It seems to me that the Question is pretty straightforward:
"How to Achieve Client Side Sorting without Postback" but what the user (and myself) is really trying to achieve is re-sorting the array without retrieving the data again.
Both of the responses here send the user to threads or examples that insist on do declarative binding which is just another way of getting the data again.
It would appear to me that there is no Built in way to do this with Telerik Rad Controls. I suspect this has to do with the fact that the entire Grid is ajaxified and as such requires a postback?
Can we please get an Admin person that really understands this to give us a straightforward answer?