Not so much to tighten chains on SS bikes, but more to mess with BB heights (and chainstay measurements if you really want to I guess). There's this for a BB30 shell http://www.universalcycles.com/shopping/product_details.php?id=41682 They state 16mm of fore/aft movement, so theoretically, you could use one of these to drop your bb height 8mm. Not huge, but couple that with some selective headset and tire combos you might be able to get an appreciable measurement out of it. Any reason why this wouldn't work? And is there anything comparable for a threaded BB shell?