My daughter had outgrown her mixte and she needed a new townie. This looked like a good candidate but first I wanted to convert it from its intended wheel size of 27” to a 650B for the comfort and to get clearance for fenders.
The Sugino Mighty Competition crankset that came affixed to the frame was no doubt original equipment on this ‘72ish bicycle . The Mighty is a top quality vintage component. Unfortunately, the BCD (bolt circle diameter) is very large at 144mm. (For more info on bolt circle diameter, check out the late great Sheldon Brown’s excellent explanation!)
I wanted to put a vintage crankset on this bike, but the Sugino’s 144mm would not permit chainrings small enough for how she plans to ride. So I needed to pick something generally period in a double or triple with a small bolt circle diameter.
Back when many production bicycles and their components were made in Europe, there were plenty of proprietary fittings. This was especially true with cranksets. Different manufacturers used different bolt circle diameters - not to mention spindle tapers and pedal or dust cap threading.
After a couple of fits and starts, I landed on and old SR triple with a BCD of 86mm. The 86mm pattern was originated by the French company, Stronglight, and picked up by the Japanese company SR (Sakae/Ringyo).
I have long appreciated the 86mm crankset. It can handle a ring as small as 28 teeth and works well as a double or triple. Unfortunately, the pattern did not catch on and after just a few years, both Stronglight and SR abandoned it. In an industry where everything old is new again the 86BCD crankset is on my list of things to take up again.