I have a 1990 R32 GTS-T and i currently have 215/45/17 in the front and 245/45/17 in the rear. When I go on the highway, the speedometer will read around 120km/h but in reality I am only going 107km/h. Is there a way to fix that? Also if i'm going 140km/h, it is 120km/h in reality. Any input is highly appreciated. Thanks in advance.