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I am absolutely agree with previous comment.
This is a bad practice to change tab width to any value. It should be 8 chars long. Period.
You should separate indent stop and tab stop as separate settings.
Imagine we use both tabs and spaces to indent.
If John uses 8-column tab and uses 4-column indents then his code will look like this:
     1st indent with 4 spaces
        2nd indent with 1 tab (his editor settings set to replace spaces with tabs)

Now I open this text in awesome ST2 :)
My settings are:
// The number of spaces a tab is considered equal to
// Because I want 4-column indent
"tab_size": 4,

And what do i see? This text:
    1st indent with 4 spaces
    2nd indent with 1 tab (Bah!)

Actually solution is pretty straightforward: add setting
"indent_size": 4,
and you are done (i hope).
Only this missing feature stops me from using ST2 and purchase it (I have never imagined i would PURCHASE text editor for Linux with its tons of FREE editors).
Currently I use Kate under Ubuntu.
Actually I attach image with Kate indentation settings just to be more specific on this issue.