Nick,
Nice find. We sold some Zeus bikes back in the 70s. Zeus suffered from the Rodney Dangerfield syndrome - they couldn't get no respect among the cognoscenti. If you got past the "all Campy" vanity factor Zeus bikes and components offered a lot of bang for the buck.
The bikes were more or less a poor man Cinelli and the components were far more than cheap Campy knockoffs! For example, Zeus headsets were better made than Campys; we never had bottom cup/fork crown race indentation problems with them.
The rims are the original Akront brand made famous in motorcycle racing. They have distinctive serrations in the sidewalls (to better hold watter when wet). From the early 70s on these bikes came with Cinelli 1a stems.
Up through the late 60s Zeus produced some bikes made of Reynolds "A Quality" tubing. Reynolds made "A Quality" and "B Quality" seamless tubing drawn in the same manner as 531 but made of lower strength carbon steels rather than the manganese molybdenum alloy steel used in 531.
I suspect that Zeus switched to French made Durifort tubing when Reynolds discontinued "A Quality" tubing. Durifort had similar mechanical properties to Reynolds "A Quality" tubes.
The frame tubes and treads were all made to the French metric standards.
The top Zeus model in the early 70s was the Criterium (I think). It had Durifort forks and stays with butted Reynolds 531 main tubes. This was a common practice on many better quality French bikes too. Theses bikes cames with 1/3 of the forks and rear stays chrome plated.
I can tell from the tire clearance crimps in your chainstays that they're made of Durifort tubing so there is a good chance that it has butted Reynolds 531 main tubes too.
What I've always found interesting in bike mythology of the 70s was that an "all Reynolds 531" bike was perceived to have a lighter frame than one made of some other alloy steel tubing.
From the late 60s through at least the mid 80s many if not most European production built 531 frames were made of 7/10 butted main tubes. That means the thicker butted ends of the main tubes had a 1.0mm wall thickness while the thinner sections were 0.7mm wall thickness.
Butted Durifort tubing was 7/10 too so there was no difference in weight (or ride) and only about a 25%-30% reduction in strength. "Heavy gage" Columbus SP tubing had the same dimensions! Butted Durifort and Vitus 172 had about the same wall thickness as Columbus SP! So much for the perception of lightness. The marketers did a good job!
One of the reasons for using 7/10 wall thickness main tubes was that less skilled employees could be used for brazing the frames with less concern for overheating the steel tubing. Even when the thicker tubing was overheated there was sufficient material to provide a safety factor in tube strength.
When Zeus switched from Cinelli style fork crowns to their investment cast ones with ZEUS 2000 molded in they also started offering all Reynolds 531 frames.
Here's a Bike Forums link with some good and misinformation about Zeus bikes:
http://www.bikeforums.net/
BTW, most CR cognoscenti know this but on a "double butted" frame, only the top and down tubes were double butted! Seat tubes were only butted at the bottom bracket end. There have been occasional frames made with double butted seat tubes but that was not the norm. Also frames accidentally (or carelessly) built with a down tube used for a seat tube or a seat tube brazed in upside down with the butted end up! ;-(
Chas. Colerich Oakland, CA USA
Nicholas Brunner wrote:
> I just picked up what appears to be a late 60's Zeus locally. The frame is
> made from Durifort metric tubing. It was given an average paint job in
> orange at some point, but looks good from a few feet away. The drivetrain
> is Zeus Criterium, and the brakes were upgraded at some point to 2000
> centerpulls. It came with an age appropriate nutted Cinelli stem drilled
> for the cable stop. The bike is surprisingly light. I've seen limited
> information on Zeus in the archive, so decided to add a link for some
> pictures.
>
> http://www.flickr.com/
>
> Nick Brunner
> Brooklyn, NY