Originally Posted by
ItsJustMe
Well, the main reason is that the frame tube is so thin that you'll probably only get one or two threads cut in it, and as soon as you even try to tighten it you'll just rip the threads right out. You need a threaded boss.
I dunno, new Schwinn Varsity might have a pretty thick walled seat tube
[MENTION=397038]12strings[/MENTION]: Measure the seattube diameter and subtract the seatpost diameter, then divide by two. If it's at least 4mm then I'd probably go for it.
Don't tighten the bolts very tight, use some red Loctite.