Speedometers are charts that take too much space for little information. Avoid using them.
If you have to use them, make sure its scale is something meaningful. If I do use them, the scale almost always is from 0% to 100%.
Alternatively, you could use them if they are a good metaphor for the information. Let's say you are making a F1 app. So you could use speedometers to display Max or Avg speeds.
