Ok, I searched for my issue and found everything but my answer to my issue, lol. First off I will say I'm basing my correct speed off my nav which is connected to the vehicle speed sensor/signal. I have 35"(315/70/17) Duratrac tires on 17" rims, and I bought a Superchips Flashcal.
Prior to the Superchips my speedo would say 55mph and I was really going 59-60mph. Fast forward to my buying the Superchips and changing tire size to 35". Now my issue is exact opposite, if I'm going 55mph on speedo, I'm actually going 50-51mph and it gets worse the faster I go, if I'm up to about 75mph on speedo, I'm actually only at 67-68mph.
Should mention it's a 15 Sport
Last edited by Shawn1112; 08-13-2015 at 03:57 PM.