As part of reviving and restoring any vintage bicycle, it may become necessary to replace components with period correct counterparts. Replacing fasteners and other hardware can also present challenges, given not only their special purpose, but also their one-off threading, which may be French, not-so-French, Italian, and other threading anomalies. Over the last 10 years I have restored a number of vintage bicycles that presented challenges in both the component and hardware categories.
Huret derailleur
Simplex chain stay mounted bell crank derailleur
The mid-century Mercier Meca Dural that I restored a few years ago was fitted with an incorrect wheelset and rear derailleur. The Huret unit, depicted first, was installed on the bike’s vertical dropouts, yet this rear derailleur is designed for horizontal dropouts. This was an example of modifications made to the original bike, with bad results. The incorrect Huret derailleur mounted on the vertical drop-outs resulted in no chain wrap, and poor shifting. After seeing that the bike had also been modified with an incorrect and too large wheel size, I took to French eBay to source a NOS chainstay mounted Simplex bell crank derailleur – a component which was standard fare on vintage Mercier Meca Dural bicycles of this era.
When the NOS derailleur and shifter arrived, I rejoiced in how beautiful and functional this vintage component was. Searching foreign language sites broadens the scope of your endeavor, and may make the difference between success and failure.
Simplex was notorious for using oddball threading on its components. The 2nd photo above shows a Simplex shifter with M6 x .8 threading – instead of the standard M5 x .8 on all other shifter bolts of this era. I have a tap and die set of tools in my shop to use in the event that re-tapping is necessary. However, I try avoid this if replacement vintage components can be found with the original threading. 
Sometimes, things work out well, as was the case with this mid century mystery French mixte with Oscar Egg lugs. The Simplex components on this bike were clearly all original and worked perfectly once the bike was overhauled.
If you will need to add or replace fenders on a vintage bicycle I recommend exploring Velo-Orange, Rivendell, and Compass. These vendors offer different products and hardware from a variety of manufacturers, and you may be able to find just the right fender width and hardware for your application. Fender stays, bridge mounting hardware, and daruma and eyelet bolts are usually included in your purchase of new fenders. Meanwhile, I can’t think of any manufacturers today who are making a fender resembling these lightweight and well engineered steel fenders shown on this early 1980’s Meral, above. These fenders mount easily with the original hardware and work fine with a 650b conversion. They are an example of the unsurpassed beauty and utility of vintage components.
