Jan says:
A 1957 Cinelli S.C. with cottered Magistroni steel cranks has a tread of 120 mm. A typical Stronglight 49D crank with double chainrings has a tread of between 134 and 137 mm. The first-generation Campagnolo was a tad wider than that.
What are the BB shell widths involved? Are you looking at an original Cinelli? How can you document the originality of the components and the bike? Which Magistroni BB are you looking at? How did you determine the year of the bike? How have you documented the year of production? Are all the components original? How have you documented this? How did you measure the tread? How do you explain the 3 mm difference in the 'typical' Stronglight set-ups? What is the comparable range for Campagnolo? Please don't tell me that you are using one single reference to make your determinations. If I am not mistaken, using very rudimentary measurement tools, my heavily-used late 50's Campagnolo crank equipped Italian bike with 70 mm shell width measures 135 mm from pedal/crank interface to crank/pedal interface. My well-used 1963 Campagnolo crank equipped Italian bike with 70 mm shell width and less common Campagnolo 3/16" bearing size BB measures 133 mm. Given the rudimetary nature of my measuring devices, I guess that my my measurements could readily be out by up to 6-7%, but since these measurements come close to those that Jan measured, I will take them to be correct.
I wrote this last sentence to show how research is often handled and to demonstrate whyit is best not to speak in absolutes.
Steven Maasland
Moorestown, NJ
USA