Do you only have those characters at the end of your string? you could simply use REPLACE or if you just want to eliminate the last ones, there's a more complex approach.

Here are some examples:

DECLARE @String char(9), @Final varchar(9)

SELECT @String = 'asdf'

SELECT @Final = @String

PRINT @Final + @String

SELECT @Final = LEFT( @String, 10/*Length + 1*/ - PATINDEX( '%[^]%', REVERSE(@String)))

PRINT @Final + @String

SELECT @Final = REPLACE(@String, CHAR(9), '')

PRINT @Final + @String