Yesterday as I was removing the cranks from my project bike (and some skin from the knuckle of the first finger of my right hand) I noticed that the right (drive-side) crank was much tighter than the left crank. As I washed and bandaged my knuckle, it occured to me that this is usually the case. Now understand, I'm talking about a standard three piece cotterless crankset which requires a crank puller to remove the cranks. I suspect that pedal forces tend to tighten the bolt on the right side crank, and loosen the left side bolt.

Am I on the right track or is this just a crank theory?

Nope.If they are put on correctly, equally tight,they stay that way.Often in original instllation the left for whatever reason gets put on not tight enough. Riding may aggravate the problem and the crank arm gets damaged.A damaged arm will tend to be self loosening thereafter.Loctite on the bolt or a shim on the taper may be a fix(temporary) if the taper is indeed damaged.

I figured you could let me know if it was applesauce. Thanks, Pokey.

For what it's worth, the left crank seemed plenty tight. It's just that the right was noticeably tighter. There is no apparent damage to the crank or spindle. It wouldn't matter anyway, as I was pulling the cranks preparatory to replacing the bottom bracket and installing a new (singlespeed) crankset.