Yes and i learned the hard way. I had a 95 v6 with 15 inch wheels. I put on a set of 17 inch GT rims from a 95 GT. Well i was going 61 i thought in a 55 and the officer said i was going 65. This is when i figured out that the speedo was off and other confirmed this would do it. I dont know how u correct it on the newer stangs, probably with a reflash of the computer i would say but dont know for sure.