In the early '80's a feature of the Shimano 600 "arabesque" group was a self-extracting bolt which eliminated the need for a crank extractor; to tighten it, you would tighten the allen key like any other crankset, but to remove the cranks, you just loosened that one allen key, hence the ads at the time which called it a "one-key" system. However, it only lasted a couple of years, which leads me to believe that there must have been problems ... otherwise, it was a cool system, and should have lasted as part of their product line.

Here's my suspicion as to the problem, which I pose as a question: do they tend to loosen over time? I've got a set mounted on my Austro-Daimler Starleicht; after a short ride a couple of weeks ago, I had to tighten the loose left side. Since the cranks were only recently mounted, I wrote it off to my own sloppiness when I mounted them, tightened everything, and forgot about it. Then, at the top of a long climb a couple of days ago, the left crank had loosened up again, even though I'd gone over the whole bike with the wrench set before I took off on the ride.

Is this phenomenon the reason Shimano gave up on the "one-key" concept?