just leave the 18" rims. they're going to grip better than oem. yea take the floormates out, take jack, spare out. u should be good to go. oh btw. it is required to take out the floormates. if u become a hardcore autox'er u'll eventually get some 15" lightweight rims with falken azenis. oh if u didnt know already u're classed in STS. for more info go visit the autox forum here or at honda-tech