Ducati have been a bit clever with the 999, they have put the speed sensor on the rear caliper hanger, It picks up on the rotating disc bolts and then calculates the speed, technically changing my gearing should not have affected my true measured speed, however, changing my disc bolts to titanium ones really caused confusion... My orange light came on and I had no speedo !!! Needless to say the standard bolts went straight back on..