To reproduce:

Add a RadChartView and add some data. Add a RadRangeSelector and set the AssociatedControl to be the chart.  On a button click set the Start and EndRange of the range selector. You will see in the chart that the range will not update.

Workaround:

Update the view manually:

this.rangeSelector.StartRange = 30;
this.rangeSelector.EndRange = 60;
(this.rangeSelector.RangeSelectorElement.AssociatedElement as IRangeSelectorElement).UpdateAssociatedView();