No, not at all. The speed is taken off the rear brake rotor bolts. You will notice a black electrical sensor right next to the rear brake caliper. This is the speedo pickup. You can run whatever gearing you choose, and still have an accurate speedometer. Just, do not change the brake rotor bolts to a non-ferrous metal like titanium (the speedo wont work)
Note: Unlike most other bikes, the Aprilia speedometer is very accurate, even at high speeds.