Regarding Jerry Moos' TA comment" "...The 152 BCD Criterium rings I acquired in this purchase are the type with which the inner ring bolts to a 152 BCD circle in the outer ring (PB: see A below). But I also have a Criterium "Adapter" with no teeth itself, which bolts to the arm, with both rings bolting to this adapter (PB: see B below) The possible range of rings is the same either way, so I'm puzzled as to why TA felt it necessary to implement this bolt circle two different ways...."
My understanding is that Jerry refers to
A: ref:ch205 "criterium" outer chainwheel
B: ref:175 "professionnel" "adapteur" for ref:204/206"criterium" pattern chainwheels; double or triple
Both shown on http://www.blackbirdsf.org/
if you are a racer or someone interested in changing chainrings quickly without unmounting the crankarm and pedal, then the TA professionnel adapteur is for you. If you are someone setting up bike gearing and sticking with it, like a non-racer, then the adapteur isn't necessary. If you look at a lot of old racing pictures, you will see many racers using these adapteurs.
Peter "two down, one to go" Brueggeman La Jolla California USA pbrueggeman(AT)ucsd.edu