I have stock 17 on the 12 rubicon if I go with 285 70 R17 what size of rim offset is needed? To add to this I'm thinking going with the Mamba MX-1 I like them but have seen two jk around town with them already

 

Most likely, the wheel you're looking to get is only available in a few different offsets. Depends a lot on what look you're going for as well. Do you want them to sit within the fender wells, flush with the fenders, or protruding out a bit? Once you know that, then it's a matter doing a little measuring. Any knowledgeable tire shop should be able to help you with that. They can tell you what the maximum backspacing that you can run in and from there, you can choose what's available from the manufacturer that will fit your criteria.

 

Offset uses rim width in the calculation. Positive offsets are tucked into the wheel wells, negative offsets move the tire further out. But again, exactly how far in or out will change depending on the specific rim width. You might find it easier to use one of the online calculators to convert 'offset + rim width' to 'backspace'.

Stock rims are in the 6.25 - 6.00 backspace range. As that number goes down, the rim/tire moves further out of the wheel well. (if stock rim is 6.0 and new rim is 5.0, it sits 1 inch further out - With some variance for width, but it's easier to picture with backspace.) A 33x10.50 is the general recommendation for the largest tire size on stock rims with no rubbing. A 4.50 backspace is a typical recommendation for a 35x12.50. A 3.50 backspace is a typical recommendation for a 37x12.50. The tire size you are looking at might work with stock backspacing, but moving out a bit would probably be the better option. Maybe a 5.5-5.0 backspace? Unless you have plans for larger tires in the future? Or just like a wider stance?

 

I rearly appreciate the response I have a better aspect on things I personally like the wider