Question

[Sal-XK]

A 17x8 wheel 0 off set means it's has 4.5" back spacing correct?


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[NeilSmith]

I hate math

[07JeepXK]

Well wheels are measured on the inside lip where the bead is...so if its an 8 inch wide wheel its really 9 inches wide....so I would say yes since 4.5 is half is 9 so that would center the inside of the wheel where it mounts being 0 offset...I'm on my phone...when I get to a computer ill confirm this

[Matt]

Yes that's correct... 8" wide wheel with 0 offset = 4.5" backspace.

[Sal-XK]

Cool! next question that should be about the same as 1.5" spacers or a little more? I can link the wheels I'm looking at when I get home to.


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[07JeepXK]

Your stock wheels have 6 inches of back spacing so adding 1.5 inch wheel spacers would make it equal to 4.5 inches of back spacing in theory. The stock wheels are 7.5 inches wide and the new ones are 8 inches so they will stick out a 1/2 inch more. But if your going with 285/70s it will be slightly more then that.

[Sal-XK]

Ok I think that means they will stick out little further then my stock wheels running 1.5" spacers correct? I'm looking at these here
http://www.discounttiredirect.com/direct/findWheelDetail.do?bp=5-127&pc=60397&counter=4&wd=17&rw=8


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[Matt]

Yup, to confirm what was previously posted:

You current setup is 7.5" wide wheels with an effective 4.5" backspace (6" backspace - 1.5" wheel spacers).
So 8" wheels with 4.5" backspace will stick out .5" further than your current setup, without the use of wheel spacer.

[Sal-XK]

Cool thanks guys!


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[Omelet]

Since we are on the subject, I am not good with figuring wheels out either! What would Moabs plus a 1" spacer equal?

[Matt]

Do you know the stock width & offset of the moabs? Or the width & backspace? I can't remember off the top of my head

[07JeepXK]

They are the same width as oem XK wheels.

[Omelet]

It looks like the 17X7.5 Moab wheels are at about 6.25" Backspacing (44.45mm Offset). So with a 1" spacer it is equal to a wheel with 5.25" backspacing and a 1.25" spacer at 5" backspacing?

[07JeepXK]

I found a post on a jeep forum where a member said his wheels are stamped 17x7.5 44.45mm offset on the inside. Thats equal to 6 inches of back spacing. Plug the wheel specs into this calculator.

http://www.rimsntires.com/specs.jsp

[Matt]

Yup yup.... 7.5+1= 8.5" which means the centerline is at 4.25" backspace. 44.45mm offset is 1.75 inches. Add the offset to the centerline position and you get 4.25+1.75= 6" backspace.

So there 7.5" wide with 6" backspace.
1" spacer = 5" effective backspace
1.25" spacer = 4.75" effective backspace

[07JeepXK]

Sometimes I hate math and its just easier to use a tire/wheel calculator...lol

[Matt]

Lol. For stuff like its its quicker to figure it out on my own than finding a calculator.... especially on my phone.

Ya know, its a simple enough equation maybe ill make up a quick excel program to do it and post it so people can download it....

[Holaday07 4.7]

They are the same width as oem XK wheels.

They have a different offset by half an inch. Wont clear the bolt with stock tires and no spacers

[07JeepXK]

They have a different offset by half an inch. Wont clear the bolt with stock tires and no spacers

According to online they are the same as our XK wheels. The reason they Moab wheels require spacers is because they are designed different then our XK wheels and the inside of the wheel hits the brake calipers up front. A 1/4 spacer fixes that issue. Stock tires will clear the ball joint bolt.

[Omelet]

Yup yup.... 7.5+1= 8.5" which means the centerline is at 4.25" backspace. 44.45mm offset is 1.75 inches. Add the offset to the centerline position and you get 4.25+1.75= 6" backspace.

So there 7.5" wide with 6" backspace.
1" spacer = 5" effective backspace
1.25" spacer = 4.75" effective backspace

Thanks Matt! I now understand how this works :) Just picked up a second set of Moabs today!!!

[IamJEEP]

Lol. For stuff like its its quicker to figure it out on my own than finding a calculator.... especially on my phone.

Ya know, its a simple enough equation maybe ill make up a quick excel program to do it and post it so people can download it....

Good idea and then sticky it for others to find easily.

[Matt]

I made the file... just can't upload it. Not sure how else to post it?

[Matt]

See if this works:

http://dl.dropbox.com/u/24438380/Backspace%20and%20Offset%20Wheel%20Conversions.xls