To reproduce:
this.radChartView1.AreaType = Telerik.WinControls.UI.ChartAreaType.Polar;
RadarLineSeries series = new RadarLineSeries(new SizeF(8f, 8f));
series.DataPoints.Add(new CategoricalDataPoint(0.0, "Coding"));
series.LegendTitle = String.Format("Coding");
series.BorderWidth = 2;
radChartView1.Series.Add(series);
series.PolarAxis.Minimum = 0d;
series.PolarAxis.Maximum = 0.0;
series.PolarAxis.TickLength = 4;