Fortunately, there is a good visual cue to discriminate the 144 from the 151. With the 144, the inner edge of the mounting bolt is only about 1 mm from the shoulder on the spider. With the 151 mm circle, the same measurement is about 4.5 mm, or 3/16" inch. The eye picks this up very easily. This is particularly easy to spot if you just look at the chainring, which will have the big gap between the inner edge and the mountinb bolt for the 151 circle, and almost nothing for the 144. The shoulder on the web, and the inner diameter of the inside reinforcement on the chainring, are the same for both series.
A couple of other notes: --> I think that the transition on the ROAD cranks was about 1964 +/1 a year or so. Track cranks continued the 151 circle for many years. --> 151 road rings are much less common. Downright rare, even. Particularly in smaller sizes (44 was the smallest offered, I believe), because most riders of the day used half-step with sets like 49/52 or 47/50.
Enjoy! Harvey Sachs McLean VA, where the weekend was wonderful for riding
At 06:14 PM 10/22/2000 -0400, Philcycles@aol.com wrote:
>In a message dated 10/22/0 10:09:29 PM, firstname.lastname@example.org writes:
> >Standard Campagnolo bolt circle diameter (BCD) is 144 mm. Minimum standard
> >ring is 42 teeth, there might have been others down to 41.
>The original Record cranks were 151mm. The 144mm cranks minimum was 41 teeth
>but they are very rare. Both Campy and TA made them.
>Phil (staring at a Campy 41 tooth ring) Brown