Custom Y axis range

I am charting a value that will never be lower than 60 and never be higher than 80. The current behaviour is to render a Y axis from 0 to 85. It would be great if I could override the Y axis range to 60-80 because this will make it easier to see changes in values. Right now a change from 85 to 75 is hardly noticeable because it's render on such a large Y axis range.