if you are using 225 then itll be either an 8 or 8.5" wide rim i presume, rondells are 8.5 and et of 18, if for example you used an 8" rim you would need an et of 12 to get it to extend the same amount as the rondell but the inner face would be 12mm more clearance, if you go for an et higher than 18-20 you could end up with clearance issues for your brakes and shocks