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?

Had it on one of my bikes since 1985. Never had a problem, and have ridden thousands of miles. Sounds like you may have a rounded crank arm or spindle.

They shouldn't loosen up. The explanation I heard was that self extracting cranks were just to convenient for thieves & simply lost favor with the buying public.

You can currently buy new bikes with the same sytem. Very popular also on folding bikes. What goes around comes around. Roger

The concept has been marketed by several companies over the years, including Campagnolo. I never had a problem with mine. I don't the reasons for it's demise, but I've heard Ollo Ollo's rationale stated on several occasions and it makes sense, even if it only part of the story.

I have one on my Mercian... still works great.

The 600 crank on my wife's Fuji mixte has them. The BB spindle is marked "for use with self-extracting bolts" or something to that effect. It looks like a perfectly ordinary ordinary spindle, otherwise. I think those bolts can be used on any crank with 22mm threads. They hold the arms on like any crank bolt, so I don't see how they could have a tendancy to loosen. The only difference is that they push the arms off when the bolts are backed out.

I agree with Dirtdrop; no logic to the loosening theory. The reason it fell out of favor was the weight of the HD dustcaps.

The only way I can see them loosening is due to the fact that you can't get anywhere near the same torque on the bolt as with a standard bolt head...that is, with a standard short Allen wrench - one with a longer handle may be different, but nevertheless there is no reason why they should undo if they done up nice and tight...

I use the same 3/8" drive ratchet, but with the appropriate bit. Sometimes I even use my torque wrench. You can't properly torque a crank bolt with a little allen key.

torque um to 25 foot pounds. I you don't have a torque elbow get a cheap torque wrench.

25 pounds is pretty hard, but not super hard

I'd guess that MajorA used a short Allen key to tighten the bolts.

Edit: Shimano sold a long Allen key plus cheater bar for use with the one-key release crank bolts.

You guess right. I'll check this bike with a torque wrench the next time I'm down at the co-op workshop. It makes sense that hand-torquing with just an Allen key wouldn't get things tight enough, as opposed to the force which can be applied by hand with a standard crank bolt wrench. Thanks, folks.