Originally Posted by
Numberfourson
I own two 1973 Zeus Professionals and discovered they are two different threads.
I bought a few pairs of Shimano SPD pedals thinking if I used the same pedals on differing bikes I wouldn't need a set of shoes for toe clips. The pedals threaded easily into one crankset but not the other.
FWIW, Zeus crank arms will have "BSC" stamped in the back of the arm to indicate English thread. If there is no mark, it's likely metric (aka "French") thread, unless a previous owner re-tapped them to English.