How to cleanup tabs with vim, adjust sts and sw?

I created c++ files in vim with these tab settings

set sts=4
set sw=4

meanwhile i use

set sts=3
set sw=3

and want to change all the files. Is this possible?

EDIT

I go with indent, a few other options come handy.

I don't know of an automated way to do this with vim, but there's no reason you can't open up each of those files individually and use :retab! to have them use your new settings.

If you want to re-indent a whole bunch of files at once, you may look into something like GNU Indent.

Not VIM-specific, but if you want to batch process all the source files in one shot, the indent command line tool is incredibly useful.