OK I am looking to buy some new rims for my 98 Ex. Sport (4.0L , SOHC, 4 wheel drive, A.B.S.). My explorer has 17" rims stock. I am considering switching to 18" rims with a lower profile tire (do not want to throw the speedometer off or throw an ABS light). My question is, what size tire do I switch to keep the diameter of the entire set-up the same? Thanks for looking.