Was on track today and noticed a huge variance between the indicated speed and what my Qstarz GPS as well as my Dashcam registered.
Speedo showed over 160 MPH, GPS shows ~146-148 MPH.
Running factory wheels and tires and even if I weren't, >10% difference is huge.

I googled a post on Gallardos having 10% variance as normal/within spec, but this is kinda off putting for me. Any way to calibrate the reading on our cars?