This solution will help in more ways than just the bar chart labels. If you use Crystal's option to Customize the group name, it will not only make them appear on the bar chart label but the new group name will appear in the group tree.
Here's the solution:
1) Select Group Expert under the Report Menu (you can also right-click the Group if in design mode and scroll down to Change Group)
2) Click the Options... button
3) Go to the second tab labelled Options
4) Click in the box labelled "Customize Group Name Field"
5) Then either select the top radio button "Choose from Existing Field" or the second radio button "Use Formula..." in which you can combine fields using formulas to show what you want.
This works great in Crystal so reply if you have problems.