).
 
#27 ·
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. :)
 
#28 ·
Sticks said:
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?
 
#30 ·
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.
 
#31 ·
It I was you, I'd order 15x8s with 4" b.s. just so that it will accommodate 33x12.50's later when you decide 31x10.5 isn't big enough. :)
 
#33 ·
I'm new to this forum and haven't found the answer to a question I have. I have a 97 Wrangler with a 4" lift, 33 x 12.5 Super Swampers with a 4 cyl. It's dog slow on the road! I bought the Jeep this way and it was intended to be used as a hunting vehicle to get into the back woods down two tracks. Now I need this more as a primary source of transportation. I intend to go to stock rims and 31 x 10.5-15 all terrain tires. Can anyone offer any advise on how this will perform on the highway, as far as acceleration and crusing speed? I don't want to go too small on the tires because of the lift.
 
#36 ·
wheel offset

still not clear on offset and backspace , I have a 2010 unlimited looking to buy mb wheels chaos 5 16x8 with -6 offset and put either yokohama geolander 245/70/16 or bf goodrich lt t/a 235/75/16 are either tires good for this wheel and will this put any extra wear on bearings , I have no idea how fat this will come out towards fenders
 
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