Tyre speed ratings and up to (maximum) speeds that the car is capable, not necessarily how fast that you drive.
Fitting tyres with a speed index lower to one of the original tyres or that the manufacture recommends is not allowed, and can invalidate your car insurance. Fitting a V rated to a vehicle that should have a W rated. However it is acceptable to tyres with a higher speed index. You can put a V rated tyre on a vehicle that should have a H.
900cc - 1499cc T rated, 1500cc - 1799cc H rated, 1800cc - 2199cc V rated, 2200cc - 2499cc W/Z rated, 2500cc + Y rated
The engines torque has an impact on the speed rating and this will need to be taken in to consideration. It is always advisable to check your tyres or handbook.