To reproduce: 
- add RadRibbonBar with several CommandTabs and private void Form1_Load(object sender, EventArgs e) { radRibbonBar1.Expanded = false; } 
- add RadButton and on its Click event use: private void radButton1_Click(object sender, EventArgs e) { radRibbonBar1.CommandTabs[0].Visibility = Telerik.WinControls.ElementVisibility.Collapsed; } 
As a result the CommandTab is collapsed but some empty space remains.

Workaround: private void radButton1_Click(object sender, EventArgs e) { radRibbonBar1.CommandTabs[0].Visibility = Telerik.WinControls.ElementVisibility.Collapsed; this.radRibbonBar1.Expanded = !this.radRibbonBar1.Expanded; this.radRibbonBar1.Expanded = !this.radRibbonBar1.Expanded; }