Okay so I have a 2007 f150 4x4. I currently have a 6 inch RCX kit in the garage. I love my Fierce attitude tires and want another set. They don't make 35x12.50r18 but do make a 325/65/18 which is about a 35x13.50. So my question is what size offset will I need for it to not rub the a arm? -12 for a 18x9 and -24 for a 18x10? Any response would be highly appreciated.

 

Hopefully someone will correct me if wrong but im guessing -64.

 

Guess I should explain how I made my guess & hopefully it will make sense.

Difference between 9in 10in rim -12mm which basically 1/2in cause tire sticks off both sides of rim.
You need 13 1/2in so extra 3 1/2in in addition to 10in with 24mm so 3 1/2 x 12 = 40mm + 24mm = 64mm