Framebuilders - Pardon my stupidity, but...

How does one "officially" measure chainstay length? Is it the length from the bb to the dropout when measured parallel to the top tube (looking down from above), or is it the actual length of the chainstay measured parallel to the chain stay itself?

Thanks!

There is no "official" way. Most builders measure on an angle along the length of the stay itself which as you know, does not reflect how far back the wheel is along the centerline of the bike. I think this convention was born from practicality since it's easy to grab a steel tape and measure along the length of the stay. That said, if you have one of those super Anvil frame fixtures it it has a scale of some sort built in to give you the measurement along the centerline (I believe).

One thing to keep in mind if you are using the "measure along the stay" method is that bottom bracket drop will effect the chain stay length; more drop makes the stays longer for any given "effective" chain stay length.

Long chain stays are generally a good thing unless you are doing crits and such. By putting the wheel further out back more of the total weight is transfered to the front wheel which helps even up weight distribution.

Center of bottom bracket to the the center of rear wheel; with the wheel placed in its normal position not all the way back in the drop outs.