xmarkx:
I am trying to build a speedometer for my bicycle.
You appear to be on the wrong tram. You appear to be counting wheel revolutions, and for a purpose that is incomprehensible. I guess this line of code sums it up quite well
Serial.println("Whell turn times:")
If you really do want to build a bicycle speedometer, there are plenty of examples of fan speed, water flow, engine rpm, even bicycle speedometers, on this forum. They all work much the same way, using an interrupt counter, which is not the way you propose.
Reading reply#8 again would be a rather good idea as well. The speedo I use cost $2.