I have 2004 F-150 Lariat with stock 275/65r18 tires on stock rims and just wondering how big of tire i can run without lifting truck or having problems with rubbing, there is a set of 325/65r18 I am looking at and just wanted to know limits

 

i'm running 35x12.50x18 on my 2004 FX4 with only a 2.5" autospring leveling kit. it fits fine with no rubbing and looks great.

 

325mm wide 35" tires will require a leveling kit, and those are a bit wider than recommendations for the factory 7.5" rim (those tires are 13" wide).

 

I agree. A 325mm wide tire is a little too wide for the OEM wheels.