I have my new mystery french frame home from the shop after emergency surgery to remove a stuck stem and chase out the steerer threads.
The question is: what do I have?
The bike was believed to be a Motobecane frame, constructed from a full 531 db tubeset. The frame had been repainted at one time, destroying the decals and identifying marks. Seller was not the original owner and wasn't the one who had the frame painted. There are english language 531 stickers on frame and fork. (But how honest was the person who did the repaint?) It also has top tube brake cable guides, bb cable guides and one set of bottle bosses. Of course brazeons may have been added during the repaint. BB guides are identical to Campy guides on my Marinonni. For my own piece of mind, I'd like to figure out as much as we can about what the bike is. (I bought her for the components, so even if the frame is of lesser quality, I got my money's worth).
CLUES:
Seat tube is 26.4 mm, BB shell and pedal holes on cranks are french threaded. Lug work is roughly finished. Lugs are smooth edged with short points on top, large spoons on the underside of the tubes. No sign of head badge rivet holes. Tubing is seamless, the steerer is seamless and unrifled, and the entire frame is fairly light. Bottom bracket has no brand mark, but has a large ugly longitudinal seam on the bottom, along with a small drain hole. Mitering seems adequate, although the down tube protrudes 1/2 and inch into the bb.
There is a serial number plate riveted/pinned to the bottom bracket shell. Serial # is 2638630. Dropouts are horizontal Simplex forgings with an integral hanger. Hanger is unthreaded french style without a stop. Dropouts have one set of eyelets, frame has touring/mild racing geometry (17.5 inch chainstays, 41.5 inch wheelbase). No signs of chrome on the frame. Brake reach is longish, with a Universal 61 centerpull mounted on the rear with pads near the middle of the slots.
CONCUSIONS:
Based on the dropouts, seat post size and threading, I'm satisfied the bike is French, and with the seamless tubing and forged dropouts, of respectable quality.
Can anyone give a guess on the maker and model with this information?
Does anyone have a simple method of determining whether tubing is double butted or not? (Tapping along the top tube changes timbre as you near the center of the tube, but that may be due to distance from the lug work.)
All right folks, you have your assignment, let's hit the streets. And let's be careful out there.
Tom Adams, Kansas City