Hello,

I'm looking to get some new wheels and tires for my 2014 unlimited. I like the Ballistic Jesters 17x9. That size with the bolt pattern for a Jeep JK is offered with an offset of a positive 12 or a negative 12. I don't want the tires to stick out too far past the fenders but I don't want them to be "tucked in" either. Any help with choosing the correct offset would be greatly appreciated.

Thx

 

A zero offset on a 9" wheel is a bs of 4.5" 12mm is basiclly 1/2" so you can go with a 5" or 4" in that wheel. Without knowing what size tire you are running it is impossible to answer your question. Just know the bigger the tire you run the lower your back spacing neds to be.

 

Here is a link to a calculator where you can convert offset to backspacing.

CCW - Complete Custom Wheel // Technical - Offset Backspacing Converter

+12 offset on a 9" rim converts to 5.47" backspacing.
-12 offset converts to 4.53 backspacing.

The factory backspacing is 6.25" IIRC.

So if you stay with the factory size tire with regards to diameter and width,
the +12 offset will move your wheels out approximately .75".
the -12 offset will move your wheels out approximately 1.75".

 

I think you need to check your math.

 

lol...dirtman. What'd I do wrong?

Are the factory rims a different width?

 

I looked at that calculator and it says what you said.
I see a 9" wheel would have a bs of 4.5" at a zero offset or the center of the wheel. A 12mm +- offset should move the bs approximatly 1/2" either way ending up with a bs of 5" or 4".
Something does not add up right.

 

I thought the same thing but checked two different sites. I thought 0 offset was the centerline of the rim. I'll have to keep looking.

OP, ignore post 2.

Edit: Maybe because it is taking into consideration the flange. Still researching.

Edit again: I can't find why the calculators I checked are converting that way so I give up.

 

Okay let's try this again.

For lack of a better term, let's call the rim width minus the backspacing the frontspacing, which is the distance from the mounting surface to the outside bead seat.

If factory backspacing is 6.25"and you are staying with the same diameter and width tire, then...

if your current rims are 7" wide, then the current frontspacing would be .75" (7-6.25).
if your current rims are 8" wide, then the current frontspacing would be 1.75" (8-6.25).
if your current rims are 9" wide, then the current frontspacing would be 2.75" (9-6.25).

So if you go with a 9" rim with +12 offset then you would have 5.5" of backspacing. 5.5" of backspacing on a 9" rim would give you 3.5" (9-5.5) of frontspacing.

Therefore,

if your current rims are 7", then your rims (and tires) would move out 2.75" (3.5"-.75").
If your current rims are 8" wide, your rims would move out 1.75" (3.5"-1.75).
for 9" rims, your rims would move out .75" (3.5"-2.75).


So if you go with a 9" rim with -12 offset then you would have 4.5" of backspacing. 4.5" of backspacing on a 9" rim would give you 4.5" (9-4.5) of frontspacing.

Therefore,

if your current rims are 7", then your rims (and tires) would move out 3.75" (4.5"-.75").
If your current rims are 8" wide, your rims would move out 2.75" (4.5"-1.75).
for 9" rims, your rims would move out 1.75" (4.5"-2.75).

Edit: Calculations changed to include flange in backspacing.

 

So apparently the rim width is measured from the bead seats. The industry standard for flanges is .5". So therefore post 3 was correct.