Why dont NASCAR race cars have speedometers?

Answer 1

Indy cars do not have speedometer. Instead they measure speed by the Revolutions Per Minute (RPM) of the engine through the use of a tachometer. By using tire diameter, gear ratio's and engine RPM the true speed of the car can be calculated.

Answer 2

It's unnecessary. They are trying to go as fast as they can anyway, and are more concerned with information pertaining to RPM's, temperature & pressure.

Answer 3

No. They only have tachometers.