My '06 with OEM Dunlop D 250's is running 70mph at an indicated 75mph. Two weeks ago I installed the www.speedohealer.com and now have an accurately displaying speedometer. Except for having to remove many body parts/panels the speedohealer is very simple to install, program and use.
Hope this helps!
My 06 speedo is 3 MPH off. It reads 3MPH higher than actual. I testti=his weekly with my GPS - not the one that comes on the bike. at 3000 RPM I am doing 70 MPH. Hope this helps. BTW - It affects your Odo also