Tom,
This is addressed by Jobst Brandt in the rec.bicycles FAQ at
http://draco.acs.uci.edu/
Selective quotes:
"Crank failure from "over-tightening" is caused by the re-tightening of previously properly installed cranks." (from Paragraph 4)
"Because cranks squirm farther up the taper when stressed highly, the unwitting mechanic believes the screw got loose, rather than that the crank got tighter. By pursuing the crank with its every move up the spindle, ultimately the crank will split." (from Paragraph 8)
Lee Berg Palo Alto, Calif.
Tom Dalton wrote:
>
> All kidding aside, I have never heard of anyone
> recommending against retightening crank bolts. In
> fact, the standard practice is to retighten crank
> bolts at least once in the first couple hundred miles
> after installation. I've always applied this to new
> and used crankarms. I've also noticed that the amount
> of retightening needed on high-end cranks is far less
> than on mid-grade cranks. Why do you describe
> retightening as a "no-no"?