g'eep09jk

Could anybody give me some info on how to determine what offset or backspace I need when purchasing wheels??? I am looking at buying a set of XD Monster wheels which are 18x9. I am gonna put a set of Nitto Mud Grapplers 35x12.5. I have been reading up a little on backspacing/offset and before I spend $2K on wheels/tires, I woud like to make sure I am getting the right size...

Any imfo would be greatly appreciated!! Also, if you have any feedback on the wheels/tires in general, I'd appreciate that as well.

Thanks for your help!

JayhawkJeep

This should give you a good start.

https://www.jk-forum.com/forums/show...74&postcount=3

spinlock

It's very simple. Backspacing is the distance from the back of the rim to the mounting face and offset is the distance from the centerline of the rim to the mounting face. Therefore, backspacing is always positive, unless you live in a virtual world, and offset can be positive (outboard of centerline) or negative (inboard of centerline).

Backspacing determines wheel clearance along the axis of the axle and track width and offset determines axle loading, scrub radius, etc.

g'eep09jk

That makes sense. Thanks! Now how do I determine the backspace needed for the wheels/tires I am looking at. Is there some kind of formula??

I would like the minimum backspace to fit the wheels/tires. Any help with determining this? I have a 2.5" Rubicon Exress lift and I trimmed the rear fender flares. I have yet to trim the front flares, but I think I may have to when I get the wheels/tires...

Thanks for your help so for. I understand the backspace and offset a little better now.

g'eep09jk

Thanks for the link. I am still trying to figure out how I calculate it for these wheels/tires for my Jeep...

ARM2004

I have the 35x12.50 nitto mud grapplers on a 17x9 rim with 5on5 lug spacing with 4.5" of backspacing and i have no problems with rubbing and would do it again if given the choice to do it again. As long as you buy a rim with atleast 4.5" of backspacing your good, you could probably go with 4.25" or 4" but that will make the tire stick out past the wheel flares that much more and probably isnt neccessary.

TEEJ

I'm not sure why after reading the thread you still don't know how to do it, but, it could be that there were a lot of words and pictures?

As you are really just trying to figure out what backspacing to get, the answer is 4.5 - 4.75"


If you want to know WHY -

I suggest that you consider what backspacing is....and go from there.

Backspacing simply describes how deep the dish on the brake side will be, and is primarily used as a predictor of clearance.

MORE BS means the wheel is tucked tighter into the wheel well (The dish facing the brakes is deeper).

LESS BS means the wheel protrudes outboard more.

The stock rims have a lot of BS, 6.25", and can easily fit stock 255 mm wide tires.

The conversion is 25.4 millimeters (mm) per inch.

That means that a stock 255 mm tire is ~ 10" wide.

You are planning on running 12.5" wide tires.

These will protrude INBOARD (Towards the frame) by ~ 1.25"

So, to compensate, you want to move them OUTBOARD by ~ 1.25", to get your clearance back.

That yields a new BS of 5" (6.25" - 1.25" = 5.0")

Now, as the tire now swings in a wider arc due to the wider track, you add a little more as a buffer zone.

Most people use an extra 1/4" - 1/2" or so for that.

This yields the common 4.5" - 4.75" BS most people running 12.5" wide tires use.

g'eep09jk

Excellent!! That's what I wanted to hear. So the 4.5" of backspacing is a good fit with those tires huh?? How do you like the mud grapplers. I've read up on the reviews and everyone had good things to say about them. Are they as loud as I understand them to be? It's an aggressive looking tire and a buddy of mine can get me a set for less than $200 a tire, so as of now it's a no-brainer for me.

Do you know what the backspacing is on the stock Rubi wheels? That's what I have on there currently. I thought I had a 4.5" backspace right now. I figured with wider tires, I may need less than 4.5". Let me know.

Thanks for your help!

TEEJ

You have 6.25" of BS




PS -

Q: What back spacing will I need on my wheels in order to clear 12.50 wide tires?

A: I would recommend that you do not exceed 4.75" of back spacing and even at that, you may still have some minor rubbing up front at a full turn. Also, I would recommend that you do not go any less than 3.75" as anything less would cause your tires to stick out very far past the fender flares. Any back spacing within this range should work out great.




Q: What are all the factory wheels that are available for the JK?

A:Factory wheel type and sizes listed below:

X Standard
Painted Steel - Size 16 x 7.0

X Optional
Painted Cast-Aluminum - Size 16 x 7.0 (2007)
Painted Cast-Aluminum - Size 17 x 7.5 (2008)

Sahara Standard
Painted Cast-Aluminum - Size 17 x 7.5

Sahara Optional
Painted Cast-Aluminum - Size 18 x 7.5

Rubicon Standard
Machined Cast-Aluminum - Size 17 x 7.5

Backspacing on all factory wheels is 6.25"

g'eep09jk

Thanks TEEJ. I think I'm with you now. Yeah, I missed that earlier. Thanks for your help buddy!