Dating site for sr
The rear derailleur freewheel/cassette and chainwheels are probably the first to be changed on a bike.On a vintage bike in excellent condition (that apparently had a lonely existence in a garage) all of the components likely are original.Of course, all this assumes the bike has the original component.The most likely components to be original are the stem, handlebars, seatpost, and brakes.Pull the lever and look inside the top of the lever arm for a code such as "1084." Dia-Compe extension levers (yuck) also tend to have date codes on the side that faces the brake hood.I have a set of Dia-Compe mountain levers where if you pull the lever all the way, a piece of the lever is exposed, which has a clock-type date code.For old Treks, 27.2 is the most common, but for other bikes the diameters can range from 25mm to 33mm.The rear derailleur can often be dated to a year or two by referring to the book "The Dancing Chain - History and Development of the Derailleur Bicycle", by Frank Berto, 3rd edition 2009.
However, a Gran Compe set of calipers had no markings. For example, 1182 means the 11th week of the year 1982.
Dia-Compe cantilever brakes don't appear to have a date code, but supposedly the 981, 983, 986 brakes were first introduced in 1981, 1983, 1986, etc.
Following Ben's lead - I checked three sets of Dia-Compe G calipers and all have the four-digit date code on the back of one of the arms.
This makes dating the components an interesting archeological investigation, but one not necessarily related to the date of the bike. Trek owner Larry Osborn made this observation, and suggested this as a supplementary way of dating a Trek (and other bikes as well).
Fueled by this first realization, and with the help of other bike folks, Larry and I have sorted out other codes (a project still ongoing).
The Appendix gives dates of initial manufacture for the vast majority of derailleurs made from 1920 to 1999.