Look at these Gios drop outs
 

Interesting.

http://bike-vintage.eu/ebay/FOTO/gios2/foto06.jpg

Those look pretty kludgy. I wonder what the purpose of such a design is?

I think Geos also offered track style bolt on drop outs for time trial purposes. I seem to remember them having multiple hanger options back in the day. This is coming from something I've heard on earlier internet threads regarding gios.

Lets you modify chainstay length. Seems a little gimicky (and I'd have a hard time fully trusting a dropout that bolts on like the cleat on my shoe).

Oh, and the frames are still available from excelsports:
http://www.excelsports.com/new.asp?p...ajor=1&minor=1

there are tons of bolt on dropouts nowadays. I don't really understand why you would do that on a bike like that. Now it's for IGH and fixed applications.

The design affords the chainstay/wheelbase adjustibility of horzitonal dropouts while maintaining a fixed chain gap, which is critical for the optimium performance of indexed shifting systems.

Replaceable dropouts have been in use for a long time on ATB frames and are reliable. You just use a little blue Loctite on the threads, to ensure they don't loosen.

Whether or not it's gimmicky is a matter of personal preference, however I suspect these frames will have higher than normal resale value a decade or so down the road. I predict they will become highly sought fixie/SS fodder by virtue of being one of the few frames from the era that provide the ability to adjust chain tension.

It gives you both replaceable vertical dropouts (really only important on the drive side) and fore-aft adjustability to adjust wheelbase. Like having a combo vertical/horizontal dropout. I've never been able to feel any difference in that little bit of wheelbase adjustability but some folks swear they can.

It may not look clean and sleek though it does look cool in its own right, wish more older frames had replaceable drop outs.. I've got a nice frame I can't really do anything with cause the hanger got all messed up in a crash.. heck I cant even single speed/fix it cause of the vertical drop outs!

Sure ya can!

http://www.whiteind.com/rearhubs/singlespeedhubs.html

I owned a Gios Compact Pro for about 3 years, and the replaceable/adjustable dropouts were one of its really nice features. First, if you break a dropout, they are easy and inexpensive to replace. Second, you can adjust the chainstay length by about 1-1.5 cm. Shorter stays make the bike more responsive and quicker; lengthening the stays makes for a more stable, comfortable ride. I kept mine fully extended.

Actually, according to the catalog I have, adjustability is 8mm. And to the uninitiated, let it be known that Gios came up with this setup 25 years ago, it may look like old hat now, but imagine ajdustable, changeable, vertical (as opposed to horizontal) dropouts back in '84.