chart-elements | Chart.js as Polymer Elements | Web Framework library

You do not need to set the attribute auto-fit true. This is for charts that have zooming applied.

You do not need to set the attributes min-value or max-value to get the x-axis to fit automatically. It will do this by default.

The problem might lie in the one part of the chart you didn't give any information about. How is your data plotted? What are the value arrays? Array of Arrays?

Post the full chart JSON and I'll get you a demo working. Since your chart is dynamic you can grab the rendering JSON by right clicking on the chart, clicking the View Source option, then copying the contents from the parsed JSON tab.

EDITED NEW ANSWER IN RESPONSE TO FIRST COMMENT BELOW:

Array of arrays does not automatically fit the graph width on scaleX. The reason for this is you are requesting to plot something much more specific than a single dimensional array. So you are right to set the minValue and maxValue.

The main issue is the step value. Since you have defined a step that is less precise than values in the minvalue or maxvalue you must make it match the same precision. For example you put two decimals, execpt your step is set to step:.2 which is only of precision of one decimal. Change that precision to two. step:.01 || .02 to get the desired results you are looking for.

One quick side note. You have two scale-x objects. They get merged internally, but this is dangerous because the lower one will override the first. If you have a large JSON this becomes harder to debug.

demo link