Here's some thoughts as I was tearing down the bike and inspecting the frame.
1) The Circuit appears to be original except for the seat, brake pads, bar tape and wheel skewers (wheel skewers? WTF happened to the original wheel skewers??). An interesting item of note is the Rigida HLC2000 rims laced to Sante hubs. The Schwinn catalogs at http://www.trfindley.com/pg_schwinn_cats.htm indicate OEM rims were Wolber Tx Profil. Makes sense, back in those days every other OEM rim was Wolber. I don't recall a whole lot of bikes being spec'ed with Rigida rims. Of course, I've also found mfr. spec sheets are like lane striping in Asian countries - just a suggestion and not the rule. Take for example, my 1987 Allez. The catalog and spec sheelts say (guess what?) Wolber Alpine rims, but mine came with Saturae. I've seen a handful of examples since that have the Alpines on them, just as I've also seen examples of the Circuit with the Tx Profils. My guess would be manufacturers using up old stock or supply/quality problems from the OEM that cause these deviations from the intended specs. I looked through a few spec sheets from the 1987 Schwinn catalogs and there were a few models spec'ed with Rigida rims, although not the HLC2000 model - (want to bet some of 'em came out of the Schwinn factory with Wolber instead? :) So I would guess Rigida maybe sent Schwinn a wrong batch of rims and to save on some costs, Schwinn just used up the overstock Rigidas on a few Circuits they pumped out. Anyone care to comment on Rigida rims and specifically the HLC2000's? I have absolutely zero information on these other than they look as ugly as any other 20 year old rim with the anodization worn off in patches on the braking surface.
2) Tange Aero tubing. The Columbus seat tube decal "Tretubi" indicates 3 main tubes of Columbus SL/SP. The rest, including the fork, I assume are this mysterious Tange Aero tubing. I can't find any information on it other than the odd "Aero-style" bike (Panasonic) made with this tubing and some references to BMX frame/forks. I wonder if this was the same deal as OEM parts - namely Schwinn had some of this extra stuff lying around and to offset the cost of using Columbus main tubes used up the old stock of Tange Aero that would otherwise be collecting dust and spider eggs in a corner of the warehouse. Bikes did experience a huge price jump in 1988. Comparable models in my 1987 and 1988 buyer guide mags jumped as much as $200 from one year to the next. My '87 Allez was $599 MSRP that year. That same price in '88 would've got you a model one step down, the 105-equipped Sirrus, give or take 50 bones.
3) This bike is a paradox. The frame has a well above-average number of nicks, scratches, chips in the paint as well as a smattering of rust on the chrome forks and some serious buildup on the rear brake bridge. And oh man, the grease! Heinous gunky grease embedded in the paint everywhere. I'd give it a 5/10 for cosmetic condition. However, the components, aside from cosmetics, appear to be in excellent shape. BB and headset cups are pit-free and smooth. Hubs and pedals don't have any obvious binding or pitting in the races. Cassette cogs don't show any wear nor do the chainrings. I'd say 8/10 for the bike mechanically or as about as good as I've seen in a bike this age. Perhaps the previous owner(s) rode the bike for a season or two and put it away in a garage to collect shopwear scars. Kind of a shame, it's turning into a beautiful bike with a little TLC.
